-\r
- ------------------------------------------------------------\r
- This is the second part of a two part file.\r
- This is a list of changes to pccts 1.33 prior to MR13\r
- For more recent information see CHANGES_FROM_133.txt\r
- ------------------------------------------------------------\r
-\r
- DISCLAIMER\r
-\r
- The software and these notes are provided "as is". They may include\r
- typographical or technical errors and their authors disclaims all\r
- liability of any kind or nature for damages due to error, fault,\r
- defect, or deficiency regardless of cause. All warranties of any\r
- kind, either express or implied, including, but not limited to, the\r
- implied warranties of merchantability and fitness for a particular\r
- purpose are disclaimed.\r
-\r
-\r
-#153. (Changed in MR12b) Bug in computation of -mrhoist suppression set\r
-\r
- Consider the following grammar with k=1 and "-mrhoist on":\r
-\r
- r1 : (A)? => ((p>>? x /* l1 */\r
- | r2 /* l2 */\r
- ;\r
- r2 : A /* l4 */\r
- | (B)? => <<q>>? y /* l5 */\r
- ;\r
-\r
- In earlier versions the mrhoist routine would see that both l1 and\r
- l2 contained predicates and would assume that this prevented either\r
- from acting to suppress the other predicate. In the example above\r
- it didn't realize the A at line l4 is capable of suppressing the\r
- predicate at l1 even though alt l2 contains (indirectly) a predicate.\r
-\r
- This is fixed in MR12b.\r
-\r
- Reported by Reinier van den Born (reinier@vnet.ibm.com)\r
-\r
-#153. (Changed in MR12a) Bug in computation of -mrhoist suppression set\r
-\r
- An oversight similar to that described in Item #152 appeared in\r
- the computation of the set that "covered" a predicate. If a\r
- predicate expression included a term such as p=AND(q,r) the context\r
- of p was taken to be context(q) & context(r), when it should have\r
- been context(q) | context(r). This is fixed in MR12a.\r
-\r
-#152. (Changed in MR12) Bug in generation of predicate expressions\r
-\r
- The primary purpose for MR12 is to make quite clear that MR11 is\r
- obsolete and to fix the bug related to predicate expressions.\r
-\r
- In MR10 code was added to optimize the code generated for\r
- predicate expression tests. Unfortunately, there was a\r
- significant oversight in the code which resulted in a bug in\r
- the generation of code for predicate expression tests which\r
- contained predicates combined using AND:\r
-\r
- r0 : (r1)* "@" ;\r
- r1 : (AAA)? => <<p LATEXT(1)>>? r2 ;\r
- r2 : (BBB)? => <<q LATEXT(1)>>? Q\r
- | (BBB)? => <<r LATEXT(1)>>? Q\r
- ;\r
-\r
- In MR11 (and MR10 when using "-mrhoist on") the code generated\r
- for r0 to predict r1 would be equivalent to:\r
-\r
- if ( LA(1)==Q &&\r
- (LA(1)==AAA && LA(1)==BBB) &&\r
- ( p && ( q || r )) ) {\r
-\r
- This is incorrect because it expresses the idea that LA(1)\r
- *must* be AAA in order to attempt r1, and *must* be BBB to\r
- attempt r2. The result was that r1 became unreachable since\r
- both condition can not be simultaneously true.\r
-\r
- The general philosophy of code generation for predicates\r
- can be summarized as follows:\r
-\r
- a. If the context is true don't enter an alt\r
- for which the corresponding predicate is false.\r
-\r
- If the context is false then it is okay to enter\r
- the alt without evaluating the predicate at all.\r
-\r
- b. A predicate created by ORing of predicates has\r
- context which is the OR of their individual contexts.\r
-\r
- c. A predicate created by ANDing of predicates has\r
- (surprise) context which is the OR of their individual\r
- contexts.\r
-\r
- d. Apply these rules recursively.\r
-\r
- e. Remember rule (a)\r
-\r
- The correct code should express the idea that *if* LA(1) is\r
- AAA then p must be true to attempt r1, but if LA(1) is *not*\r
- AAA then it is okay to attempt r1, provided that *if* LA(1) is\r
- BBB then one of q or r must be true.\r
-\r
- if ( LA(1)==Q &&\r
- ( !(LA(1)==AAA || LA(1)==BBB) ||\r
- ( ! LA(1) == AAA || p) &&\r
- ( ! LA(1) == BBB || q || r ) ) ) {\r
-\r
- I believe this is fixed in MR12.\r
-\r
- Reported by Reinier van den Born (reinier@vnet.ibm.com)\r
-\r
-#151a. (Changed in MR12) ANTLRParser::getLexer()\r
-\r
- As a result of several requests, I have added public methods to\r
- get a pointer to the lexer belonging to a parser.\r
-\r
- ANTLRTokenStream *ANTLRParser::getLexer() const\r
-\r
- Returns a pointer to the lexer being used by the\r
- parser. ANTLRTokenStream is the base class of\r
- DLGLexer\r
-\r
- ANTLRTokenStream *ANTLRTokenBuffer::getLexer() const\r
-\r
- Returns a pointer to the lexer being used by the\r
- ANTLRTokenBuffer. ANTLRTokenStream is the base\r
- class of DLGLexer\r
-\r
- You must manually cast the ANTLRTokenStream to your program's\r
- lexer class. Because the name of the lexer's class is not fixed.\r
- Thus it is impossible to incorporate it into the DLGLexerBase\r
- class.\r
-\r
-#151b.(Changed in MR12) ParserBlackBox member getLexer()\r
-\r
- The template class ParserBlackBox now has a member getLexer()\r
- which returns a pointer to the lexer.\r
-\r
-#150. (Changed in MR12) syntaxErrCount and lexErrCount now public\r
-\r
- See Item #127 for more information.\r
-\r
-#149. (Changed in MR12) antlr option -info o (letter o for orphan)\r
-\r
- If there is more than one rule which is not referenced by any\r
- other rule then all such rules are listed. This is useful for\r
- alerting one to rules which are not used, but which can still\r
- contribute to ambiguity. For example:\r
-\r
- start : a Z ;\r
- unused: a A ;\r
- a : (A)+ ;\r
-\r
- will cause an ambiguity report for rule "a" which will be\r
- difficult to understand if the user forgets about rule "unused"\r
- simply because it is not used in the grammar.\r
-\r
-#148. (Changed in MR11) #token names appearing in zztokens,token_tbl\r
-\r
- In a #token statement like the following:\r
-\r
- #token Plus "\+"\r
-\r
- the string "Plus" appears in the zztokens array (C mode) and\r
- token_tbl (C++ mode). This string is used in most error\r
- messages. In MR11 one has the option of using some other string,\r
- (e.g. "+") in those tables.\r
-\r
- In MR11 one can write:\r
-\r
- #token Plus ("+") "\+"\r
- #token RP ("(") "\("\r
- #token COM ("comment begin") "/\*"\r
-\r
- A #token statement is allowed to appear in more than one #lexclass\r
- with different regular expressions. However, the token name appears\r
- only once in the zztokens/token_tbl array. This means that only\r
- one substitute can be specified for a given #token name. The second\r
- attempt to define a substitute name (different from the first) will\r
- result in an error message.\r
-\r
-#147. (Changed in MR11) Bug in follow set computation\r
-\r
- There is a bug in 1.33 vanilla and all maintenance releases\r
- prior to MR11 in the computation of the follow set. The bug is\r
- different than that described in Item #82 and probably more\r
- common. It was discovered in the ansi.g grammar while testing\r
- the "ambiguity aid" (Item #119). The search for a bug started\r
- when the ambiguity aid was unable to discover the actual source\r
- of an ambiguity reported by antlr.\r
-\r
- The problem appears when an optimization of the follow set\r
- computation is used inappropriately. The result is that the\r
- follow set used is the "worst case". In other words, the error\r
- can lead to false reports of ambiguity. The good news is that\r
- if you have a grammar in which you have addressed all reported\r
- ambiguities you are ok. The bad news is that you may have spent\r
- time fixing ambiguities that were not real, or used k=2 when\r
- ck=2 might have been sufficient, and so on.\r
-\r
- The following grammar demonstrates the problem:\r
-\r
- ------------------------------------------------------------\r
- expr : ID ;\r
-\r
- start : stmt SEMI ;\r
-\r
- stmt : CASE expr COLON\r
- | expr SEMI\r
- | plain_stmt\r
- ;\r
-\r
- plain_stmt : ID COLON ;\r
- ------------------------------------------------------------\r
-\r
- When compiled with k=1 and ck=2 it will report:\r
-\r
- warning: alts 2 and 3 of the rule itself ambiguous upon\r
- { IDENTIFIER }, { COLON }\r
-\r
- When antlr analyzes "stmt" it computes the first[1] set of all\r
- alternatives. It finds an ambiguity between alts 2 and 3 for ID.\r
- It then computes the first[2] set for alternatives 2 and 3 to resolve\r
- the ambiguity. In computing the first[2] set of "expr" (which is\r
- only one token long) it needs to determine what could follow "expr".\r
- Under a certain combination of circumstances antlr forgets that it\r
- is trying to analyze "stmt" which can only be followed by SEMI and\r
- adds to the first[2] set of "expr" the "global" follow set (including\r
- "COLON") which could follow "expr" (under other conditions) in the\r
- phrase "CASE expr COLON".\r
-\r
-#146. (Changed in MR11) Option -treport for locating "difficult" alts\r
-\r
- It can be difficult to determine which alternatives are causing\r
- pccts to work hard to resolve an ambiguity. In some cases the\r
- ambiguity is successfully resolved after much CPU time so there\r
- is no message at all.\r
-\r
- A rough measure of the amount of work being peformed which is\r
- independent of the CPU speed and system load is the number of\r
- tnodes created. Using "-info t" gives information about the\r
- total number of tnodes created and the peak number of tnodes.\r
-\r
- Tree Nodes: peak 1300k created 1416k lost 0\r
-\r
- It also puts in the generated C or C++ file the number of tnodes\r
- created for a rule (at the end of the rule). However this\r
- information is not sufficient to locate the alternatives within\r
- a rule which are causing the creation of tnodes.\r
-\r
- Using:\r
-\r
- antlr -treport 100000 ....\r
-\r
- causes antlr to list on stdout any alternatives which require the\r
- creation of more than 100,000 tnodes, along with the lookahead sets\r
- for those alternatives.\r
-\r
- The following is a trivial case from the ansi.g grammar which shows\r
- the format of the report. This report might be of more interest\r
- in cases where 1,000,000 tuples were created to resolve the ambiguity.\r
-\r
- -------------------------------------------------------------------------\r
- There were 0 tuples whose ambiguity could not be resolved\r
- by full lookahead\r
- There were 157 tnodes created to resolve ambiguity between:\r
-\r
- Choice 1: statement/2 line 475 file ansi.g\r
- Choice 2: statement/3 line 476 file ansi.g\r
-\r
- Intersection of lookahead[1] sets:\r
-\r
- IDENTIFIER\r
-\r
- Intersection of lookahead[2] sets:\r
-\r
- LPARENTHESIS COLON AMPERSAND MINUS\r
- STAR PLUSPLUS MINUSMINUS ONESCOMPLEMENT\r
- NOT SIZEOF OCTALINT DECIMALINT\r
- HEXADECIMALINT FLOATONE FLOATTWO IDENTIFIER\r
- STRING CHARACTER\r
- -------------------------------------------------------------------------\r
-\r
-#145. (Documentation) Generation of Expression Trees\r
-\r
- Item #99 was misleading because it implied that the optimization\r
- for tree expressions was available only for trees created by\r
- predicate expressions and neglected to mention that it required\r
- the use of "-mrhoist on". The optimization applies to tree\r
- expressions created for grammars with k>1 and for predicates with\r
- lookahead depth >1.\r
-\r
- In MR11 the optimized version is always used so the -mrhoist on\r
- option need not be specified.\r
-\r
-#144. (Changed in MR11) Incorrect test for exception group\r
-\r
- In testing for a rule's exception group the label a pointer\r
- is compared against '\0'. The intention is "*pointer".\r
-\r
- Reported by Jeffrey C. Fried (Jeff@Fried.net).\r
-\r
-#143. (Changed in MR11) Optional ";" at end of #token statement\r
-\r
- Fixes problem of:\r
-\r
- #token X "x"\r
-\r
- <<\r
- parser action\r
- >>\r
-\r
- Being confused with:\r
-\r
- #token X "x" <<lexical action>>\r
-\r
-#142. (Changed in MR11) class BufFileInput subclass of DLGInputStream\r
-\r
- Alexey Demakov (demakov@kazbek.ispras.ru) has supplied class\r
- BufFileInput derived from DLGInputStream which provides a\r
- function lookahead(char *string) to test characters in the\r
- input stream more than one character ahead.\r
-\r
- The default amount of lookahead is specified by the constructor\r
- and defaults to 8 characters. This does *not* include the one\r
- character of lookahead maintained internally by DLG in member "ch"\r
- and which is not available for testing via BufFileInput::lookahead().\r
-\r
- This is a useful class for overcoming the one-character-lookahead\r
- limitation of DLG without resorting to a lexer capable of\r
- backtracking (like flex) which is not integrated with antlr as is\r
- DLG.\r
-\r
- There are no restrictions on copying or using BufFileInput.* except\r
- that the authorship and related information must be retained in the\r
- source code.\r
-\r
- The class is located in pccts/h/BufFileInput.* of the kit.\r
-\r
-#141. (Changed in MR11) ZZDEBUG_CONSUME for ANTLRParser::consume()\r
-\r
- A debug aid has been added to file ANTLRParser::consume() in\r
- file AParser.cpp:\r
-\r
- #ifdef ZZDEBUG_CONSUME_ACTION\r
- zzdebug_consume_action();\r
- #endif\r
-\r
- Suggested by Sramji Ramanathan (ps@kumaran.com).\r
-\r
-#140. (Changed in MR11) #pred to define predicates\r
-\r
- +---------------------------------------------------+\r
- | Note: Assume "-prc on" for this entire discussion |\r
- +---------------------------------------------------+\r
-\r
- A problem with predicates is that each one is regarded as\r
- unique and capable of disambiguating cases where two\r
- alternatives have identical lookahead. For example:\r
-\r
- rule : <<pred(LATEXT(1))>>? A\r
- | <<pred(LATEXT(1))>>? A\r
- ;\r
-\r
- will not cause any error messages or warnings to be issued\r
- by earlier versions of pccts. To compare the text of the\r
- predicates is an incomplete solution.\r
-\r
- In 1.33MR11 I am introducing the #pred statement in order to\r
- solve some problems with predicates. The #pred statement allows\r
- one to give a symbolic name to a "predicate literal" or a\r
- "predicate expression" in order to refer to it in other predicate\r
- expressions or in the rules of the grammar.\r
-\r
- The predicate literal associated with a predicate symbol is C\r
- or C++ code which can be used to test the condition. A\r
- predicate expression defines a predicate symbol in terms of other\r
- predicate symbols using "!", "&&", and "||". A predicate symbol\r
- can be defined in terms of a predicate literal, a predicate\r
- expression, or *both*.\r
-\r
- When a predicate symbol is defined with both a predicate literal\r
- and a predicate expression, the predicate literal is used to generate\r
- code, but the predicate expression is used to check for two\r
- alternatives with identical predicates in both alternatives.\r
-\r
- Here are some examples of #pred statements:\r
-\r
- #pred IsLabel <<isLabel(LATEXT(1))>>?\r
- #pred IsLocalVar <<isLocalVar(LATEXT(1))>>?\r
- #pred IsGlobalVar <<isGlobalVar(LATEXT(1)>>?\r
- #pred IsVar <<isVar(LATEXT(1))>>? IsLocalVar || IsGlobalVar\r
