Restructuring for better separation of Tool packages.

[mirror_edk2.git] / Tools / CodeTools / TianoTools / Pccts / KNOWN_PROBLEMS.txt

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    =======================================================\r
    Known Problems In PCCTS - Last revised 14 November 1998\r
    =======================================================\r
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#17. The dlg fix for handling characters up to 255 is incorrect.\r
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    See item #207.\r
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    Reported by Frank Hartmann.\r
        \r
#16. A note about "&&" predicates (Mike Dimmick)\r
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    Mike Dimmick has pointed out a potential pitfall in the use of the\r
    "&&" style predicate.  Consider:\r
    \r
         r0: (g)? => <<P>>?  r1\r
             | ...\r
             ;\r
         r1: A | B;\r
         \r
    If the context guard g is not a subset of the lookahead context for r1\r
    (in other words g is neither A nor B) then the code may execute r1 \r
    even when the lookahead context is not satisfied.  This is an error\r
    by the person coding the grammer, and the error should be reported to\r
    the user, but it isn't. expect.  Some examples I've run seem to\r
    indicate that such an error actually results in the rule becoming\r
    unreachable.\r
    \r
    When g is properly coded the code is correct, the problem is when g\r
    is not properly coded.\r
    \r
    A second problem reported by Mike Dimmick is that the test for a\r
    failed validation predicate is equivalent to a test on the predicate\r
    along.  In other words, if the "&&" has not been hoisted then it may\r
    falsely report a validation error.\r
\r
#15. (Changed in MR23) Warning for LT(i), LATEXT(i) in token match actions\r
\r
    An bug (or at least an oddity) is that a reference to LT(1), LA(1),\r
    or LATEXT(1) in an action which immediately follows a token match\r
    in a rule refers to the token matched, not the token which is in\r
    the lookahead buffer.  Consider:\13\r
\r
        r : abc <<action alpha>> D <<action beta>> E;\r
\r
    In this case LT(1) in action alpha will refer to the next token in\r
    the lookahead buffer ("D"), but LT(1) in action beta will refer to\r
    the token matched by D - the preceding token.\r
\r
    A warning has been added which warns users about this when an action\r
    following a token match contains a reference to LT(1), LA(1), or LATEXT(1).\r
\r
    This behavior should be changed, but it appears in too many programs\r
    now.  Another problem, perhaps more significant, is that the obvious\r
    fix (moving the consume() call to before the action) could change the \r
    order in which input is requested and output appears in existing programs.\r
\r
    This problem was reported, along with a fix by Benjamin Mandel\r
    (beny@sd.co.il).  However, I felt that changing the behavior was too\r
    dangerous for existing code.\r
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#14. Parsing bug in dlg\r
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    THM: I have been unable to reproduce this problem.\r
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    Reported by Rick Howard Mijenix Corporation (rickh@mijenix.com).\r
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    The regular expression parser (in rexpr.c) fails while\r
    trying to parse the following regular expression:\r
\r
            {[a-zA-Z]:}(\\\\[a-zA-Z0-9]*)+\r
\r
    See my comment in the following excerpt from rexpr.c:\r
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    /*\r
     * <regExpr>        ::= <andExpr> ( '|' {<andExpr>} )*\r
     *\r
     * Return -1 if syntax error\r
     * Return  0 if none found\r
     * Return  1 if a regExrp was found\r
     */\r
	static\r
	regExpr(g)\r
	GraphPtr g;\r
	{\r
	    Graph g1, g2;\r
	\r
	    if ( andExpr(&g1) == -1 )\r
	    {\r
	        return -1;\r
	    }\r
	\r
	    while ( token == '|' )\r
	    {\r
	        int a;\r
	        next();\r
	        a = andExpr(&g2);\r
	        if ( a == -1 ) return -1;   /* syntax error below */\r
	        else if ( !a ) return 1;    /* empty alternative */\r
	        g1 = BuildNFA_AorB(g1, g2);\r
	    }\r
	\r
	    if ( token!='\0' ) return -1;\r
	*****\r
	***** It appears to fail here becuause token is 125 - the closing '}'\r
	***** If I change it to:\r