- #pred IsScoped <<isScoped(LATEXT(1))>>? IsLabel || IsLocalVar\r
-\r
- I hope that the use of EBNF notation to describe the syntax of the\r
- #pred statement will not cause problems for my readers (joke).\r
-\r
- predStatement : "#pred"\r
- CapitalizedName\r
- (\r
- "<<predicate_literal>>?"\r
- | "<<predicate_literal>>?" predOrExpr\r
- | predOrExpr\r
- )\r
- ;\r
-\r
- predOrExpr : predAndExpr ( "||" predAndExpr ) * ;\r
-\r
- predAndExpr : predPrimary ( "&&" predPrimary ) * ;\r
-\r
- predPrimary : CapitalizedName\r
- | "!" predPrimary\r
- | "(" predOrExpr ")"\r
- ;\r
-\r
- What is the purpose of this nonsense ?\r
-\r
- To understand how predicate symbols help, you need to realize that\r
- predicate symbols are used in two different ways with two different\r
- goals.\r
-\r
- a. Allow simplification of predicates which have been combined\r
- during predicate hoisting.\r
-\r
- b. Allow recognition of identical predicates which can't disambiguate\r
- alternatives with common lookahead.\r
-\r
- First we will discuss goal (a). Consider the following rule:\r
-\r
- rule0: rule1\r
- | ID\r
- | ...\r
- ;\r
-\r
- rule1: rule2\r
- | rule3\r
- ;\r
-\r
- rule2: <<isX(LATEXT(1))>>? ID ;\r
- rule3: <<!isX(LATEXT(1)>>? ID ;\r
-\r
- When the predicates in rule2 and rule3 are combined by hoisting\r
- to create a prediction expression for rule1 the result is:\r
-\r
- if ( LA(1)==ID\r
- && ( isX(LATEXT(1) || !isX(LATEXT(1) ) ) { rule1(); ...\r
-\r
- This is inefficient, but more importantly, can lead to false\r
- assumptions that the predicate expression distinguishes the rule1\r
- alternative with some other alternative with lookahead ID. In\r
- MR11 one can write:\r
-\r
- #pred IsX <<isX(LATEXT(1))>>?\r
-\r
- ...\r
-\r
- rule2: <<IsX>>? ID ;\r
- rule3: <<!IsX>>? ID ;\r
-\r
- During hoisting MR11 recognizes this as a special case and\r
- eliminates the predicates. The result is a prediction\r
- expression like the following:\r
-\r
- if ( LA(1)==ID ) { rule1(); ...\r
-\r
- Please note that the following cases which appear to be equivalent\r
- *cannot* be simplified by MR11 during hoisting because the hoisting\r
- logic only checks for a "!" in the predicate action, not in the\r
- predicate expression for a predicate symbol.\r
-\r
- *Not* equivalent and is not simplified during hoisting:\r
-\r
- #pred IsX <<isX(LATEXT(1))>>?\r
- #pred NotX <<!isX(LATEXT(1))>>?\r
- ...\r
- rule2: <<IsX>>? ID ;\r
- rule3: <<NotX>>? ID ;\r
-\r
- *Not* equivalent and is not simplified during hoisting:\r
-\r
- #pred IsX <<isX(LATEXT(1))>>?\r
- #pred NotX !IsX\r
- ...\r
- rule2: <<IsX>>? ID ;\r
- rule3: <<NotX>>? ID ;\r
-\r
- Now we will discuss goal (b).\r
-\r
- When antlr discovers that there is a lookahead ambiguity between\r
- two alternatives it attempts to resolve the ambiguity by searching\r
- for predicates in both alternatives. In the past any predicate\r
- would do, even if the same one appeared in both alternatives:\r
-\r
- rule: <<p(LATEXT(1))>>? X\r
- | <<p(LATEXT(1))>>? X\r
- ;\r
-\r
- The #pred statement is a start towards solving this problem.\r
- During ambiguity resolution (*not* predicate hoisting) the\r
- predicates for the two alternatives are expanded and compared.\r
- Consider the following example:\r
-\r
- #pred Upper <<isUpper(LATEXT(1))>>?\r
- #pred Lower <<isLower(LATEXT(1))>>?\r
- #pred Alpha <<isAlpha(LATEXT(1))>>? Upper || Lower\r
-\r
- rule0: rule1\r
- | <<Alpha>>? ID\r
- ;\r
-\r
- rule1:\r
- | rule2\r
- | rule3\r
- ...\r
- ;\r
-\r
- rule2: <<Upper>>? ID;\r
- rule3: <<Lower>>? ID;\r
-\r
- The definition of #pred Alpha expresses:\r
-\r
- a. to test the predicate use the C code "isAlpha(LATEXT(1))"\r
-\r
- b. to analyze the predicate use the information that\r
- Alpha is equivalent to the union of Upper and Lower,\r
-\r
- During ambiguity resolution the definition of Alpha is expanded\r
- into "Upper || Lower" and compared with the predicate in the other\r
- alternative, which is also "Upper || Lower". Because they are\r
- identical MR11 will report a problem.\r
-\r
- -------------------------------------------------------------------------\r
- t10.g, line 5: warning: the predicates used to disambiguate rule rule0\r
- (file t10.g alt 1 line 5 and alt 2 line 6)\r
- are identical when compared without context and may have no\r
- resolving power for some lookahead sequences.\r
- -------------------------------------------------------------------------\r
-\r
- If you use the "-info p" option the output file will contain:\r
-\r
- +----------------------------------------------------------------------+\r
- |#if 0 |\r
- | |\r
- |The following predicates are identical when compared without |\r
- | lookahead context information. For some ambiguous lookahead |\r
- | sequences they may not have any power to resolve the ambiguity. |\r
- | |\r
- |Choice 1: rule0/1 alt 1 line 5 file t10.g |\r
- | |\r
- | The original predicate for choice 1 with available context |\r
- | information: |\r
- | |\r
- | OR expr |\r
- | |\r
- | pred << Upper>>? |\r
- | depth=k=1 rule rule2 line 14 t10.g |\r
- | set context: |\r
- | ID |\r
- | |\r
- | pred << Lower>>? |\r
- | depth=k=1 rule rule3 line 15 t10.g |\r
- | set context: |\r
- | ID |\r
- | |\r
- | The predicate for choice 1 after expansion (but without context |\r
- | information): |\r
- | |\r
- | OR expr |\r
- | |\r
- | pred << isUpper(LATEXT(1))>>? |\r
- | depth=k=1 rule line 1 t10.g |\r
- | |\r
- | pred << isLower(LATEXT(1))>>? |\r
- | depth=k=1 rule line 2 t10.g |\r
- | |\r
- | |\r
- |Choice 2: rule0/2 alt 2 line 6 file t10.g |\r
- | |\r
- | The original predicate for choice 2 with available context |\r
- | information: |\r
- | |\r
- | pred << Alpha>>? |\r
- | depth=k=1 rule rule0 line 6 t10.g |\r
- | set context: |\r
- | ID |\r
- | |\r
- | The predicate for choice 2 after expansion (but without context |\r
- | information): |\r
- | |\r
- | OR expr |\r
- | |\r
- | pred << isUpper(LATEXT(1))>>? |\r
- | depth=k=1 rule line 1 t10.g |\r
- | |\r
- | pred << isLower(LATEXT(1))>>? |\r
- | depth=k=1 rule line 2 t10.g |\r
- | |\r
- | |\r
- |#endif |\r
- +----------------------------------------------------------------------+\r
-\r
- The comparison of the predicates for the two alternatives takes\r
- place without context information, which means that in some cases\r
- the predicates will be considered identical even though they operate\r
- on disjoint lookahead sets. Consider:\r
-\r
- #pred Alpha\r
-\r
- rule1: <<Alpha>>? ID\r
- | <<Alpha>>? Label\r
- ;\r
-\r
- Because the comparison of predicates takes place without context\r
- these will be considered identical. The reason for comparing\r
- without context is that otherwise it would be necessary to re-evaluate\r
- the entire predicate expression for each possible lookahead sequence.\r
- This would require more code to be written and more CPU time during\r
- grammar analysis, and it is not yet clear whether anyone will even make\r
- use of the new #pred facility.\r
-\r
- A temporary workaround might be to use different #pred statements\r
- for predicates you know have different context. This would avoid\r
- extraneous warnings.\r
-\r
- The above example might be termed a "false positive". Comparison\r
- without context will also lead to "false negatives". Consider the\r
- following example:\r
-\r
- #pred Alpha\r
- #pred Beta\r
-\r
- rule1: <<Alpha>>? A\r
- | rule2\r
- ;\r
-\r
- rule2: <<Alpha>>? A\r
- | <<Beta>>? B\r
- ;\r
-\r
- The predicate used for alt 2 of rule1 is (Alpha || Beta). This\r
- appears to be different than the predicate Alpha used for alt1.\r
- However, the context of Beta is B. Thus when the lookahead is A\r
- Beta will have no resolving power and Alpha will be used for both\r
- alternatives. Using the same predicate for both alternatives isn't\r
- very helpful, but this will not be detected with 1.33MR11.\r
-\r
- To properly handle this the predicate expression would have to be\r
- evaluated for each distinct lookahead context.\r
-\r
- To determine whether two predicate expressions are identical is\r
- difficult. The routine may fail to identify identical predicates.\r
-\r
- The #pred feature also compares predicates to see if a choice between\r
- alternatives which is resolved by a predicate which makes the second\r
- choice unreachable. Consider the following example:\r
-\r
- #pred A <<A(LATEXT(1)>>?\r
- #pred B <<B(LATEXT(1)>>?\r
- #pred A_or_B A || B\r
-\r
- r : s\r
- | t\r
- ;\r
- s : <<A_or_B>>? ID\r
- ;\r
- t : <<A>>? ID\r
- ;\r
-\r
- ----------------------------------------------------------------------------\r
- t11.g, line 5: warning: the predicate used to disambiguate the\r
- first choice of rule r\r
- (file t11.g alt 1 line 5 and alt 2 line 6)\r
- appears to "cover" the second predicate when compared without context.\r
- The second predicate may have no resolving power for some lookahead\r
- sequences.\r
- ----------------------------------------------------------------------------\r
-\r
-#139. (Changed in MR11) Problem with -gp in C++ mode\r
-\r
- The -gp option to add a prefix to rule names did not work in\r
- C++ mode. This has been fixed.\r
-\r
- Reported by Alexey Demakov (demakov@kazbek.ispras.ru).\r
-\r
-#138. (Changed in MR11) Additional makefiles for non-MSVC++ MS systems\r
-\r
- Sramji Ramanathan (ps@kumaran.com) has supplied makefiles for\r
- building antlr and dlg with Win95/NT development tools that\r
- are not based on MSVC5. They are pccts/antlr/AntlrMS.mak and\r
- pccts/dlg/DlgMS.mak.\r
-\r
- The first line of the makefiles require a definition of PCCTS_HOME.\r
-\r
- These are in additiion to the AntlrMSVC50.* and DlgMSVC50.*\r
- supplied by Jeff Vincent (JVincent@novell.com).\r
-\r
-#137. (Changed in MR11) Token getType(), getText(), getLine() const members\r
-\r
- --------------------------------------------------------------------\r
- If you use ANTLRCommonToken this change probably does not affect you.\r
- --------------------------------------------------------------------\r
-\r
- For a long time it has bothered me that these accessor functions\r
- in ANTLRAbstractToken were not const member functions. I have\r
- refrained from changing them because it require users to modify\r
- existing token class definitions which are derived directly\r
- from ANTLRAbstractToken. I think it is now time.\r
-\r
- For those who are not used to C++, a "const member function" is a\r
- member function which does not modify its own object - the thing\r
- to which "this" points. This is quite different from a function\r
- which does not modify its arguments\r
-\r
- Most token definitions based on ANTLRAbstractToken have something like\r
- the following in order to create concrete definitions of the pure\r
- virtual methods in ANTLRAbstractToken:\r
-\r
- class MyToken : public ANTLRAbstractToken {\r
- ...\r
- ANTLRTokenType getType() {return _type; }\r
- int getLine() {return _line; }\r
- ANTLRChar * getText() {return _text; }\r
- ...\r
- }\r
-\r
- The required change is simply to put "const" following the function\r
- prototype in the header (.h file) and the definition file (.cpp if\r
- it is not inline):\r
-\r
- class MyToken : public ANTLRAbstractToken {\r
- ...\r
- ANTLRTokenType getType() const {return _type; }\r
- int getLine() const {return _line; }\r
- ANTLRChar * getText() const {return _text; }\r
- ...\r
- }\r
-\r
- This was originally proposed a long time ago by Bruce\r
- Guenter (bruceg@qcc.sk.ca).\r
-\r
-#136. (Changed in MR11) Added getLength() to ANTLRCommonToken\r
-\r
- Classes ANTLRCommonToken and ANTLRCommonTokenNoRefCountToken\r
- now have a member function:\r
-\r
- int getLength() const { return strlen(getText()) }\r
-\r
- Suggested by Sramji Ramanathan (ps@kumaran.com).\r
-\r
-#135. (Changed in MR11) Raised antlr's own default ZZLEXBUFSIZE to 8k\r
-\r
-#134a. (ansi_mr10.zip) T.J. Parr's ANSI C grammar made 1.33MR11 compatible\r
-\r
- There is a typographical error in the definition of BITWISEOREQ:\r
-\r
- #token BITWISEOREQ "!=" should be "\|="\r
-\r
- When this change is combined with the bugfix to the follow set cache\r
- problem (Item #147) and a minor rearrangement of the grammar\r
- (Item #134b) it becomes a k=1 ck=2 grammar.\r
-\r
-#134b. (ansi_mr10.zip) T.J. Parr's ANSI C grammar made 1.33MR11 compatible\r
-\r
- The following changes were made in the ansi.g grammar (along with\r
- using -mrhoist on):\r
-\r
- ansi.g\r
- ======\r
- void tracein(char *) ====> void tracein(const char *)\r
- void traceout(char *) ====> void traceout(const char *)\r
-\r
- <LT(1)->getType()==IDENTIFIER ? isTypeName(LT(1)->getText()) : 1>>?\r
- ====> <<isTypeName(LT(1)->getText())>>?\r
-\r
- <<(LT(1)->getType()==LPARENTHESIS && LT(2)->getType()==IDENTIFIER) ? \\r
- isTypeName(LT(2)->getText()) : 1>>?\r
- ====> (LPARENTHESIS IDENTIFIER)? => <<isTypeName(LT(2)->getText())>>?\r
-\r
- <<(LT(1)->getType()==LPARENTHESIS && LT(2)->getType()==IDENTIFIER) ? \\r
- isTypeName(LT(2)->getText()) : 1>>?\r
- ====> (LPARENTHESIS IDENTIFIER)? => <<isTypeName(LT(2)->getText())>>?\r
-\r
- added to init(): traceOptionValueDefault=0;\r
- added to init(): traceOption(-1);\r
-\r
- change rule "statement":\r
-\r
- statement\r
- : plain_label_statement\r
- | case_label_statement\r
- | <<;>> expression SEMICOLON\r
- | compound_statement\r
- | selection_statement\r
- | iteration_statement\r
- | jump_statement\r
- | SEMICOLON\r
- ;\r
-\r
- plain_label_statement\r
- : IDENTIFIER COLON statement\r
- ;\r
-\r
- case_label_statement\r
- : CASE constant_expression COLON statement\r
- | DEFAULT COLON statement\r
- ;\r
-\r
- support.cpp\r
- ===========\r
- void tracein(char *) ====> void tracein(const char *)\r
- void traceout(char *) ====> void traceout(const char *)\r
-\r
- added to tracein(): ANTLRParser::tracein(r); // call superclass method\r
- added to traceout(): ANTLRParser::traceout(r); // call superclass method\r
-\r
- Makefile\r
- ========\r
- added to AFLAGS: -mrhoist on -prc on\r
-\r
-#133. (Changed in 1.33MR11) Make trace options public in ANTLRParser\r
-\r
- In checking T.J. Parr's ANSI C grammar for compatibility with\r
- 1.33MR11 discovered that it was inconvenient to have the\r
- trace facilities with protected access.\r
-\r
-#132. (Changed in 1.33MR11) Recognition of identical predicates in alts\r
-\r
- Prior to 1.33MR11, there would be no ambiguity warning when the\r
- very same predicate was used to disambiguate both alternatives:\r
-\r
- test: ref B\r
- | ref C\r
- ;\r
-\r
- ref : <<pred(LATEXT(1)>>? A\r
-\r
- In 1.33MR11 this will cause the warning:\r
-\r
- warning: the predicates used to disambiguate rule test\r
- (file v98.g alt 1 line 1 and alt 2 line 2)\r
- are identical and have no resolving power\r
-\r
- ----------------- Note -----------------\r
-\r
- This is different than the following case\r
-\r
- test: <<pred(LATEXT(1))>>? A B\r
- | <<pred(LATEXT(1)>>? A C\r
- ;\r
-\r
- In this case there are two distinct predicates\r
- which have exactly the same text. In the first\r
- example there are two references to the same\r
- predicate. The problem represented by this\r
- grammar will be addressed later.\r
-\r
-#131. (Changed in 1.33MR11) Case insensitive command line options\r
-\r
- Command line switches like "-CC" and keywords like "on", "off",\r
- and "stdin" are no longer case sensitive in antlr, dlg, and sorcerer.\r
-\r
-#130. (Changed in 1.33MR11) Changed ANTLR_VERSION to int from string\r
-\r
- The ANTLR_VERSION was not an integer, making it difficult to\r
- perform conditional compilation based on the antlr version.\r
-\r
- Henceforth, ANTLR_VERSION will be:\r
-\r
- (base_version * 10000) + release number\r
-\r
- thus 1.33MR11 will be: 133*100+11 = 13311\r
-\r
- Suggested by Rainer Janssen (Rainer.Janssen@Informatik.Uni-Oldenburg.DE).\r
-\r
-#129. (Changed in 1.33MR11) Addition of ANTLR_VERSION to <parserName>.h\r
-\r
- The following code is now inserted into <parserName>.h amd\r
- stdpccts.h:\r
-\r
- #ifndef ANTLR_VERSION\r
- #define ANTLR_VERSION 13311\r
- #endif\r
-\r
- Suggested by Rainer Janssen (Rainer.Janssen@Informatik.Uni-Oldenburg.DE)\r
-\r
-#128. (Changed in 1.33MR11) Redundant predicate code in (<<pred>>? ...)+\r
-\r
- Prior to 1.33MR11, the following grammar would generate\r
- redundant tests for the "while" condition.\r
-\r
- rule2 : (<<pred>>? X)+ X\r
- | B\r
- ;\r
-\r
- The code would resemble:\r
-\r
- if (LA(1)==X) {\r
- if (pred) {\r
- do {\r
- if (!pred) {zzfailed_pred(" pred");}\r
- zzmatch(X); zzCONSUME;\r
- } while (LA(1)==X && pred && pred);\r
- } else {...\r
-\r
- With 1.33MR11 the redundant predicate test is omitted.\r
-\r
-#127. (Changed in 1.33MR11)\r
-\r
- Count Syntax Errors Count DLG Errors\r
- ------------------- ----------------\r
-\r
- C++ mode ANTLRParser:: DLGLexerBase::\r
- syntaxErrCount lexErrCount\r
- C mode zzSyntaxErrCount zzLexErrCount\r
-\r
- The C mode variables are global and initialized to 0.\r
- They are *not* reset to 0 automatically when antlr is\r
- restarted.\r
-\r
- The C++ mode variables are public. They are initialized\r
- to 0 by the constructors. They are *not* reset to 0 by the\r
- ANTLRParser::init() method.\r
-\r
- Suggested by Reinier van den Born (reinier@vnet.ibm.com).\r
-\r
-#126. (Changed in 1.33MR11) Addition of #first <<...>>\r
-\r
- The #first <<...>> inserts the specified text in the output\r
- files before any other #include statements required by pccts.\r
- The only things before the #first text are comments and\r
- a #define ANTLR_VERSION.\r
-\r
- Requested by and Esa Pulkkinen (esap@cs.tut.fi) and Alexin\r
- Zoltan (alexin@inf.u-szeged.hu).\r
-\r
-#125. (Changed in 1.33MR11) Lookahead for (guard)? && <<p>>? predicates\r
-\r
- When implementing the new style of guard predicate (Item #113)\r
- in 1.33MR10 I decided to temporarily ignore the problem of\r
- computing the "narrowest" lookahead context.\r
-\r
- Consider the following k=1 grammar:\r
-\r
- start : a\r
- | b\r
- ;\r
-\r
- a : (A)? && <<pred1(LATEXT(1))>>? ab ;\r
- b : (B)? && <<pred2(LATEXT(1))>>? ab ;\r
-\r
- ab : A | B ;\r
-\r
- In MR10 the context for both "a" and "b" was {A B} because this is\r
- the first set of rule "ab". Normally, this is not a problem because\r
- the predicate which follows the guard inhibits any ambiguity report\r
- by antlr.\r
-\r
- In MR11 the first set for rule "a" is {A} and for rule "b" it is {B}.\r
-\r
-#124. A Note on the New "&&" Style Guarded Predicates\r
-\r
- I've been asked several times, "What is the difference between\r
- the old "=>" style guard predicates and the new style "&&" guard\r
- predicates, and how do you choose one over the other" ?\r
-\r
- The main difference is that the "=>" does not apply the\r
- predicate if the context guard doesn't match, whereas\r
- the && form always does. What is the significance ?\r
-\r
- If you have a predicate which is not on the "leading edge"\r
- it is cannot be hoisted. Suppose you need a predicate that\r
- looks at LA(2). You must introduce it manually. The\r
- classic example is:\r
-\r
- castExpr :\r
- LP typeName RP\r
- | ....\r
- ;\r
-\r
- typeName : <<isTypeName(LATEXT(1))>>? ID\r
- | STRUCT ID\r
- ;\r
-\r
- The problem is that isTypeName() isn't on the leading edge\r
- of typeName, so it won't be hoisted into castExpr to help\r
- make a decision on which production to choose.\r
-\r
- The *first* attempt to fix it is this:\r
-\r
- castExpr :\r
- <<isTypeName(LATEXT(2))>>?\r
- LP typeName RP\r
- | ....\r
- ;\r
-\r
- Unfortunately, this won't work because it ignores\r
- the problem of STRUCT. The solution is to apply\r
- isTypeName() in castExpr if LA(2) is an ID and\r
- don't apply it when LA(2) is STRUCT:\r
-\r
- castExpr :\r
- (LP ID)? => <<isTypeName(LATEXT(2))>>?\r
- LP typeName RP\r
- | ....\r
- ;\r
-\r
- In conclusion, the "=>" style guarded predicate is\r
- useful when:\r
-\r
- a. the tokens required for the predicate\r
- are not on the leading edge\r
- b. there are alternatives in the expression\r
- selected by the predicate for which the\r
- predicate is inappropriate\r
-\r
- If (b) were false, then one could use a simple\r
- predicate (assuming "-prc on"):\r
-\r
- castExpr :\r
- <<isTypeName(LATEXT(2))>>?\r
- LP typeName RP\r
- | ....\r
- ;\r
-\r
- typeName : <<isTypeName(LATEXT(1))>>? ID\r
- ;\r
-\r
- So, when do you use the "&&" style guarded predicate ?\r
-\r
- The new-style "&&" predicate should always be used with\r
- predicate context. The context guard is in ADDITION to\r
- the automatically computed context. Thus it useful for\r
- predicates which depend on the token type for reasons\r
- other than context.\r
-\r
- The following example is contributed by Reinier van den Born\r
- (reinier@vnet.ibm.com).\r
-\r
- +-------------------------------------------------------------------------+\r
- | This grammar has two ways to call functions: |\r
- | |\r
- | - a "standard" call syntax with parens and comma separated args |\r
- | - a shell command like syntax (no parens and spacing separated args) |\r
- | |\r
- | The former also allows a variable to hold the name of the function, |\r
- | the latter can also be used to call external commands. |\r
- | |\r
- | The grammar (simplified) looks like this: |\r
- | |\r
- | fun_call : ID "(" { expr ("," expr)* } ")" |\r
- | /* ID is function name */ |\r
- | | "@" ID "(" { expr ("," expr)* } ")" |\r
- | /* ID is var containing fun name */ |\r
- | ; |\r
- | |\r
- | command : ID expr* /* ID is function name */ |\r
- | | path expr* /* path is external command name */ |\r
- | ; |\r
- | |\r
- | path : ID /* left out slashes and such */ |\r
- | | "@" ID /* ID is environment var */ |\r
- | ; |\r
- | |\r
- | expr : .... |\r
- | | "(" expr ")"; |\r
- | |\r
- | call : fun_call |\r
- | | command |\r
- | ; |\r
- | |\r
- | Obviously the call is wildly ambiguous. This is more or less how this |\r
- | is to be resolved: |\r
- | |\r
- | A call begins with an ID or an @ followed by an ID. |\r
- | |\r
- | If it is an ID and if it is an ext. command name -> command |\r
- | if followed by a paren -> fun_call |\r
- | otherwise -> command |\r
- | |\r
- | If it is an @ and if the ID is a var name -> fun_call |\r
- | otherwise -> command |\r
- | |\r
- | One can implement these rules quite neatly using && predicates: |\r
- | |\r
- | call : ("@" ID)? && <<isVarName(LT(2))>>? fun_call |\r
- | | (ID)? && <<isExtCmdName>>? command |\r
- | | (ID "(")? fun_call |\r
- | | command |\r
- | ; |\r
- | |\r
- | This can be done better, so it is not an ideal example, but it |\r
- | conveys the principle. |\r
- +-------------------------------------------------------------------------+\r
-\r
-#123. (Changed in 1.33MR11) Correct definition of operators in ATokPtr.h\r
-\r
- The return value of operators in ANTLRTokenPtr:\r
-\r
- changed: unsigned ... operator !=(...)\r
- to: int ... operator != (...)\r
- changed: unsigned ... operator ==(...)\r
- to: int ... operator == (...)\r
-\r
- Suggested by R.A. Nelson (cowboy@VNET.IBM.COM)\r
-\r
-#122. (Changed in 1.33MR11) Member functions to reset DLG in C++ mode\r
-\r
- void DLGFileReset(FILE *f) { input = f; found_eof = 0; }\r
- void DLGStringReset(DLGChar *s) { input = s; p = &input[0]; }\r
-\r
- Supplied by R.A. Nelson (cowboy@VNET.IBM.COM)\r
-\r
-#121. (Changed in 1.33MR11) Another attempt to fix -o (output dir) option\r
-\r
- Another attempt is made to improve the -o option of antlr, dlg,\r
- and sorcerer. This one by JVincent (JVincent@novell.com).\r
-\r
- The current rule:\r
-\r
- a. If -o is not specified than any explicit directory\r
- names are retained.\r
-\r
- b. If -o is specified than the -o directory name overrides any\r
- explicit directory names.\r
-\r
- c. The directory name of the grammar file is *not* stripped\r
- to create the main output file. However it is stil subject\r
- to override by the -o directory name.\r
-\r
-#120. (Changed in 1.33MR11) "-info f" output to stdout rather than stderr\r
-\r
- Added option 0 (e.g. "-info 0") which is a noop.\r
-\r
-#119. (Changed in 1.33MR11) Ambiguity aid for grammars\r
-\r
- The user can ask for additional information on ambiguities reported\r
- by antlr to stdout. At the moment, only one ambiguity report can\r
- be created in an antlr run.\r
-\r
- This feature is enabled using the "-aa" (Ambiguity Aid) option.\r
-\r
- The following options control the reporting of ambiguities:\r
-\r
- -aa ruleName Selects reporting by name of rule\r
- -aa lineNumber Selects reporting by line number\r
- (file name not compared)\r
-\r
- -aam Selects "multiple" reporting for a token\r
- in the intersection set of the\r
- alternatives.\r
-\r
- For instance, the token ID may appear dozens\r
- of times in various paths as the program\r
- explores the rules which are reachable from\r
- the point of an ambiguity. With option -aam\r
- every possible path the search program\r
- encounters is reported.\r
-\r
- Without -aam only the first encounter is\r
- reported. This may result in incomplete\r
- information, but the information may be\r
- sufficient and much shorter.\r
-\r
- -aad depth Selects the depth of the search.\r
- The default value is 1.\r
-\r
- The number of paths to be searched, and the\r
- size of the report can grow geometrically\r
- with the -ck value if a full search for all\r
- contributions to the source of the ambiguity\r
- is explored.\r
-\r
- The depth represents the number of tokens\r
- in the lookahead set which are matched against\r
- the set of ambiguous tokens. A depth of 1\r
- means that the search stops when a lookahead\r
- sequence of just one token is matched.\r
-\r
- A k=1 ck=6 grammar might generate 5,000 items\r
- in a report if a full depth 6 search is made\r
- with the Ambiguity Aid. The source of the\r
- problem may be in the first token and obscured\r
- by the volume of data - I hesitate to call\r
- it information.\r
-\r
- When the user selects a depth > 1, the search\r
- is first performed at depth=1 for both\r
- alternatives, then depth=2 for both alternatives,\r
- etc.\r
-\r
- Sample output for rule grammar in antlr.g itself:\r
-\r
- +---------------------------------------------------------------------+\r
- | Ambiguity Aid |\r
- | |\r
- | Choice 1: grammar/70 line 632 file a.g |\r
- | Choice 2: grammar/82 line 644 file a.g |\r
- | |\r
- | Intersection of lookahead[1] sets: |\r
- | |\r
- | "\}" "class" "#errclass" "#tokclass" |\r
- | |\r
- | Choice:1 Depth:1 Group:1 ("#errclass") |\r
- | 1 in (...)* block grammar/70 line 632 a.g |\r
- | 2 to error grammar/73 line 635 a.g |\r
- | 3 error error/1 line 894 a.g |\r
- | 4 #token "#errclass" error/2 line 895 a.g |\r
- | |\r
- | Choice:1 Depth:1 Group:2 ("#tokclass") |\r
- | 2 to tclass grammar/74 line 636 a.g |\r
- | 3 tclass tclass/1 line 937 a.g |\r
- | 4 #token "#tokclass" tclass/2 line 938 a.g |\r
- | |\r
- | Choice:1 Depth:1 Group:3 ("class") |\r
- | 2 to class_def grammar/75 line 637 a.g |\r
- | 3 class_def class_def/1 line 669 a.g |\r
- | 4 #token "class" class_def/3 line 671 a.g |\r
- | |\r
- | Choice:1 Depth:1 Group:4 ("\}") |\r
- | 2 #token "\}" grammar/76 line 638 a.g |\r
- | |\r
- | Choice:2 Depth:1 Group:5 ("#errclass") |\r
- | 1 in (...)* block grammar/83 line 645 a.g |\r
- | 2 to error grammar/93 line 655 a.g |\r
- | 3 error error/1 line 894 a.g |\r
- | 4 #token "#errclass" error/2 line 895 a.g |\r
- | |\r
- | Choice:2 Depth:1 Group:6 ("#tokclass") |\r
- | 2 to tclass grammar/94 line 656 a.g |\r
- | 3 tclass tclass/1 line 937 a.g |\r
- | 4 #token "#tokclass" tclass/2 line 938 a.g |\r
- | |\r
- | Choice:2 Depth:1 Group:7 ("class") |\r
- | 2 to class_def grammar/95 line 657 a.g |\r
- | 3 class_def class_def/1 line 669 a.g |\r
- | 4 #token "class" class_def/3 line 671 a.g |\r
- | |\r
- | Choice:2 Depth:1 Group:8 ("\}") |\r
- | 2 #token "\}" grammar/96 line 658 a.g |\r
- +---------------------------------------------------------------------+\r
-\r
- For a linear lookahead set ambiguity (where k=1 or for k>1 but\r
- when all lookahead sets [i] with i<k all have degree one) the\r
- reports appear in the following order:\r
-\r
- for (depth=1 ; depth <= "-aad depth" ; depth++) {\r
- for (alternative=1; alternative <=2 ; alternative++) {\r
- while (matches-are-found) {\r
- group++;\r
- print-report\r
- };\r
- };\r
- };\r
-\r
- For reporting a k-tuple ambiguity, the reports appear in the\r
- following order:\r
-\r
- for (depth=1 ; depth <= "-aad depth" ; depth++) {\r
- while (matches-are-found) {\r
- for (alternative=1; alternative <=2 ; alternative++) {\r
- group++;\r
- print-report\r
- };\r
- };\r
- };\r
-\r
- This is because matches are generated in different ways for\r
- linear lookahead and k-tuples.\r
-\r
-#118. (Changed in 1.33MR11) DEC VMS makefile and VMS related changes\r
-\r
- Revised makefiles for DEC/VMS operating system for antlr, dlg,\r
- and sorcerer.\r
-\r
- Reduced names of routines with external linkage to less than 32\r
- characters to conform to DEC/VMS linker limitations.\r
-\r
- Jean-Francois Pieronne discovered problems with dlg and antlr\r
- due to the VMS linker not being case sensitive for names with\r
- external linkage. In dlg the problem was with "className" and\r
- "ClassName". In antlr the problem was with "GenExprSets" and\r
- "genExprSets".\r
-\r
- Added genmms, a version of genmk for the DEC/VMS version of make.\r
- The source is in directory pccts/support/DECmms.\r
-\r
- All VMS contributions by Jean-Francois Pieronne (jfp@iname.com).\r
-\r
-#117. (Changed in 1.33MR10) new EXPERIMENTAL predicate hoisting code\r
-\r
- The hoisting of predicates into rules to create prediction\r
- expressions is a problem in antlr. Consider the following\r
- example (k=1 with -prc on):\r
-\r
- start : (a)* "@" ;\r
- a : b | c ;\r
- b : <<isUpper(LATEXT(1))>>? A ;\r
- c : A ;\r
-\r
- Prior to 1.33MR10 the code generated for "start" would resemble:\r
-\r
- while {\r
- if (LA(1)==A &&\r
- (!LA(1)==A || isUpper())) {\r
- a();\r
- }\r
- };\r
-\r
- This code is wrong because it makes rule "c" unreachable from\r
- "start". The essence of the problem is that antlr fails to\r
- recognize that there can be a valid alternative within "a" even\r
- when the predicate <<isUpper(LATEXT(1))>>? is false.\r
-\r
- In 1.33MR10 with -mrhoist the hoisting of the predicate into\r