	*****    if ( token!='\0' && token!='}' && token!= ')' ) return -1;\r
	*****\r
	***** It succeeds, but I'm not sure this is the corrrect approach.\r
	*****\r
	    *g = g1;\r
	    return 1;\r
	}\r
\r
#13. dlg reports an invalid range for: [\0x00-\0xff]\r
\r
    Diagnosed by Piotr Eljasiak (eljasiak@no-spam.zt.gdansk.tpsa.pl):\r
\r
    Fixed in MR16.\r
\r
#12. Strings containing comment actions\r
\r
     Sequences that looked like C style comments appearing in string\r
     literals are improperly parsed by antlr/dlg.\r
\r
        << fprintf(out," /* obsolete */ ");\r
\r
     For this case use:\r
\r
        << fprintf(out," \/\* obsolete \*\/ ");\r
\r
     Reported by K.J. Cummings (cummings@peritus.com).\r
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#11. User hook for deallocation of variables on guess fail\r
\r
     The mechanism outlined in Item #108 works only for\r
     heap allocated variables.\r
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#10. Label re-initialization in ( X {y:Y} )*\r
\r
     If a label assignment is optional and appears in a\r
     (...)* or (...)+ block it will not be reset to NULL\r
     when it is skipped by a subsequent iteration.\r
\r
     Consider the example:\r
\r
            ( X { y:Y })* Z\r
\r
     with input:\r
\r
            X Y X Z\r
\r
     The first time through the block Y will be matched and\r
     y will be set to point to the token.  On the second\r
     iteration of the (...)* block there is no match for Y.\r
     But y will not be reset to NULL, as the user might\r
     expect, it will contain a reference to the Y that was\r
     matched in the first iteration.\r
\r
     The work-around is to manually reset y:\r
\r
            ( X << y = NULL; >> { y:Y } )* Z\r
\r
        or\r
\r
            ( X ( y:Y | << y = NULL; >> /* epsilon */ ) )* Z\r
\r
     Reported by Jeff Vincent (JVincent@novell.com).\r
\r
#9. PCCTAST.h PCCTSAST::setType() is a noop\r
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#8. #tokdefs with ~Token and .\r
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    THM: I have been unable to reproduce this problem.\r
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    When antlr uses #tokdefs to define tokens the fields of\r
    #errclass and #tokclass do not get properly defined.\r
    When it subsequently attempts to take the complement of\r
    the set of tokens (using ~Token or .) it can refer to\r
    tokens which don't have names, generating a fatal error.\r
\r
#7. DLG crashes on some invalid inputs\r
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    THM:  In MR20 have fixed the most common cases.\r
\r
    The following token defintion will cause DLG to crash.\r
\r
        #token "()"\r
\r
    Reported by  Mengue Olivier (dolmen@bigfoot.com).\r
\r
#6. On MS systems \n\r is treated as two new lines\r
\r
    Fixed.\r
\r
#5. Token expressions in #tokclass\r
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    #errclass does not support TOK1..TOK2 or ~TOK syntax.\r
    #tokclass does not support ~TOKEN syntax\r
\r
    A workaround for #errclass TOK1..TOK2 is to use a\r
    #tokclass.\r
\r
    Reported by Dave Watola (dwatola@amtsun.jpl.nasa.gov)\r
\r
#4. A #tokdef must appear "early" in the grammar file.\r
\r
    The "early" section of the grammar file is the only\r
    place where the following directives may appear:\r
\r
        #header\r
        #first\r
        #tokdefs\r
        #parser\r
\r
    Any other kind of statement signifiies the end of the\r
    "early" section.\r
\r
#3. Use of PURIFY macro for C++ mode\r
\r
    Item #93 of the CHANGES_FROM_1.33 describes the use of\r
    the PURIFY macro to zero arguments to be passed by\r
    upward inheritance.\r
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        #define PURIFY(r, s) memset((char *) &(r), '\0', (s));\r
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    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 be an empty macro\r
    in the #header or #first actions.\r
\r
#2. Fixed in 1.33MR10 - See CHANGES_FROM_1.33 Item #80.\r
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#1. The quality of support for systems with 8.3 file names leaves\r
    much to be desired.  Since the kit is distributed using the\r
    long file names and the make file uses long file names it requires\r
    some effort to generate.  This will probably not be changed due\r
    to the large number of systems already written using the long\r
    file names.\r