- "start" is suppressed because it recognizes that "c" can\r
- cover all the cases where the predicate is false:\r
-\r
- while {\r
- if (LA(1)==A) {\r
- a();\r
- }\r
- };\r
-\r
- With the antlr "-info p" switch the user will receive information\r
- about the predicate suppression in the generated file:\r
-\r
- --------------------------------------------------------------\r
- #if 0\r
-\r
- Hoisting of predicate suppressed by alternative without predicate.\r
- The alt without the predicate includes all cases where\r
- the predicate is false.\r
-\r
- WITH predicate: line 7 v1.g\r
- WITHOUT predicate: line 7 v1.g\r
-\r
- The context set for the predicate:\r
-\r
- A\r
-\r
- The lookahead set for the alt WITHOUT the semantic predicate:\r
-\r
- A\r
-\r
- The predicate:\r
-\r
- pred << isUpper(LATEXT(1))>>?\r
- depth=k=1 rule b line 9 v1.g\r
- set context:\r
- A\r
- tree context: null\r
-\r
- Chain of referenced rules:\r
-\r
- #0 in rule start (line 5 v1.g) to rule a\r
- #1 in rule a (line 7 v1.g)\r
-\r
- #endif\r
- --------------------------------------------------------------\r
-\r
- A predicate can be suppressed by a combination of alternatives\r
- which, taken together, cover a predicate:\r
-\r
- start : (a)* "@" ;\r
-\r
- a : b | ca | cb | cc ;\r
-\r
- b : <<isUpper(LATEXT(1))>>? ( A | B | C ) ;\r
-\r
- ca : A ;\r
- cb : B ;\r
- cc : C ;\r
-\r
- Consider a more complex example in which "c" covers only part of\r
- a predicate:\r
-\r
- start : (a)* "@" ;\r
-\r
- a : b\r
- | c\r
- ;\r
-\r
- b : <<isUpper(LATEXT(1))>>?\r
- ( A\r
- | X\r
- );\r
-\r
- c : A\r
- ;\r
-\r
- Prior to 1.33MR10 the code generated for "start" would resemble:\r
-\r
- while {\r
- if ( (LA(1)==A || LA(1)==X) &&\r
- (! (LA(1)==A || LA(1)==X) || isUpper()) {\r
- a();\r
- }\r
- };\r
-\r
- With 1.33MR10 and -mrhoist the predicate context is restricted to\r
- the non-covered lookahead. The code resembles:\r
-\r
- while {\r
- if ( (LA(1)==A || LA(1)==X) &&\r
- (! (LA(1)==X) || isUpper()) {\r
- a();\r
- }\r
- };\r
-\r
- With the antlr "-info p" switch the user will receive information\r
- about the predicate restriction in the generated file:\r
-\r
- --------------------------------------------------------------\r
- #if 0\r
-\r
- Restricting the context of a predicate because of overlap\r
- in the lookahead set between the alternative with the\r
- semantic predicate and one without\r
- Without this restriction the alternative without the predicate\r
- could not be reached when input matched the context of the\r
- predicate and the predicate was false.\r
-\r
- WITH predicate: line 11 v4.g\r
- WITHOUT predicate: line 12 v4.g\r
-\r
- The original context set for the predicate:\r
-\r
- A X\r
-\r
- The lookahead set for the alt WITHOUT the semantic predicate:\r
-\r
- A\r
-\r
- The intersection of the two sets\r
-\r
- A\r
-\r
- The original predicate:\r
-\r
- pred << isUpper(LATEXT(1))>>?\r
- depth=k=1 rule b line 15 v4.g\r
- set context:\r
- A X\r
- tree context: null\r
-\r
- The new (modified) form of the predicate:\r
-\r
- pred << isUpper(LATEXT(1))>>?\r
- depth=k=1 rule b line 15 v4.g\r
- set context:\r
- X\r
- tree context: null\r
-\r
- #endif\r
- --------------------------------------------------------------\r
-\r
- The bad news about -mrhoist:\r
-\r
- (a) -mrhoist does not analyze predicates with lookahead\r
- depth > 1.\r
-\r
- (b) -mrhoist does not look past a guarded predicate to\r
- find context which might cover other predicates.\r
-\r
- For these cases you might want to use syntactic predicates.\r
- When a semantic predicate fails during guess mode the guess\r
- fails and the next alternative is tried.\r
-\r
- Limitation (a) is illustrated by the following example:\r
-\r
- start : (stmt)* EOF ;\r
-\r
- stmt : cast\r
- | expr\r
- ;\r
- cast : <<isTypename(LATEXT(2))>>? LP ID RP ;\r
-\r
- expr : LP ID RP ;\r
-\r
- This is not much different from the first example, except that\r
- it requires two tokens of lookahead context to determine what\r
- to do. This predicate is NOT suppressed because the current version\r
- is unable to handle predicates with depth > 1.\r
-\r
- A predicate can be combined with other predicates during hoisting.\r
- In those cases the depth=1 predicates are still handled. Thus,\r
- in the following example the isUpper() predicate will be suppressed\r
- by line #4 when hoisted from "bizarre" into "start", but will still\r
- be present in "bizarre" in order to predict "stmt".\r
-\r
- start : (bizarre)* EOF ; // #1\r
- // #2\r
- bizarre : stmt // #3\r
- | A // #4\r
- ;\r
-\r
- stmt : cast\r
- | expr\r
- ;\r
-\r
- cast : <<isTypename(LATEXT(2))>>? LP ID RP ;\r
-\r
- expr : LP ID RP ;\r
- | <<isUpper(LATEXT(1))>>? A\r
-\r
- Limitation (b) is illustrated by the following example of a\r
- context guarded predicate:\r
-\r
- rule : (A)? <<p>>? // #1\r
- (A // #2\r
- |B // #3\r
- ) // #4\r
- | <<q>> B // #5\r
- ;\r
-\r
- Recall that this means that when the lookahead is NOT A then\r
- the predicate "p" is ignored and it attempts to match "A|B".\r
- Ideally, the "B" at line #3 should suppress predicate "q".\r
- However, the current version does not attempt to look past\r
- the guard predicate to find context which might suppress other\r
- predicates.\r
-\r
- In some cases -mrhoist will lead to the reporting of ambiguities\r
- which were not visible before:\r
-\r
- start : (a)* "@";\r
- a : bc | d;\r
- bc : b | c ;\r
-\r
- b : <<isUpper(LATEXT(1))>>? A;\r
- c : A ;\r
-\r
- d : A ;\r
-\r
- In this case there is a true ambiguity in "a" between "bc" and "d"\r
- which can both match "A". Without -mrhoist the predicate in "b"\r
- is hoisted into "a" and there is no ambiguity reported. However,\r
- with -mrhoist, the predicate in "b" is suppressed by "c" (as it\r
- should be) making the ambiguity in "a" apparent.\r
-\r
- The motivations for these changes were hoisting problems reported\r
- by Reinier van den Born (reinier@vnet.ibm.com) and several others.\r
-\r
-#116. (Changed in 1.33MR10) C++ mode: tracein/traceout rule name is (const char *)\r
-\r
- The prototype for C++ mode routine tracein (and traceout) has changed from\r
- "char *" to "const char *".\r
-\r
-#115. (Changed in 1.33MR10) Using guess mode with exception handlers in C mode\r
-\r
- The definition of the C mode macros zzmatch_wsig and zzsetmatch_wsig\r
- neglected to consider guess mode. When control passed to the rule's\r
- parse exception handler the routine would exit without ever closing the\r
- guess block. This would lead to unpredictable behavior.\r
-\r
- In 1.33MR10 the behavior of exceptions in C mode and C++ mode should be\r
- identical.\r
-\r
-#114. (Changed in 1.33MR10) difference in [zz]resynch() between C and C++ modes\r
-\r
- There was a slight difference in the way C and C++ mode resynchronized\r
- following a parsing error. The C routine would sometimes skip an extra\r
- token before attempting to resynchronize.\r
-\r
- The C routine was changed to match the C++ routine.\r
-\r
-#113. (Changed in 1.33MR10) new context guarded pred: (g)? && <<p>>? expr\r
-\r
- The existing context guarded predicate:\r
-\r
- rule : (guard)? => <<p>>? expr\r
- | next_alternative\r
- ;\r
-\r
- generates code which resembles:\r
-\r
- if (lookahead(expr) && (!guard || pred)) {\r
- expr()\r
- } else ....\r
-\r
- This is not suitable for some applications because it allows\r
- expr() to be invoked when the predicate is false. This is\r
- intentional because it is meant to mimic automatically computed\r
- predicate context.\r
-\r
- The new context guarded predicate uses the guard information\r
- differently because it has a different goal. Consider:\r
-\r
- rule : (guard)? && <<p>>? expr\r
- | next_alternative\r
- ;\r
-\r
- The new style of context guarded predicate is equivalent to:\r
-\r
- rule : <<guard==true && pred>>? expr\r
- | next_alternative\r
- ;\r
-\r
- It generates code which resembles:\r
-\r
- if (lookahead(expr) && guard && pred) {\r
- expr();\r
- } else ...\r
-\r
- Both forms of guarded predicates severely restrict the form of\r
- the context guard: it can contain no rule references, no\r
- (...)*, no (...)+, and no {...}. It may contain token and\r
- token class references, and alternation ("|").\r
-\r
- Addition for 1.33MR11: in the token expression all tokens must\r
- be at the same height of the token tree:\r
-\r
- (A ( B | C))? && ... is ok (all height 2)\r
- (A ( B | ))? && ... is not ok (some 1, some 2)\r
- (A B C D | E F G H)? && ... is ok (all height 4)\r
- (A B C D | E )? && ... is not ok (some 4, some 1)\r
-\r
- This restriction is required in order to properly compute the lookahead\r
- set for expressions like:\r
-\r
- rule1 : (A B C)? && <<pred>>? rule2 ;\r
- rule2 : (A|X) (B|Y) (C|Z);\r
-\r
- This addition was suggested by Rienier van den Born (reinier@vnet.ibm.com)\r
-\r
-#112. (Changed in 1.33MR10) failed validation predicate in C guess mode\r
-\r
- John Lilley (jlilley@empathy.com) suggested that failed validation\r
- predicates abort a guess rather than reporting a failed error.\r
- This was installed in C++ mode (Item #4). Only now was it noticed\r
- that the fix was never installed for C mode.\r
-\r
-#111. (Changed in 1.33MR10) moved zzTRACEIN to before init action\r
-\r
- When the antlr -gd switch is present antlr generates calls to\r
- zzTRACEIN at the start of a rule and zzTRACEOUT at the exit\r
- from a rule. Prior to 1.33MR10 Tthe call to zzTRACEIN was\r
- after the init-action, which could cause confusion because the\r
- init-actions were reported with the name of the enclosing rule,\r
- rather than the active rule.\r
-\r
-#110. (Changed in 1.33MR10) antlr command line copied to generated file\r
-\r
- The antlr command line is now copied to the generated file near\r
- the start.\r
-\r
-#109. (Changed in 1.33MR10) improved trace information\r
-\r
- The quality of the trace information provided by the "-gd"\r
- switch has been improved significantly. Here is an example\r
- of the output from a test program. It shows the rule name,\r
- the first token of lookahead, the call depth, and the guess\r
- status:\r
-\r
- exit rule gusxx {"?"} depth 2\r
- enter rule gusxx {"?"} depth 2\r
- enter rule gus1 {"o"} depth 3 guessing\r
- guess done - returning to rule gus1 {"o"} at depth 3\r
- (guess mode continues - an enclosing guess is still active)\r
- guess done - returning to rule gus1 {"Z"} at depth 3\r
- (guess mode continues - an enclosing guess is still active)\r
- exit rule gus1 {"Z"} depth 3 guessing\r
- guess done - returning to rule gusxx {"o"} at depth 2 (guess mode ends)\r
- enter rule gus1 {"o"} depth 3\r
- guess done - returning to rule gus1 {"o"} at depth 3 (guess mode ends)\r
- guess done - returning to rule gus1 {"Z"} at depth 3 (guess mode ends)\r
- exit rule gus1 {"Z"} depth 3\r
- line 1: syntax error at "Z" missing SC\r
- ...\r
-\r
- Rule trace reporting is controlled by the value of the integer\r
- [zz]traceOptionValue: when it is positive tracing is enabled,\r
- otherwise it is disabled. Tracing during guess mode is controlled\r
- by the value of the integer [zz]traceGuessOptionValue. When\r
- it is positive AND [zz]traceOptionValue is positive rule trace\r
- is reported in guess mode.\r
-\r
- The values of [zz]traceOptionValue and [zz]traceGuessOptionValue\r
- can be adjusted by subroutine calls listed below.\r
-\r
- Depending on the presence or absence of the antlr -gd switch\r
- the variable [zz]traceOptionValueDefault is set to 0 or 1. When\r
- the parser is initialized or [zz]traceReset() is called the\r
- value of [zz]traceOptionValueDefault is copied to [zz]traceOptionValue.\r
- The value of [zz]traceGuessOptionValue is always initialzed to 1,\r
- but, as noted earlier, nothing will be reported unless\r
- [zz]traceOptionValue is also positive.\r
-\r
- When the parser state is saved/restored the value of the trace\r
- variables are also saved/restored. If a restore causes a change in\r
- reporting behavior from on to off or vice versa this will be reported.\r
-\r
- When the -gd option is selected, the macro "#define zzTRACE_RULES"\r
- is added to appropriate output files.\r
-\r
- C++ mode\r
- --------\r
- int traceOption(int delta)\r
- int traceGuessOption(int delta)\r
- void traceReset()\r
- int traceOptionValueDefault\r
-\r
- C mode\r
- --------\r
- int zzTraceOption(int delta)\r
- int zzTraceGuessOption(int delta)\r
- void zzTraceReset()\r
- int zzTraceOptionValueDefault\r
-\r
- The argument "delta" is added to the traceOptionValue. To\r
- turn on trace when inside a particular rule one:\r
-\r
- rule : <<traceOption(+1);>>\r
- (\r
- rest-of-rule\r
- )\r
- <<traceOption(-1);>>\r
- ; /* fail clause */ <<traceOption(-1);>>\r
-\r
- One can use the same idea to turn *off* tracing within a\r
- rule by using a delta of (-1).\r
-\r
- An improvement in the rule trace was suggested by Sramji\r
- Ramanathan (ps@kumaran.com).\r
-\r
-#108. A Note on Deallocation of Variables Allocated in Guess Mode\r
-\r
- NOTE\r
- ------------------------------------------------------\r
- This mechanism only works for heap allocated variables\r
- ------------------------------------------------------\r
-\r
- The rewrite of the trace provides the machinery necessary\r
- to properly free variables or undo actions following a\r
- failed guess.\r
-\r
- The macro zzUSER_GUESS_HOOK(guessSeq,zzrv) is expanded\r
- as part of the zzGUESS macro. When a guess is opened\r
- the value of zzrv is 0. When a longjmp() is executed to\r
- undo the guess, the value of zzrv will be 1.\r
-\r
- The macro zzUSER_GUESS_DONE_HOOK(guessSeq) is expanded\r
- as part of the zzGUESS_DONE macro. This is executed\r
- whether the guess succeeds or fails as part of closing\r
- the guess.\r
-\r
- The guessSeq is a sequence number which is assigned to each\r
- guess and is incremented by 1 for each guess which becomes\r
- active. It is needed by the user to associate the start of\r
- a guess with the failure and/or completion (closing) of a\r
- guess.\r
-\r
- Guesses are nested. They must be closed in the reverse\r
- of the order that they are opened.\r
-\r
- In order to free memory used by a variable during a guess\r
- a user must write a routine which can be called to\r
- register the variable along with the current guess sequence\r
- number provided by the zzUSER_GUESS_HOOK macro. If the guess\r
- fails, all variables tagged with the corresponding guess\r
- sequence number should be released. This is ugly, but\r
- it would require a major rewrite of antlr 1.33 to use\r
- some mechanism other than setjmp()/longjmp().\r
-\r
- The order of calls for a *successful* guess would be:\r
-\r
- zzUSER_GUESS_HOOK(guessSeq,0);\r
- zzUSER_GUESS_DONE_HOOK(guessSeq);\r
-\r
- The order of calls for a *failed* guess would be:\r
-\r
- zzUSER_GUESS_HOOK(guessSeq,0);\r
- zzUSER_GUESS_HOOK(guessSeq,1);\r
- zzUSER_GUESS_DONE_HOOK(guessSeq);\r
-\r
- The default definitions of these macros are empty strings.\r
-\r
- Here is an example in C++ mode. The zzUSER_GUESS_HOOK and\r
- zzUSER_GUESS_DONE_HOOK macros and myGuessHook() routine\r
- can be used without change in both C and C++ versions.\r
-\r
- ----------------------------------------------------------------------\r
- <<\r
-\r
- #include "AToken.h"\r
-\r
- typedef ANTLRCommonToken ANTLRToken;\r
-\r
- #include "DLGLexer.h"\r
-\r
- int main() {\r
-\r
- {\r
- DLGFileInput in(stdin);\r
- DLGLexer lexer(&in,2000);\r
- ANTLRTokenBuffer pipe(&lexer,1);\r
- ANTLRCommonToken aToken;\r
- P parser(&pipe);\r
-\r
- lexer.setToken(&aToken);\r
- parser.init();\r
- parser.start();\r
- };\r
-\r
- fclose(stdin);\r
- fclose(stdout);\r
- return 0;\r
- }\r
-\r
- >>\r
-\r
- <<\r
- char *s=NULL;\r
-\r
- #undef zzUSER_GUESS_HOOK\r
- #define zzUSER_GUESS_HOOK(guessSeq,zzrv) myGuessHook(guessSeq,zzrv);\r
- #undef zzUSER_GUESS_DONE_HOOK\r
- #define zzUSER_GUESS_DONE_HOOK(guessSeq) myGuessHook(guessSeq,2);\r
-\r
- void myGuessHook(int guessSeq,int zzrv) {\r
- if (zzrv == 0) {\r
- fprintf(stderr,"User hook: starting guess #%d\n",guessSeq);\r
- } else if (zzrv == 1) {\r
- free (s);\r
- s=NULL;\r
- fprintf(stderr,"User hook: failed guess #%d\n",guessSeq);\r
- } else if (zzrv == 2) {\r
- free (s);\r
- s=NULL;\r
- fprintf(stderr,"User hook: ending guess #%d\n",guessSeq);\r
- };\r
- }\r
-\r
- >>\r
-\r
- #token A "a"\r
- #token "[\t \ \n]" <<skip();>>\r
-\r
- class P {\r
-\r
- start : (top)+\r
- ;\r
-\r
- top : (which) ? <<fprintf(stderr,"%s is a which\n",s); free(s); s=NULL; >>\r
- | other <<fprintf(stderr,"%s is an other\n",s); free(s); s=NULL; >>\r
- ; <<if (s != NULL) free(s); s=NULL; >>\r
-\r
- which : which2\r
- ;\r
-\r
- which2 : which3\r
- ;\r
- which3\r
- : (label)? <<fprintf(stderr,"%s is a label\n",s);>>\r
- | (global)? <<fprintf(stderr,"%s is a global\n",s);>>\r
- | (exclamation)? <<fprintf(stderr,"%s is an exclamation\n",s);>>\r
- ;\r
-\r
- label : <<s=strdup(LT(1)->getText());>> A ":" ;\r
-\r
- global : <<s=strdup(LT(1)->getText());>> A "::" ;\r
-\r
- exclamation : <<s=strdup(LT(1)->getText());>> A "!" ;\r
-\r
- other : <<s=strdup(LT(1)->getText());>> "other" ;\r
-\r
- }\r
- ----------------------------------------------------------------------\r
-\r
- This is a silly example, but illustrates the idea. For the input\r
- "a ::" with tracing enabled the output begins:\r
-\r
- ----------------------------------------------------------------------\r
- enter rule "start" depth 1\r
- enter rule "top" depth 2\r
- User hook: starting guess #1\r
- enter rule "which" depth 3 guessing\r
- enter rule "which2" depth 4 guessing\r
- enter rule "which3" depth 5 guessing\r
- User hook: starting guess #2\r
- enter rule "label" depth 6 guessing\r
- guess failed\r
- User hook: failed guess #2\r
- guess done - returning to rule "which3" at depth 5 (guess mode continues\r
- - an enclosing guess is still active)\r
- User hook: ending guess #2\r
- User hook: starting guess #3\r
- enter rule "global" depth 6 guessing\r
- exit rule "global" depth 6 guessing\r
- guess done - returning to rule "which3" at depth 5 (guess mode continues\r
- - an enclosing guess is still active)\r
- User hook: ending guess #3\r
- enter rule "global" depth 6 guessing\r
- exit rule "global" depth 6 guessing\r
- exit rule "which3" depth 5 guessing\r
- exit rule "which2" depth 4 guessing\r
- exit rule "which" depth 3 guessing\r
- guess done - returning to rule "top" at depth 2 (guess mode ends)\r
- User hook: ending guess #1\r
- enter rule "which" depth 3\r
- .....\r
- ----------------------------------------------------------------------\r
-\r
- Remember:\r
-\r
- (a) Only init-actions are executed during guess mode.\r
- (b) A rule can be invoked multiple times during guess mode.\r
- (c) If the guess succeeds the rule will be called once more\r
- without guess mode so that normal actions will be executed.\r
- This means that the init-action might need to distinguish\r
- between guess mode and non-guess mode using the variable\r
- [zz]guessing.\r
-\r
-#107. (Changed in 1.33MR10) construction of ASTs in guess mode\r
-\r
- Prior to 1.33MR10, when using automatic AST construction in C++\r
- mode for a rule, an AST would be constructed for elements of the\r
- rule even while in guess mode. In MR10 this no longer occurs.\r
-\r
-#106. (Changed in 1.33MR10) guess variable confusion\r
-\r
- In C++ mode a guess which failed always restored the parser state\r
- using zzGUESS_DONE as part of zzGUESS_FAIL. Prior to 1.33MR10,\r
- C mode required an explicit call to zzGUESS_DONE after the\r
- call to zzGUESS_FAIL.\r
-\r
- Consider:\r
-\r
- rule : (alpha)? beta\r
- | ...\r
- ;\r
-\r
- The generated code resembles:\r
-\r
- zzGUESS\r
- if (!zzrv && LA(1)==ID) { <==== line #1\r
- alpha\r
- zzGUESS_DONE\r
- beta\r
- } else {\r
- if (! zzrv) zzGUESS_DONE <==== line #2a\r
- ....\r
-\r
- However, in some cases line #2 was rendered:\r
-\r
- if (guessing) zzGUESS_DONE <==== line #2b\r
-\r
- This would work for simple test cases, but would fail in\r
- some cases where there was a guess while another guess was active.\r
- One kind of failure would be to match up the zzGUESS_DONE at line\r
- #2b with the "outer" guess which was still active. The outer\r
- guess would "succeed" when only the inner guess should have\r
- succeeded.\r
-\r
- In 1.33MR10 the behavior of zzGUESS and zzGUESS_FAIL in C and\r
- and C++ mode should be identical.\r
-\r
- The same problem appears in 1.33 vanilla in some places. For\r
- example:\r
-\r
- start : { (sub)? } ;\r
-\r
- or:\r
-\r
- start : (\r
- B\r
- | ( sub )?\r
- | C\r
- )+\r
- ;\r
-\r
- generates incorrect code.\r
-\r
- The general principle is:\r
-\r
- (a) use [zz]guessing only when deciding between a call to zzFAIL\r
- or zzGUESS_FAIL\r
-\r
- (b) use zzrv in all other cases\r
-\r
- This problem was discovered while testing changes to item #105.\r
- I believe this is now fixed. My apologies.\r
-\r
-#105. (Changed in 1.33MR10) guess block as single alt of (...)+\r
-\r
- Prior to 1.33MR10 the following constructs:\r
-\r
- rule_plus : (\r
- (sub)?\r
- )+\r
- ;\r
-\r
- rule_star : (\r
- (sub)?\r
- )*\r
- ;\r
-\r
- generated incorrect code for the guess block (which could result\r
- in runtime errors) because of an incorrect optimization of a\r
- block with only a single alternative.\r
-\r
- The fix caused some changes to the fix described in Item #49\r
- because there are now three code generation sequences for (...)+\r
- blocks containing a guess block:\r
-\r
- a. single alternative which is a guess block\r
- b. multiple alternatives in which the last is a guess block\r
- c. all other cases\r
-\r
- Forms like "rule_star" can have unexpected behavior when there\r
- is a syntax error: if the subrule "sub" is not matched *exactly*\r
- then "rule_star" will consume no tokens.\r
-\r
- Reported by Esa Pulkkinen (esap@cs.tut.fi).\r
-\r
-#104. (Changed in 1.33MR10) -o option for dlg\r
-\r
- There was problem with the code added by item #74 to handle the\r
- -o option of dlg. This should fix it.\r
-\r
-#103. (Changed in 1.33MR10) ANDed semantic predicates\r
-\r
- Rescinded.\r
-\r
- The optimization was a mistake.\r
- The resulting problem is described in Item #150.\r
-\r
-#102. (Changed in 1.33MR10) allow "class parser : .... {"\r
-\r
- The syntax of the class statement ("class parser-name {")\r
- has been extended to allow for the specification of base\r
- classes. An arbirtrary number of tokens may now appear\r
- between the class name and the "{". They are output\r
- again when the class declaration is generated. For\r
- example:\r
-\r
- class Parser : public MyBaseClassANTLRparser {\r
-\r
- This was suggested by a user, but I don't have a record\r
- of who it was.\r
-\r
-#101. (Changed in 1.33MR10) antlr -info command line switch\r
-\r
- -info\r
-\r
- p - extra predicate information in generated file\r
-\r
- t - information about tnode use:\r
- at the end of each rule in generated file\r
- summary on stderr at end of program\r
-\r
- m - monitor progress\r
- prints name of each rule as it is started\r
- flushes output at start of each rule\r
-\r
- f - first/follow set information to stdout\r
-\r
- 0 - no operation (added in 1.33MR11)\r
-\r
- The options may be combined and may appear in any order.\r
- For example:\r
-\r
- antlr -info ptm -CC -gt -mrhoist on mygrammar.g\r
-\r
-#100a. (Changed in 1.33MR10) Predicate tree simplification\r
-\r
- When the same predicates can be referenced in more than one\r
- alternative of a block large predicate trees can be formed.\r
-\r
- The difference that these optimizations make is so dramatic\r
- that I have decided to use it even when -mrhoist is not selected.\r
-\r
- Consider the following grammar:\r
-\r
- start : ( all )* ;\r
-\r
- all : a\r
- | d\r
- | e\r
- | f\r
- ;\r
-\r
- a : c A B\r
- | c A C\r
- ;\r
-\r
- c : <<AAA(LATEXT(2))>>?\r
- ;\r
-\r
- d : <<BBB(LATEXT(2))>>? B C\r
- ;\r
-\r
- e : <<CCC(LATEXT(2))>>? B C\r
- ;\r
-\r
- f : e X Y\r
- ;\r
-\r
- In rule "a" there is a reference to rule "c" in both alternatives.\r
- The length of the predicate AAA is k=2 and it can be followed in\r
- alternative 1 only by (A B) while in alternative 2 it can be\r
- followed only by (A C). Thus they do not have identical context.\r
-\r
- In rule "all" the alternatives which refer to rules "e" and "f" allow\r
- elimination of the duplicate reference to predicate CCC.\r
-\r
- The table below summarized the kind of simplification performed by\r
- 1.33MR10. In the table, X and Y stand for single predicates\r
- (not trees).\r
-\r
- (OR X (OR Y (OR Z))) => (OR X Y Z)\r
- (AND X (AND Y (AND Z))) => (AND X Y Z)\r
-\r
- (OR X (... (OR X Y) ... )) => (OR X (... Y ... ))\r
- (AND X (... (AND X Y) ... )) => (AND X (... Y ... ))\r
- (OR X (... (AND X Y) ... )) => (OR X (... ... ))\r
- (AND X (... (OR X Y) ... )) => (AND X (... ... ))\r
-\r
- (AND X) => X\r
- (OR X) => X\r
-\r
- In a test with a complex grammar for a real application, a predicate\r
- tree with six OR nodes and 12 leaves was reduced to "(OR X Y Z)".\r
-\r
- In 1.33MR10 there is a greater effort to release memory used\r
- by predicates once they are no longer in use.\r
-\r
-#100b. (Changed in 1.33MR10) Suppression of extra predicate tests\r
-\r
- The following optimizations require that -mrhoist be selected.\r
-\r
- It is relatively easy to optimize the code generated for predicate\r
- gates when they are of the form:\r
-\r
- (AND X Y Z ...)\r
- or (OR X Y Z ...)\r
-\r
- where X, Y, Z, and "..." represent individual predicates (leaves) not\r
- predicate trees.\r
-\r
- If the predicate is an AND the contexts of the X, Y, Z, etc. are\r
- ANDed together to create a single Tree context for the group and\r
- context tests for the individual predicates are suppressed:\r
-\r
- --------------------------------------------------\r
- Note: This was incorrect. The contexts should be\r
- ORed together. This has been fixed. A more \r
- complete description is available in item #152.\r
- ---------------------------------------------------\r
-\r
- Optimization 1: (AND X Y Z ...)\r
-\r
- Suppose the context for Xtest is LA(1)==LP and the context for\r
- Ytest is LA(1)==LP && LA(2)==ID.\r
-\r
- Without the optimization the code would resemble:\r
-\r
- if (lookaheadContext &&\r
- !(LA(1)==LP && LA(1)==LP && LA(2)==ID) ||\r
- ( (! LA(1)==LP || Xtest) &&\r
- (! (LA(1)==LP || LA(2)==ID) || Xtest)\r
- )) {...\r
-\r
- With the -mrhoist optimization the code would resemble:\r
-\r
- if (lookaheadContext &&\r
- ! (LA(1)==LP && LA(2)==ID) || (Xtest && Ytest) {...\r
-\r
- Optimization 2: (OR X Y Z ...) with identical contexts\r
-\r
- Suppose the context for Xtest is LA(1)==ID and for Ytest\r
- the context is also LA(1)==ID.\r
-\r
- Without the optimization the code would resemble:\r
-\r
- if (lookaheadContext &&\r
- ! (LA(1)==ID || LA(1)==ID) ||\r
- (LA(1)==ID && Xtest) ||\r
- (LA(1)==ID && Ytest) {...\r
-\r
- With the -mrhoist optimization the code would resemble:\r
-\r
- if (lookaheadContext &&\r
- (! LA(1)==ID) || (Xtest || Ytest) {...\r
-\r
- Optimization 3: (OR X Y Z ...) with distinct contexts\r
-\r
- Suppose the context for Xtest is LA(1)==ID and for Ytest\r
- the context is LA(1)==LP.\r
-\r
- Without the optimization the code would resemble:\r
-\r
- if (lookaheadContext &&\r
- ! (LA(1)==ID || LA(1)==LP) ||\r
- (LA(1)==ID && Xtest) ||\r
- (LA(1)==LP && Ytest) {...\r
-\r
- With the -mrhoist optimization the code would resemble:\r
-\r
- if (lookaheadContext &&\r
- (zzpf=0,\r
- (LA(1)==ID && (zzpf=1) && Xtest) ||\r
- (LA(1)==LP && (zzpf=1) && Ytest) ||\r
- !zzpf) {\r
-\r
- These may appear to be of similar complexity at first,\r
- but the non-optimized version contains two tests of each\r
- context while the optimized version contains only one\r
- such test, as well as eliminating some of the inverted\r
- logic (" !(...) || ").\r
-\r
- Optimization 4: Computation of predicate gate trees\r
-\r
- When generating code for the gates of predicate expressions\r
- antlr 1.33 vanilla uses a recursive procedure to generate\r
- "&&" and "||" expressions for testing the lookahead. As each\r
- layer of the predicate tree is exposed a new set of "&&" and\r
- "||" expressions on the lookahead are generated. In many\r
- cases the lookahead being tested has already been tested.\r
-\r
- With -mrhoist a lookahead tree is computed for the entire\r
- lookahead expression. This means that predicates with identical\r
- context or context which is a subset of another predicate's\r
- context disappear.\r
-\r
- This is especially important for predicates formed by rules\r
- like the following:\r
-\r
- uppperCaseVowel : <<isUpperCase(LATEXT(1))>>? vowel;\r
- vowel: : <<isVowel(LATEXT(1))>>? LETTERS;\r
-\r
- These predicates are combined using AND since both must be\r
- satisfied for rule upperCaseVowel. They have identical\r
- context which makes this optimization very effective.\r
-\r
- The affect of Items #100a and #100b together can be dramatic. In\r
- a very large (but real world) grammar one particular predicate\r
- expression was reduced from an (unreadable) 50 predicate leaves,\r
- 195 LA(1) terms, and 5500 characters to an (easily comprehensible)\r
- 3 predicate leaves (all different) and a *single* LA(1) term.\r
-\r
-#99. (Changed in 1.33MR10) Code generation for expression trees\r
-\r
- Expression trees are used for k>1 grammars and predicates with\r
- lookahead depth >1. This optimization must be enabled using\r
- "-mrhoist on". (Clarification added for 1.33MR11).\r
-\r
- In the processing of expression trees, antlr can generate long chains\r
- of token comparisons. Prior to 1.33MR10 there were many redundant\r
- parenthesis which caused problems for compilers which could handle\r
- expressions of only limited complexity. For example, to test an\r
- expression tree (root R A B C D), antlr would generate something\r
- resembling:\r
-\r
- (LA(1)==R && (LA(2)==A || (LA(2)==B || (LA(2)==C || LA(2)==D)))))\r
-\r
- If there were twenty tokens to test then there would be twenty\r
- parenthesis at the end of the expression.\r
-\r
- In 1.33MR10 the generated code for tree expressions resembles:\r
-\r
- (LA(1)==R && (LA(2)==A || LA(2)==B || LA(2)==C || LA(2)==D))\r
-\r
- For "complex" expressions the output is indented to reflect the LA\r
- number being tested:\r
-\r
- (LA(1)==R\r
- && (LA(2)==A || LA(2)==B || LA(2)==C || LA(2)==D\r
- || LA(2)==E || LA(2)==F)\r
- || LA(1)==S\r
- && (LA(2)==G || LA(2)==H))\r
-\r
-\r
- Suggested by S. Bochnak (S.Bochnak@@microTool.com.pl),\r
-\r
-#98. (Changed in 1.33MR10) Option "-info p"\r
-\r
- When the user selects option "-info p" the program will generate\r
- detailed information about predicates. If the user selects\r
- "-mrhoist on" additional detail will be provided explaining\r
- the promotion and suppression of predicates. The output is part\r
- of the generated file and sandwiched between #if 0/#endif statements.\r
-\r
- Consider the following k=1 grammar:\r
-\r
- start : ( all ) * ;\r
-\r
- all : ( a\r
- | b\r
- )\r
- ;\r
-\r
- a : c B\r
- ;\r
-\r
- c : <<LATEXT(1)>>?\r
- | B\r
- ;\r
-\r
- b : <<LATEXT(1)>>? X\r
- ;\r
-\r
- Below is an excerpt of the output for rule "start" for the three\r
- predicate options (off, on, and maintenance release style hoisting).\r
-\r
- For those who do not wish to use the "-mrhoist on" option for code\r
- generation the option can be used in a "diagnostic" mode to provide\r
- valuable information:\r
-\r
- a. where one should insert null actions to inhibit hoisting\r
- b. a chain of rule references which shows where predicates are\r
- being hoisted\r
-\r
- ======================================================================\r
- Example of "-info p" with "-mrhoist on"\r
- ======================================================================\r
- #if 0\r
-\r
- Hoisting of predicate suppressed by alternative without predicate.\r
- The alt without the predicate includes all cases where the\r
- predicate is false.\r
-\r
- WITH predicate: line 11 v36.g\r
- WITHOUT predicate: line 12 v36.g\r
-\r
- The context set for the predicate:\r
-\r
- B\r
-\r
- The lookahead set for alt WITHOUT the semantic predicate:\r
-\r
- B\r
-\r
- The predicate:\r
-\r
- pred << LATEXT(1)>>? depth=k=1 rule c line 11 v36.g\r
-\r
- set context:\r
- B\r
- tree context: null\r
-\r
- Chain of referenced rules:\r
-\r
- #0 in rule start (line 1 v36.g) to rule all\r
- #1 in rule all (line 3 v36.g) to rule a\r
- #2 in rule a (line 8 v36.g) to rule c\r
- #3 in rule c (line 11 v36.g)\r
-\r
- #endif\r
- &&\r
- #if 0\r
-\r
- pred << LATEXT(1)>>? depth=k=1 rule b line 15 v36.g\r
-\r
- set context:\r
- X\r
- tree context: null\r
-\r
- #endif\r
- ======================================================================\r
- Example of "-info p" with the default -prc setting ( "-prc off")\r
- ======================================================================\r
- #if 0\r
-\r
- OR\r
- pred << LATEXT(1)>>? depth=k=1 rule c line 11 v36.g\r
-\r
- set context:\r
- nil\r
- tree context: null\r
-\r
- pred << LATEXT(1)>>? depth=k=1 rule b line 15 v36.g\r
-\r
- set context:\r
- nil\r
- tree context: null\r
-\r
- #endif\r
- ======================================================================\r
- Example of "-info p" with "-prc on" and "-mrhoist off"\r
- ======================================================================\r
- #if 0\r
-\r
- OR\r
- pred << LATEXT(1)>>? depth=k=1 rule c line 11 v36.g\r
-\r
- set context:\r
- B\r
- tree context: null\r
-\r
- pred << LATEXT(1)>>? depth=k=1 rule b line 15 v36.g\r
-\r
- set context:\r
- X\r
- tree context: null\r
-\r
- #endif\r
- ======================================================================\r
-\r
-#97. (Fixed in 1.33MR10) "Predicate applied for more than one ... "\r
-\r
- In 1.33 vanilla, the grammar listed below produced this message for\r
- the first alternative (only) of rule "b":\r
-\r
- warning: predicate applied for >1 lookahead 1-sequences\r
- [you may only want one lookahead 1-sequence to apply.\r
- Try using a context guard '(...)? =>'\r
-\r
- In 1.33MR10 the message is issued for both alternatives.\r
-\r
- top : (a)*;\r
- a : b | c ;\r
-\r
- b : <<PPP(LATEXT(1))>>? ( AAA | BBB )\r
- | <<QQQ(LATEXT(1))>>? ( XXX | YYY )\r
- ;\r
-\r
- c : AAA | XXX;\r
-\r
-#96. (Fixed in 1.33MR10) Guard predicates ignored when -prc off\r
-\r
- Prior to 1.33MR10, guard predicate code was not generated unless\r
- "-prc on" was selected.\r
-\r
- This was incorrect, since "-prc off" (the default) is supposed to\r
- disable only AUTOMATIC computation of predicate context, not the\r
- programmer specified context supplied by guard predicates.\r
-\r
-#95. (Fixed in 1.33MR10) Predicate guard context length was k, not max(k,ck)\r
-\r
- Prior to 1.33MR10, predicate guards were computed to k tokens rather\r
- than max(k,ck). Consider the following grammar:\r
-\r
- a : ( A B C)? => <<AAA(LATEXT(1))>>? (A|X) (B|Y) (C|Z) ;\r
-\r
- The code generated by 1.33 vanilla with "-k 1 -ck 3 -prc on"\r
- for the predicate in "a" resembles:\r
-\r
- if ( (! LA(1)==A) || AAA(LATEXT(1))) {...\r
-\r
- With 1.33MR10 and the same options the code resembles:\r
-\r
- if ( (! (LA(1)==A && LA(2)==B && LA(3)==C) || AAA(LATEXT(1))) {...\r
-\r
-#94. (Fixed in 1.33MR10) Predicates followed by rule references\r
-\r
- Prior to 1.33MR10, a semantic predicate which referenced a token\r
- which was off the end of the rule caused an incomplete context\r
- to be computed (with "-prc on") for the predicate under some circum-\r
- stances. In some cases this manifested itself as illegal C code\r
- (e.g. "LA(2)==[Ep](1)" in the k=2 examples below:\r
-\r
- all : ( a ) *;\r
-\r
- a : <<AAA(LATEXT(2))>>? ID X\r
- | <<BBB(LATEXT(2))>>? Y\r
- | Z\r
- ;\r
-\r
- This might also occur when the semantic predicate was followed\r
- by a rule reference which was shorter than the length of the\r
- semantic predicate:\r
-\r
- all : ( a ) *;\r
-\r
- a : <<AAA(LATEXT(2))>>? ID X\r
- | <<BBB(LATEXT(2))>>? y\r
- | Z\r
- ;\r
-\r
- y : Y ;\r
-\r
- Depending on circumstance, the resulting context might be too\r
- generous because it was too short, or too restrictive because\r
- of missing alternatives.\r
-\r
-#93. (Changed in 1.33MR10) Definition of Purify macro\r
-\r
- Ofer Ben-Ami (gremlin@cs.huji.ac.il) has supplied a definition\r
- for the Purify macro:\r
-\r
- #define PURIFY(r, s) memset((char *) &(r), '\0', (s));\r
-\r
- Note: This may not be the right thing to do for C++ objects that\r
- have constructors. Reported by Bonny Rais (bonny@werple.net.au).\r
-\r
- For those cases one should #define PURIFY to an empty macro in the\r
- #header or #first actions.\r
-\r
-#92. (Fixed in 1.33MR10) Guarded predicates and hoisting\r
-\r
- When a guarded predicate participates in hoisting it is linked into\r
- a predicate expression tree. Prior to 1.33MR10 this link was never\r
- cleared and the next time the guard was used to construct a new\r
- tree the link could contain a spurious reference to another element\r
- which had previosly been joined to it in the semantic predicate tree.\r
-\r
- For example:\r
-\r
- start : ( all ) *;\r
- all : ( a | b ) ;\r
-\r
- start2 : ( all2 ) *;\r
- all2 : ( a ) ;\r
-\r
- a : (A)? => <<AAA(LATEXT(1))>>? A ;\r
- b : (B)? => <<BBB(LATEXT(1))>>? B ;\r
-\r
- Prior to 1.33MR10 the code for "start2" would include a spurious\r
- reference to the BBB predicate which was left from constructing\r
- the predicate tree for rule "start" (i.e. or(AAA,BBB) ).\r
-\r
- In 1.33MR10 this problem is avoided by cloning the original guard\r
- each time it is linked into a predicate tree.\r
-\r
-#91. (Changed in 1.33MR10) Extensive changes to semantic pred hoisting\r
-\r
- ============================================\r
- This has been rendered obsolete by Item #117\r
- ============================================\r
-\r
-#90. (Fixed in 1.33MR10) Semantic pred with LT(i) and i>max(k,ck)\r
-\r
- There is a bug in antlr 1.33 vanilla and all maintenance releases\r
- prior to 1.33MR10 which allows semantic predicates to reference\r
- an LT(i) or LATEXT(i) where i is larger than max(k,ck). When\r
- this occurs antlr will attempt to mark the ith element of an array\r
- in which there are only max(k,ck) elements. The result cannot\r
- be predicted.\r
-\r
- Using LT(i) or LATEXT(i) for i>max(k,ck) is reported as an error\r
- in 1.33MR10.\r
-\r
-#89. Rescinded\r
-\r
-#88. (Fixed in 1.33MR10) Tokens used in semantic predicates in guess mode\r
-\r
- Consider the behavior of a semantic predicate during guess mode:\r
-\r
- rule : a:A (\r
- <<test($a)>>? b:B\r
- | c:C\r
- );\r
-\r
- Prior to MR10 the assignment of the token or attribute to\r
- $a did not occur during guess mode, which would cause the\r
- semantic predicate to misbehave because $a would be null.\r
-\r
- In 1.33MR10 a semantic predicate with a reference to an\r
- element label (such as $a) forces the assignment to take\r
- place even in guess mode.\r
-\r
- In order to work, this fix REQUIRES use of the $label format\r
- for token pointers and attributes referenced in semantic\r
- predicates.\r
-\r
- The fix does not apply to semantic predicates using the\r
- numeric form to refer to attributes (e.g. <<test($1)>>?).\r
- The user will receive a warning for this case.\r
-\r
- Reported by Rob Trout (trout@mcs.cs.kent.edu).\r
-\r
-#87. (Fixed in 1.33MR10) Malformed guard predicates\r
-\r
- Context guard predicates may contain only references to\r
- tokens. They may not contain references to (...)+ and\r
- (...)* blocks. This is now checked. This replaces the\r
- fatal error message in item #78 with an appropriate\r
- (non-fatal) error messge.\r
-\r
- In theory, context guards should be allowed to reference\r
- rules. However, I have not had time to fix this.\r
- Evaluation of the guard takes place before all rules have\r
- been read, making it difficult to resolve a forward reference\r
- to rule "zzz" - it hasn't been read yet ! To postpone evaluation\r
- of the guard until all rules have been read is too much\r
- for the moment.\r
-\r
-#86. (Fixed in 1.33MR10) Unequal set size in set_sub\r
-\r
- Routine set_sub() in pccts/support/set/set.h did not work\r
- correctly when the sets were of unequal sizes. Rewrote\r
- set_equ to make it simpler and remove unnecessary and\r
- expensive calls to set_deg(). This routine was not used\r
- in 1.33 vanila.\r
-\r
-#85. (Changed in 1.33MR10) Allow redefinition of MaxNumFiles\r
-\r
- Raised the maximum number of input files to 99 from 20.\r
- Put a #ifndef/#endif around the "#define MaxNumFiles 99".\r
-\r
-#84. (Fixed in 1.33MR10) Initialize zzBadTok in macro zzRULE\r
-\r
- Initialize zzBadTok to NULL in zzRULE macro of AParser.h.\r
- in order to get rid of warning messages.\r
-\r
-#83. (Fixed in 1.33MR10) False warnings with -w2 for #tokclass\r
-\r
- When -w2 is selected antlr gives inappropriate warnings about\r
- #tokclass names not having any associated regular expressions.\r
- Since a #tokclass is not a "real" token it will never have an\r
- associated regular expression and there should be no warning.\r
-\r
- Reported by Derek Pappas (derek.pappas@eng.sun.com)\r
-\r
-#82. (Fixed in 1.33MR10) Computation of follow sets with multiple cycles\r
-\r
- Reinier van den Born (reinier@vnet.ibm.com) reported a problem\r
- in the computation of follow sets by antlr. The problem (bug)\r
- exists in 1.33 vanilla and all maintenance releases prior to 1.33MR10.\r
-\r
- The problem involves the computation of follow sets when there are\r
- cycles - rules which have mutual references. I believe the problem\r
- is restricted to cases where there is more than one cycle AND\r
- elements of those cycles have rules in common. Even when this\r
- occurs it may not affect the code generated - but it might. It\r
- might also lead to undetected ambiguities.\r
-\r
- There were no changes in antlr or dlg output from the revised version.\r
-\r
- The following fragment demonstates the problem by giving different\r
- follow sets (option -pa) for var_access when built with k=1 and ck=2 on\r
- 1.33 vanilla and 1.33MR10:\r
-\r
- echo_statement : ECHO ( echo_expr )*\r
- ;\r
-\r
- echo_expr : ( command )?\r
- | expression\r
- ;\r
-\r
- command : IDENTIFIER\r
- { concat }\r
- ;\r
-\r
- expression : operand ( OPERATOR operand )*\r
- ;\r
-\r
- operand : value\r
- | START command END\r
- ;\r
-\r
- value : concat\r
- | TYPE operand\r
- ;\r
-\r
- concat : var_access { CONCAT value }\r
- ;\r
-\r
- var_access : IDENTIFIER { INDEX }\r
-\r
- ;\r
-#81. (Changed in 1.33MR10) C mode use of attributes and ASTs\r
-\r
- Reported by Isaac Clark (irclark@mindspring.com).\r
-\r
- C mode code ignores attributes returned by rules which are\r
- referenced using element labels when ASTs are enabled (-gt option).\r
-\r
- 1. start : r:rule t:Token <<$start=$r;>>\r
-\r
- The $r refrence will not work when combined with\r
- the -gt option.\r
-\r
- 2. start : t:Token <<$start=$t;>>\r
-\r
- The $t reference works in all cases.\r
-\r
- 3. start : rule <<$0=$1;>>\r
-\r
- Numeric labels work in all cases.\r
-\r
- With MR10 the user will receive an error message for case 1 when\r
- the -gt option is used.\r
-\r
-#80. (Fixed in 1.33MR10) (...)? as last alternative of block\r
-\r
- A construct like the following:\r
-\r
- rule : a\r
- | (b)?\r
- ;\r
-\r
- does not make sense because there is no alternative when\r
- the guess block fails. This is now reported as a warning\r
- to the user.\r
-\r
- Previously, there was a code generation error for this case:\r
- the guess block was not "closed" when the guess failed.\r
- This could cause an infinite loop or other problems. This\r
- is now fixed.\r
-\r
- Example problem:\r
-\r
- #header<<\r
- #include <stdio.h>\r
- #include "charptr.h"\r
- >>\r
-\r
- <<\r
- #include "charptr.c"\r
- main ()\r
- {\r
- ANTLR(start(),stdin);\r
- }\r
- >>\r
-\r
- #token "[\ \t]+" << zzskip(); >>\r
- #token "[\n]" << zzline++; zzskip(); >>\r
-\r
- #token Word "[a-z]+"\r
- #token Number "[0-9]+"\r
-\r
-\r
- start : (test1)?\r
- | (test2)?\r
- ;\r
- test1 : (Word Word Word Word)?\r
- | (Word Word Word Number)?\r
- ;\r
- test2 : (Word Word Number Word)?\r
- | (Word Word Number Number)?\r
- ;\r
-\r
- Test data which caused infinite loop:\r
-\r
- a 1 a a\r
-\r
-#79. (Changed in 1.33MR10) Use of -fh with multiple parsers\r
-\r
- Previously, antlr always used the pre-processor symbol\r
- STDPCCTS_H as a gate for the file stdpccts.h. This\r
- caused problems when there were multiple parsers defined\r
- because they used the same gate symbol.\r
-\r
- In 1.33MR10, the -fh filename is used to generate the\r
- gate file for stdpccts.h. For instance:\r
-\r
- antlr -fh std_parser1.h\r
-\r
- generates the pre-processor symbol "STDPCCTS_std_parser1_H".\r
-\r
- Reported by Ramanathan Santhanam (ps@kumaran.com).\r
-\r
-#78. (Changed in 1.33MR9) Guard predicates that refer to rules\r
-\r
- ------------------------\r
- Please refer to Item #87\r
- ------------------------\r
-\r
- Guard predicates are processed during an early phase\r
- of antlr (during parsing) before all data structures\r
- are completed.\r
-\r
- There is an apparent bug in earlier versions of 1.33\r
- which caused guard predicates which contained references\r
- to rules (rather than tokens) to reference a structure\r
- which hadn't yet been initialized.\r
-\r
- In some cases (perhaps all cases) references to rules\r
- in guard predicates resulted in the use of "garbage".\r
-\r
-#79. (Changed in 1.33MR9) Jeff Vincent (JVincent@novell.com)\r
-\r
- Previously, the maximum length file name was set\r
- arbitrarily to 300 characters in antlr, dlg, and sorcerer.\r
-\r
- The config.h file now attempts to define the maximum length\r
- filename using _MAX_PATH from stdlib.h before falling back\r
- to using the value 300.\r
-\r
-#78. (Changed in 1.33MR9) Jeff Vincent (JVincent@novell.com)\r
-\r
- Put #ifndef/#endif around definition of ZZLEXBUFSIZE in\r
- antlr.\r
-\r
-#77. (Changed in 1.33MR9) Arithmetic overflow for very large grammars\r
-\r
- In routine HandleAmbiguities() antlr attempts to compute the\r
- number of possible elements in a set that is order of\r
- number-of-tokens raised to the number-of-lookahead-tokens power.\r
- For large grammars or large lookahead (e.g. -ck 7) this can\r
- cause arithmetic overflow.\r
-\r
- With 1.33MR9, arithmetic overflow in this computation is reported\r
- the first time it happens. The program continues to run and\r
- the program branches based on the assumption that the computed\r
- value is larger than any number computed by counting actual cases\r
- because 2**31 is larger than the number of bits in most computers.\r
-\r
- Before 1.33MR9 overflow was not reported. The behavior following\r
- overflow is not predictable by anyone but the original author.\r
-\r
- NOTE\r
-\r
- In 1.33MR10 the warning message is suppressed.\r
- The code which detects the overflow allows the\r
- computation to continue without an error. The\r
- error message itself made made users worry.\r
-\r
-#76. (Changed in 1.33MR9) Jeff Vincent (JVincent@novell.com)\r
-\r
- Jeff Vincent has convinced me to make ANTLRCommonToken and\r
- ANTLRCommonNoRefCountToken use variable length strings\r
- allocated from the heap rather than fixed length strings.\r
- By suitable definition of setText(), the copy constructor,\r
- and operator =() it is possible to maintain "copy" semantics.\r
- By "copy" semantics I mean that when a token is copied from\r
- an existing token it receives its own, distinct, copy of the\r
- text allocated from the heap rather than simply a pointer\r
- to the original token's text.\r
-\r
- ============================================================\r
- W * A * R * N * I * N * G\r
- ============================================================\r
-\r
- It is possible that this may cause problems for some users.\r
- For those users I have included the old version of AToken.h as\r
- pccts/h/AToken_traditional.h.\r
-\r
-#75. (Changed in 1.33MR9) Bruce Guenter (bruceg@qcc.sk.ca)\r
-\r
- Make DLGStringInput const correct. Since this is infrequently\r
- subclassed, it should affect few users, I hope.\r
-\r
-#74. (Changed in 1.33MR9) -o (output directory) option\r
-\r
- Antlr does not properly handle the -o output directory option\r
- when the filename of the grammar contains a directory part. For\r
- example:\r
-\r
- antlr -o outdir pccts_src/myfile.g\r
-\r
- causes antlr create a file called "outdir/pccts_src/myfile.cpp.\r
- It SHOULD create outdir/myfile.cpp\r
-\r
- The suggested code fix has been installed in antlr, dlg, and\r
- Sorcerer.\r
-\r
-#73. (Changed in 1.33MR9) Hoisting of semantic predicates and -mrhoist\r
-\r
- ============================================\r
- This has been rendered obsolete by Item #117\r
- ============================================\r
-\r
-#72. (Changed in 1.33MR9) virtual saveState()/restoreState()/guess_XXX\r
-\r
- The following methods in ANTLRParser were made virtual at\r
- the request of S. Bochnak (S.Bochnak@microTool.com.pl):\r
-\r
- saveState() and restoreState()\r
- guess(), guess_fail(), and guess_done()\r
-\r
-#71. (Changed in 1.33MR9) Access to omitted command line argument\r
-\r
- If a switch requiring arguments is the last thing on the\r
- command line, and the argument is omitted, antlr would core.\r
-\r
- antlr test.g -prc\r
-\r
- instead of\r
-\r
- antlr test.g -prc off\r
-\r
-#70. (Changed in 1.33MR9) Addition of MSVC .dsp and .mak build files\r
-\r
- The following MSVC .dsp and .mak files for pccts and sorcerer\r
- were contributed by Stanislaw Bochnak (S.Bochnak@microTool.com.pl)\r
- and Jeff Vincent (JVincent@novell.com)\r
-\r
- PCCTS Distribution Kit\r
- ----------------------\r
- pccts/PCCTSMSVC50.dsw\r
-\r
- pccts/antlr/AntlrMSVC50.dsp\r
- pccts/antlr/AntlrMSVC50.mak\r
-\r
- pccts/dlg/DlgMSVC50.dsp\r
- pccts/dlg/DlgMSVC50.mak\r
-\r
- pccts/support/msvc.dsp\r
-\r
- Sorcerer Distribution Kit\r
- -------------------------\r
- pccts/sorcerer/SorcererMSVC50.dsp\r
- pccts/sorcerer/SorcererMSVC50.mak\r
-\r
- pccts/sorcerer/lib/msvc.dsp\r
-\r
-#69. (Changed in 1.33MR9) Change "unsigned int" to plain "int"\r
-\r
- Declaration of max_token_num in misc.c as "unsigned int"\r
- caused comparison between signed and unsigned ints giving\r
- warning message without any special benefit.\r
-\r
-#68. (Changed in 1.33MR9) Add void return for dlg internal_error()\r
-\r
- Get rid of "no return value" message in internal_error()\r
- in file dlg/support.c and dlg/dlg.h.\r
-\r
-#67. (Changed in Sor) sor.g: lisp() has no return value\r
-\r
- Added a "void" for the return type.\r
-\r
-#66. (Added to Sor) sor.g: ZZLEXBUFSIZE enclosed in #ifndef/#endif\r
-\r
- A user needed to be able to change the ZZLEXBUFSIZE for\r
- sor. Put the definition of ZZLEXBUFSIZE inside #ifndef/#endif\r
-\r
-#65. (Changed in 1.33MR9) PCCTSAST::deepCopy() and ast_dup() bug\r
-\r
- Jeff Vincent (JVincent@novell.com) found that deepCopy()\r
- made new copies of only the direct descendents. No new\r
- copies were made of sibling nodes, Sibling pointers are\r
- set to zero by shallowCopy().\r
-\r
- PCCTS_AST::deepCopy() has been changed to make a\r
- deep copy in the traditional sense.\r
-\r
- The deepCopy() routine depends on the behavior of\r
- shallowCopy(). In all sor examples I've found,\r
- shallowCopy() zeroes the right and down pointers.\r
-\r
- Original Tree Original deepCopy() Revised deepCopy\r
- ------------- ------------------- ----------------\r
- a->b->c A A\r
- | | |\r
- d->e->f D D->E->F\r
- | | |\r
- g->h->i G G->H->I\r
- | |\r
- j->k J->K\r
-\r
- While comparing deepCopy() for C++ mode with ast_dup for\r
- C mode I found a problem with ast_dup().\r
-\r
- Routine ast_dup() has been changed to make a deep copy\r
- in the traditional sense.\r
-\r
- Original Tree Original ast_dup() Revised ast_dup()\r
- ------------- ------------------- ----------------\r
- a->b->c A->B->C A\r
- | | |\r
- d->e->f D->E->F D->E->F\r
- | | |\r
- g->h->i G->H->I G->H->I\r
- | | |\r
- j->k J->K J->K\r
-\r
-\r
- I believe this affects transform mode sorcerer programs only.\r
-\r
-#64. (Changed in 1.33MR9) anltr/hash.h prototype for killHashTable()\r
-\r
-#63. (Changed in 1.33MR8) h/charptr.h does not zero pointer after free\r
-\r
- The charptr.h routine now zeroes the pointer after free().\r
-\r
- Reported by Jens Tingleff (jensting@imaginet.fr)\r
-\r
-#62. (Changed in 1.33MR8) ANTLRParser::resynch had static variable\r
-\r
- The static variable "consumed" in ANTLRParser::resynch was\r
- changed into an instance variable of the class with the\r
- name "resynchConsumed".\r
-\r
- Reported by S.Bochnak@microTool.com.pl\r
-\r
-#61. (Changed in 1.33MR8) Using rule>[i,j] when rule has no return values\r
-\r
- Previously, the following code would cause antlr to core when\r
- it tried to generate code for rule1 because rule2 had no return\r
- values ("upward inheritance"):\r
-\r
- rule1 : <<int i; int j>>\r
- rule2 > [i,j]\r
- ;\r
-\r
- rule2 : Anything ;\r
-\r
- Reported by S.Bochnak@microTool.com.pl\r
-\r
- Verified correct operation of antlr MR8 when missing or extra\r
- inheritance arguments for all combinations. When there are\r
- missing or extra arguments code will still be generated even\r
- though this might cause the invocation of a subroutine with\r
- the wrong number of arguments.\r
-\r
-#60. (Changed in 1.33MR7) Major changes to exception handling\r
-\r
- There were significant problems in the handling of exceptions\r
- in 1.33 vanilla. The general problem is that it can only\r
- process one level of exception handler. For example, a named\r
- exception handler, an exception handler for an alternative, or\r
- an exception for a subrule always went to the rule's exception\r
- handler if there was no "catch" which matched the exception.\r
-\r
- In 1.33MR7 the exception handlers properly "nest". If an\r
- exception handler does not have a matching "catch" then the\r
- nextmost outer exception handler is checked for an appropriate\r
- "catch" clause, and so on until an exception handler with an\r
- appropriate "catch" is found.\r
-\r
- There are still undesirable features in the way exception\r
- handlers are implemented, but I do not have time to fix them\r
- at the moment:\r
-\r
- The exception handlers for alternatives are outside the\r
- block containing the alternative. This makes it impossible\r
- to access variables declared in a block or to resume the\r
- parse by "falling through". The parse can still be easily\r
- resumed in other ways, but not in the most natural fashion.\r
-\r
- This results in an inconsistentcy between named exception\r
- handlers and exception handlers for alternatives. When\r
- an exception handler for an alternative "falls through"\r
- it goes to the nextmost outer handler - not the "normal\r
- action".\r
-\r
- A major difference between 1.33MR7 and 1.33 vanilla is\r
- the default action after an exception is caught:\r
-\r
- 1.33 Vanilla\r
- ------------\r
- In 1.33 vanilla the signal value is set to zero ("NoSignal")\r
- and the code drops through to the code following the exception.\r
- For named exception handlers this is the "normal action".\r
- For alternative exception handlers this is the rule's handler.\r
-\r
- 1.33MR7\r
- -------\r
- In 1.33MR7 the signal value is NOT automatically set to zero.\r
-\r
- There are two cases:\r
-\r
- For named exception handlers: if the signal value has been\r
- set to zero the code drops through to the "normal action".\r
-\r
- For all other cases the code branches to the nextmost outer\r
- exception handler until it reaches the handler for the rule.\r
-\r
- The following macros have been defined for convenience:\r
-\r
- C/C++ Mode Name\r
- --------------------\r
- (zz)suppressSignal\r
- set signal & return signal arg to 0 ("NoSignal")\r
- (zz)setSignal(intValue)\r
- set signal & return signal arg to some value\r
- (zz)exportSignal\r
- copy the signal value to the return signal arg\r
-\r
- I'm not sure why PCCTS make a distinction between the local\r
- signal value and the return signal argument, but I'm loathe\r
- to change the code. The burden of copying the local signal\r
- value to the return signal argument can be given to the\r
- default signal handler, I suppose.\r
-\r
-#59. (Changed in 1.33MR7) Prototypes for some functions\r
-\r
- Added prototypes for the following functions to antlr.h\r
-\r
- zzconsumeUntil()\r
- zzconsumeUntilToken()\r
-\r
-#58. (Changed in 1.33MR7) Added defintion of zzbufsize to dlgauto.h\r
-\r
-#57. (Changed in 1.33MR7) Format of #line directive\r
-\r
- Previously, the -gl directive for line 1234 would\r
- resemble: "# 1234 filename.g". This caused problems\r
- for some compilers/pre-processors. In MR7 it generates\r
- "#line 1234 filename.g".\r
-\r
-#56. (Added in 1.33MR7) Jan Mikkelsen <janm@zeta.org.au>\r
-\r
- Move PURIFY macro invocaton to after rule's init action.\r
-\r
-#55. (Fixed in 1.33MR7) Unitialized variables in ANTLRParser\r
-\r
- Member variables inf_labase and inf_last were not initialized.\r
- (See item #50.)\r
-\r
-#54. (Fixed in 1.33MR6) Brad Schick (schick@interacess.com)\r
-\r
- Previously, the following constructs generated the same\r
- code:\r
-\r
- rule1 : (A B C)?\r
- | something-else\r
- ;\r
-\r
- rule2 : (A B C)? ()\r
- | something-else\r
- ;\r
-\r
- In all versions of pccts rule1 guesses (A B C) and then\r
- consume all three tokens if the guess succeeds. In MR6\r
- rule2 guesses (A B C) but consumes NONE of the tokens\r
- when the guess succeeds because "()" matches epsilon.\r
-\r
-#53. (Explanation for 1.33MR6) What happens after an exception is caught ?\r
-\r
- The Book is silent about what happens after an exception\r
- is caught.\r
-\r
- The following code fragment prints "Error Action" followed\r
- by "Normal Action".\r
-\r
- test : Word ex:Number <<printf("Normal Action\n");>>\r
- exception[ex]\r
- catch NoViableAlt:\r
- <<printf("Error Action\n");>>\r
- ;\r
-\r
- The reason for "Normal Action" is that the normal flow of the\r
- program after a user-written exception handler is to "drop through".\r
- In the case of an exception handler for a rule this results in\r
- the exection of a "return" statement. In the case of an\r
- exception handler attached to an alternative, rule, or token\r
- this is the code that would have executed had there been no\r
- exception.\r
-\r
- The user can achieve the desired result by using a "return"\r
- statement.\r
-\r
- test : Word ex:Number <<printf("Normal Action\n");>>\r
- exception[ex]\r
- catch NoViableAlt:\r
- <<printf("Error Action\n"); return;>>\r
- ;\r
-\r
- The most powerful mechanism for recovery from parse errors\r
- in pccts is syntactic predicates because they provide\r
- backtracking. Exceptions allow "return", "break",\r
- "consumeUntil(...)", "goto _handler", "goto _fail", and\r
- changing the _signal value.\r
-\r
-#52. (Fixed in 1.33MR6) Exceptions without syntactic predicates\r
-\r
- The following generates bad code in 1.33 if no syntactic\r
- predicates are present in the grammar.\r
-\r
- test : Word ex:Number <<printf("Normal Action\n");>>\r
- exception[ex]\r
- catch NoViableAlt:\r
- <<printf("Error Action\n");>>\r
-\r
- There is a reference to a guess variable. In C mode\r
- this causes a compiler error. In C++ mode it generates\r
- an extraneous check on member "guessing".\r
-\r
- In MR6 correct code is generated for both C and C++ mode.\r
-\r
-#51. (Added to 1.33MR6) Exception operator "@" used without exceptions\r
-\r
- In MR6 added a warning when the exception operator "@" is\r
- used and no exception group is defined. This is probably\r
- a case where "\@" or "@" is meant.\r
-\r
-#50. (Fixed in 1.33MR6) Gunnar Rxnning (gunnar@candleweb.no)\r
- http://www.candleweb.no/~gunnar/\r
-\r
- Routines zzsave_antlr_state and zzrestore_antlr_state don't\r
- save and restore all the data needed when switching states.\r
-\r
- Suggested patch applied to antlr.h and err.h for MR6.\r
-\r
-#49. (Fixed in 1.33MR6) Sinan Karasu (sinan@boeing.com)\r
-\r
- Generated code failed to turn off guess mode when leaving a\r
- (...)+ block which contained a guess block. The result was\r
- an infinite loop. For example:\r
-\r
- rule : (\r
- (x)?\r
- | y\r
- )+\r
-\r
- Suggested code fix implemented in MR6. Replaced\r
-\r
- ... else if (zzcnt>1) break;\r
-\r
- with:\r
-\r
- C++ mode:\r
- ... else if (zzcnt>1) {if (!zzrv) zzGUESS_DONE; break;};\r
- C mode:\r
- ... else if (zzcnt>1) {if (zzguessing) zzGUESS_DONE; break;};\r
-\r
-#48. (Fixed in 1.33MR6) Invalid exception element causes core\r
-\r
- A label attached to an invalid construct can cause\r
- pccts to crash while processing the exception associated\r
- with the label. For example:\r
-\r
- rule : t:(B C)\r
- exception[t] catch MismatchedToken: <<printf(...);>>\r
-\r
- Version MR6 generates the message:\r
-\r
- reference in exception handler to undefined label 't'\r
-\r
-#47. (Fixed in 1.33MR6) Manuel Ornato\r
-\r
- Under some circumstances involving a k >1 or ck >1\r
- grammar and a loop block (i.e. (...)* ) pccts will\r
- fail to detect a syntax error and loop indefinitely.\r
- The problem did not exist in 1.20, but has existed\r
- from 1.23 to the present.\r
-\r
- Fixed in MR6.\r
-\r
- ---------------------------------------------------\r
- Complete test program\r
- ---------------------------------------------------\r
- #header<<\r
- #include <stdio.h>\r
- #include "charptr.h"\r
- >>\r
-\r
- <<\r
- #include "charptr.c"\r
- main ()\r
- {\r
- ANTLR(global(),stdin);\r
- }\r
- >>\r
-\r
- #token "[\ \t]+" << zzskip(); >>\r
- #token "[\n]" << zzline++; zzskip(); >>\r
-\r
- #token B "b"\r
- #token C "c"\r
- #token D "d"\r
- #token E "e"\r
- #token LP "\("\r
- #token RP "\)"\r
-\r
- #token ANTLREOF "@"\r
-\r
- global : (\r
- (E liste)\r
- | liste\r
- | listed\r
- ) ANTLREOF\r
- ;\r
-\r
- listeb : LP ( B ( B | C )* ) RP ;\r
- listec : LP ( C ( B | C )* ) RP ;\r
- listed : LP ( D ( B | C )* ) RP ;\r
- liste : ( listeb | listec )* ;\r
-\r
- ---------------------------------------------------\r
- Sample data causing infinite loop\r
- ---------------------------------------------------\r
- e (d c)\r
- ---------------------------------------------------\r
-\r
-#46. (Fixed in 1.33MR6) Robert Richter\r
- (Robert.Richter@infotech.tu-chemnitz.de)\r
-\r
- This item from the list of known problems was\r
- fixed by item #18 (below).\r
-\r
-#45. (Fixed in 1.33MR6) Brad Schick (schick@interaccess.com)\r
-\r
- The dependency scanner in VC++ mistakenly sees a\r
- reference to an MPW #include file even though properly\r
- #ifdef/#endif in config.h. The suggested workaround\r
- has been implemented:\r
-\r
- #ifdef MPW\r
- .....\r
- #define MPW_CursorCtl_Header <CursorCtl.h>\r
- #include MPW_CursorCtl_Header\r
- .....\r
- #endif\r
-\r
-#44. (Fixed in 1.33MR6) cast malloc() to (char *) in charptr.c\r
-\r
- Added (char *) cast for systems where malloc returns "void *".\r
-\r
-#43. (Added to 1.33MR6) Bruce Guenter (bruceg@qcc.sk.ca)\r
-\r
- Add setLeft() and setUp methods to ASTDoublyLinkedBase\r
- for symmetry with setRight() and setDown() methods.\r
-\r
-#42. (Fixed in 1.33MR6) Jeff Katcher (jkatcher@nortel.ca)\r
-\r
- C++ style comment in antlr.c corrected.\r
-\r
-#41. (Added in 1.33MR6) antlr -stdout\r
-\r
- Using "antlr -stdout ..." forces the text that would\r
- normally go to the grammar.c or grammar.cpp file to\r
- stdout.\r
-\r
-#40. (Added in 1.33MR6) antlr -tab to change tab stops\r
-\r
- Using "antlr -tab number ..." changes the tab stops\r
- for the grammar.c or grammar.cpp file. The number\r
- must be between 0 and 8. Using 0 gives tab characters,\r
- values between 1 and 8 give the appropriate number of\r
- space characters.\r
-\r
-#39. (Fixed in 1.33MR5) Jan Mikkelsen <janm@zeta.org.au>\r
-\r
- Commas in function prototype still not correct under\r
- some circumstances. Suggested code fix installed.\r
-\r
-#38. (Fixed in 1.33MR5) ANTLRTokenBuffer constructor\r
-\r
- Have ANTLRTokenBuffer ctor initialize member "parser" to null.\r
-\r
-#37. (Fixed in 1.33MR4) Bruce Guenter (bruceg@qcc.sk.ca)\r
-\r
- In ANTLRParser::FAIL(int k,...) released memory pointed to by\r
- f[i] (as well as f itself. Should only free f itself.\r
-\r
-#36. (Fixed in 1.33MR3) Cortland D. Starrett (cort@shay.ecn.purdue.edu)\r
-\r
- Neglected to properly declare isDLGmaxToken() when fixing problem\r
- reported by Andreas Magnusson.\r
-\r
- Undo "_retv=NULL;" change which caused problems for return values\r
- from rules whose return values weren't pointers.\r
-\r
- Failed to create bin directory if it didn't exist.\r
-\r
-#35. (Fixed in 1.33MR2) Andreas Magnusson\r
-(Andreas.Magnusson@mailbox.swipnet.se)\r
-\r
- Repair bug introduced by 1.33MR1 for #tokdefs. The original fix\r
- placed "DLGmaxToken=9999" and "DLGminToken=0" in the TokenType enum\r
- in order to fix a problem with an aggresive compiler assigning an 8\r
- bit enum which might be too narrow. This caused #tokdefs to assume\r
- that there were 9999 real tokens. The repair to the fix causes antlr to\r
- ignore TokenTypes "DLGmaxToken" and "DLGminToken" in a #tokdefs file.\r
-\r
-#34. (Added to 1.33MR1) Add public DLGLexerBase::set_line(int newValue)\r
-\r
- Previously there was no public function for changing the line\r
- number maintained by the lexer.\r
-\r
-#33. (Fixed in 1.33MR1) Franklin Chen (chen@adi.com)\r
-\r
- Accidental use of EXIT_FAILURE rather than PCCTS_EXIT_FAILURE\r
- in pccts/h/AParser.cpp.\r
-\r
-#32. (Fixed in 1.33MR1) Franklin Chen (chen@adi.com)\r
-\r
- In PCCTSAST.cpp lines 405 and 466: Change\r
-\r
- free (t)\r
- to\r
- free ( (char *)t );\r
-\r
- to match prototype.\r
-\r
-#31. (Added to 1.33MR1) Pointer to parser in ANTLRTokenBuffer\r
- Pointer to parser in DLGLexerBase\r
-\r
- The ANTLRTokenBuffer class now contains a pointer to the\r
- parser which is using it. This is established by the\r
- ANTLRParser constructor calling ANTLRTokenBuffer::\r
- setParser(ANTLRParser *p).\r
-\r
- When ANTLRTokenBuffer::setParser(ANTLRParser *p) is\r
- called it saves the pointer to the parser and then\r
- calls ANTLRTokenStream::setParser(ANTLRParser *p)\r
- so that the lexer can also save a pointer to the\r
- parser.\r
-\r
- There is also a function getParser() in each class\r
- with the obvious purpose.\r
-\r
- It is possible that these functions will return NULL\r
- under some circumstances (e.g. a non-DLG lexer is used).\r
-\r
-#30. (Added to 1.33MR1) function tokenName(int token) standard\r
-\r
- The generated parser class now includes the\r
- function:\r
-\r
- static const ANTLRChar * tokenName(int token)\r
-\r
- which returns a pointer to the "name" corresponding\r
- to the token.\r
-\r
- The base class (ANTLRParser) always includes the\r
- member function:\r
-\r
- const ANTLRChar * parserTokenName(int token)\r
-\r
- which can be accessed by objects which have a pointer\r
- to an ANTLRParser, but do not know the name of the\r
- parser class (e.g. ANTLRTokenBuffer and DLGLexerBase).\r
-\r
-#29. (Added to 1.33MR1) Debugging DLG lexers\r
-\r
- If the pre-processor symbol DEBUG_LEXER is defined\r
- then DLexerBase will include code for printing out\r
- key information about tokens which are recognized.\r
-\r
- The debug feature of the lexer is controlled by:\r
-\r
- int previousDebugValue=lexer.debugLexer(newValue);\r
-\r
- a value of 0 disables output\r
- a value of 1 enables output\r
-\r
- Even if the lexer debug code is compiled into DLexerBase\r
- it must be enabled before any output is generated. For\r
- example:\r
-\r
- DLGFileInput in(stdin);\r
- MyDLG lexer(&in,2000);\r
-\r
- lexer.setToken(&aToken);\r
-\r
- #if DEBUG_LEXER\r
- lexer.debugLexer(1); // enable debug information\r
- #endif\r
-\r
-#28. (Added to 1.33MR1) More control over DLG header\r
-\r
- Version 1.33MR1 adds the following directives to PCCTS\r
- for C++ mode:\r
-\r
- #lexprefix <<source code>>\r
-\r
- Adds source code to the DLGLexer.h file\r
- after the #include "DLexerBase.h" but\r
- before the start of the class definition.\r
-\r
- #lexmember <<source code>>\r
-\r
- Adds source code to the DLGLexer.h file\r
- as part of the DLGLexer class body. It\r
- appears immediately after the start of\r
- the class and a "public: statement.\r
-\r
-#27. (Fixed in 1.33MR1) Comments in DLG actions\r
-\r
- Previously, DLG would not recognize comments as a special case.\r
- Thus, ">>" in the comments would cause errors. This is fixed.\r
-\r
-#26. (Fixed in 1.33MR1) Removed static variables from error routines\r
-\r
- Previously, the existence of statically allocated variables\r
- in some of the parser's member functions posed a danger when\r
- there was more than one parser active.\r
-\r
- Replaced with dynamically allocated/freed variables in 1.33MR1.\r
-\r
-#25. (Fixed in 1.33MR1) Use of string literals in semantic predicates\r
-\r
- Previously, it was not possible to place a string literal in\r
- a semantic predicate because it was not properly "stringized"\r
- for the report of a failed predicate.\r
-\r
-#24. (Fixed in 1.33MR1) Continuation lines for semantic predicates\r
-\r
- Previously, it was not possible to continue semantic\r
- predicates across a line because it was not properly\r
- "stringized" for the report of a failed predicate.\r
-\r
- rule : <<ifXYZ()>>?[ a very\r
- long statement ]\r
-\r
-#23. (Fixed in 1.33MR1) {...} envelope for failed semantic predicates\r
-\r
- Previously, there was a code generation error for failed\r
- semantic predicates:\r
-\r
- rule : <<xyz()>>?[ stmt1; stmt2; ]\r
-\r
- which generated code which resembled:\r
-\r
- if (! xyz()) stmt1; stmt2;\r
-\r
- It now puts the statements in a {...} envelope:\r
-\r
- if (! xyz()) { stmt1; stmt2; };\r
-\r
-#22. (Fixed in 1.33MR1) Continuation of #token across lines using "\"\r
-\r
- Previously, it was not possible to continue a #token regular\r
- expression across a line. The trailing "\" and newline caused\r
- a newline to be inserted into the regular expression by DLG.\r
-\r
- Fixed in 1.33MR1.\r
-\r
-#21. (Fixed in 1.33MR1) Use of ">>" (right shift operator in DLG actions\r
-\r
- It is now possible to use the C++ right shift operator ">>"\r
- in DLG actions by using the normal escapes:\r
-\r
- #token "shift-right" << value=value \>\> 1;>>\r
-\r
-#20. (Version 1.33/19-Jan-97 Karl Eccleson <karle@microrobotics.co.uk>\r
- P.A. Keller (P.A.Keller@bath.ac.uk)\r
-\r
- There is a problem due to using exceptions with the -gh option.\r
-\r
- Suggested fix now in 1.33MR1.\r
-\r
-#19. (Fixed in 1.33MR1) Tom Piscotti and John Lilley\r
-\r
- There were problems suppressing messages to stdin and stdout\r
- when running in a window environment because some functions\r
- which uses fprint were not virtual.\r
-\r
- Suggested change now in 1.33MR1.\r
-\r
- I believe all functions containing error messages (excluding those\r
- indicating internal inconsistency) have been placed in functions\r
- which are virtual.\r
-\r
-#18. (Version 1.33/ 22-Nov-96) John Bair (jbair@iftime.com)\r
-\r
- Under some combination of options a required "return _retv" is\r
- not generated.\r
-\r
- Suggested fix now in 1.33MR1.\r
-\r
-#17. (Version 1.33/3-Sep-96) Ron House (house@helios.usq.edu.au)\r
-\r
- The routine ASTBase::predorder_action omits two "tree->"\r
- prefixes, which results in the preorder_action belonging\r
- to the wrong node to be invoked.\r
-\r
- Suggested fix now in 1.33MR1.\r
-\r
-#16. (Version 1.33/7-Jun-96) Eli Sternheim <eli@interhdl.com>\r
-\r
- Routine consumeUntilToken() does not check for end-of-file\r
- condition.\r
-\r
- Suggested fix now in 1.33MR1.\r
-\r
-#15. (Version 1.33/8 Apr 96) Asgeir Olafsson <olafsson@cstar.ac.com>\r
-\r
- Problem with tree duplication of doubly linked ASTs in ASTBase.cpp.\r
-\r
- Suggested fix now in 1.33MR1.\r
-\r
-#14. (Version 1.33/28-Feb-96) Andreas.Magnusson@mailbox.swipnet.se\r
-\r
- Problem with definition of operator = (const ANTLRTokenPtr rhs).\r
-\r
- Suggested fix now in 1.33MR1.\r
-\r
-#13. (Version 1.33/13-Feb-96) Franklin Chen (chen@adi.com)\r
-\r
- Sun C++ Compiler 3.0.1 can't compile testcpp/1 due to goto in\r
- block with destructors.\r
-\r
- Apparently fixed. Can't locate "goto".\r
-\r
-#12. (Version 1.33/10-Nov-95) Minor problems with 1.33 code\r
-\r
- The following items have been fixed in 1.33MR1:\r
-\r
- 1. pccts/antlr/main.c line 142\r
-\r
- "void" appears in classic C code\r
-\r
- 2. no makefile in support/genmk\r
-\r
- 3. EXIT_FAILURE/_SUCCESS instead of PCCTS_EXIT_FAILURE/_SUCCESS\r
-\r
- pccts/h/PCCTSAST.cpp\r
- pccts/h/DLexerBase.cpp\r
- pccts/testcpp/6/test.g\r
-\r
- 4. use of "signed int" isn't accepted by AT&T cfront\r
-\r
- pccts/h/PCCTSAST.h line 42\r
-\r
- 5. in call to ANTLRParser::FAIL the var arg err_k is passed as\r
- "int" but is declared "unsigned int".\r
-\r
- 6. I believe that a failed validation predicate still does not\r
- get put in a "{...}" envelope, despite the release notes.\r
-\r
- 7. The #token ">>" appearing in the DLG grammar description\r
- causes DLG to generate the string literal "\>\>" which\r
- is non-conforming and will cause some compilers to\r
- complain (scan.c function act10 line 143 of source code).\r
-\r
-#11. (Version 1.32b6) Dave Kuhlman (dkuhlman@netcom.com)\r
-\r
- Problem with file close in gen.c. Already fixed in 1.33.\r
-\r
-#10. (Version 1.32b6/29-Aug-95)\r
-\r
- pccts/antlr/main.c contains a C++ style comments on lines 149\r
- and 176 which causes problems for most C compilers.\r
-\r
- Already fixed in 1.33.\r
-\r
-#9. (Version 1.32b4/14-Mar-95) dlgauto.h #include "config.h"\r
-\r
- The file pccts/h/dlgauto.h should probably contain a #include\r
- "config.h" as it uses the #define symbol __USE_PROTOS.\r
-\r
- Added to 1.33MR1.\r
-\r
-#8. (Version 1.32b4/6-Mar-95) Michael T. Richter (mtr@igs.net)\r
-\r
- In C++ output mode anonymous tokens from in-line regular expressions\r
- can create enum values which are too wide for the datatype of the enum\r
- assigned by the C++ compiler.\r
-\r
- Fixed in 1.33MR1.\r
-\r
-#7. (Version 1.32b4/6-Mar-95) C++ does not imply __STDC__\r
-\r
- In err.h the combination of # directives assumes that a C++\r
- compiler has __STDC__ defined. This is not necessarily true.\r
-\r
- This problem also appears in the use of __USE_PROTOS which\r
- is appropriate for both Standard C and C++ in antlr/gen.c\r
- and antlr/lex.c\r
-\r
- Fixed in 1.33MR1.\r
-\r
-#6. (Version 1.32 ?/15-Feb-95) Name conflict for "TokenType"\r
-\r
- Already fixed in 1.33.\r
-\r
-#5. (23-Jan-95) Douglas_Cuthbertson.JTIDS@jtids_qmail.hanscom.af.mil\r
-\r
- The fail action following a semantic predicate is not enclosed in\r
- "{...}". This can lead to problems when the fail action contains\r
- more than one statement.\r
-\r
- Fixed in 1.33MR1.\r
-\r
-#4 . (Version 1.33/31-Mar-96) jlilley@empathy.com (John Lilley)\r
-\r
- Put briefly, a semantic predicate ought to abort a guess if it fails.\r
-\r
- Correction suggested by J. Lilley has been added to 1.33MR1.\r
-\r
-#3 . (Version 1.33) P.A.Keller@bath.ac.uk\r
-\r
- Extra commas are placed in the K&R style argument list for rules\r
- when using both exceptions and ASTs.\r
-\r
- Fixed in 1.33MR1.\r
-\r
-#2. (Version 1.32b6/2-Oct-95) Brad Schick <schick@interaccess.com>\r
-\r
- Construct #[] generates zzastnew() in C++ mode.\r
-\r
- Already fixed in 1.33.\r
-\r
-#1. (Version 1.33) Bob Bailey (robert@oakhill.sps.mot.com)\r
-\r
- Previously, config.h assumed that all PC systems required\r
- "short" file names. The user can now override that\r
- assumption with "#define LONGFILENAMES".\r
-\r
- Added to 1.33MR1.\r
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