StdLib/Include/stdarg.h

   1 /** @file
   2   The header <stdarg.h> declares a type and defines three macros, for advancing
   3   through a list of arguments whose number and types are not known to the
   4   called function when it is translated.
   5
   6   A function may be called with a variable number of arguments of varying types.
   7   Its parameter list contains one or more parameters.  The rightmost parameter
   8   plays a special role in the access mechanism, and will be designated paramN
   9   in this description.
  10
  11   The type va_list is a type suitable for holding information needed by the
  12   macros va_start, va_arg, and va_end.  If access to the varying arguments
  13   is desired, the called function shall declare an object (referred to as ap
  14   in these descriptions) having type va_list.  The object ap may be passed as
  15   an argument to another function; if that function invokes the va_arg macro
  16   with parameter ap, the value of ap in the calling function is indeterminate
  17   and shall be passed to the va_end macro prior to any further reference to ap.
  18
  19   The va_start and va_arg macros shall be implemented as macros, not as actual
  20   functions.  It is unspecified, by the C library standards, whether va_end
  21   is a macro or an identifier declared with external linkage.  If a macro
  22   definition is suppressed in order to access an actual function, or a
  23   program defines an external identifier with the name va_end, the behavior
  24   is undefined.  The va_start and va_end macros shall be invoked in the
  25   function accepting a varying number of arguments, if access to the varying
  26   arguments is desired.
  27
  28 Copyright (c) 2010, Intel Corporation. All rights reserved.<BR>
  29 This program and the accompanying materials are licensed and made available under
  30 the terms and conditions of the BSD License that accompanies this distribution.
  31 The full text of the license may be found at
  32 http://opensource.org/licenses/bsd-license.php.
  33
  34 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  35 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  36
  37 **/
  38 #ifndef _STDARG_H
  39 #define _STDARG_H
  40 #include  <sys/EfiCdefs.h>
  41
  42 /** The type va_list is a type suitable for holding information needed by the
  43     macros va_start, va_arg, and va_end.
  44
  45     This implementation aliases va_list to VA_LIST, declared in MdePkg/Base.h.
  46 **/
  47 #define va_list   VA_LIST
  48
  49 /** The va_start macro shall be invoked before any access to the unnamed arguments.
  50     The va_start macro initializes ap for subsequent use by va_arg and va_end.
  51
  52     Synopsys: void va_start(va_list ap, paramN);
  53
  54     @param  ap      An object of type va_list that is to be initialized such
  55                     that subsequent successive invocations of va_arg will
  56                     return the values of the parameters following paramN.
  57
  58     @param  paramN  The parameter paramN is the identifier of the rightmost
  59                     parameter in the variable parameter list in the function
  60                     definition (the one just before the ,...).  If the
  61                     parameter parmN is declared with the register storage
  62                     class, with a function of array type, or with a type that
  63                     is not compatible with the type that results after
  64                     application of the default argument promotions, the
  65                     behavior is undefined.
  66
  67     This implementation aliases va_start to VA_START, declared in MdePkg/Base.h.
  68 **/
  69 //#define va_start(ap, ParamN)    VA_START(ap, ParamN)
  70 #define va_start    VA_START
  71
  72 /** The va_arg macro expands to an expression that has the type and value of
  73     the next argument in the call.  The parameter ap shall be the same as the
  74     va_list ap initialized by va_start.  Each invocation of va_arg modifies ap
  75     so that the values of successive arguments are returned in turn.  The
  76     parameter type is a type name specified such that the type of a pointer to
  77     an object that has the specified type can be obtained simply by postfixing
  78     a * to type.  If there is no actual next argument, or if type is not
  79     compatible with the type of the actual next argument (as promoted
  80     according to the default argument promotions), the behavior is undefined.
  81
  82     Synopsys: type va_arg(va_list ap, type);
  83
  84     @param  ap    An object of type va_list that was initialized by a prior
  85                   invocation of va_start.
  86
  87     @param  type  A type name specifying the type of the parameter to be retrieved.
  88
  89     @return       The first invocation of the va_arg macro after that of the
  90                   va_start macro returns the value of the argument after that
  91                   specified by paramN.  Successive invocations return the values
  92                   of the remaining arguments in succession.
  93
  94     This implementation aliases va_arg to VA_ARG, declared in MdePkg/Base.h.
  95 **/
  96 //#define va_arg(ap, type)        VA_ARG(ap, type)
  97 #define va_arg        VA_ARG
  98
  99 /** The va_end macro facillitates a normal return from the function whose
 100     variable argument list was referred to by the expansion of va_start that
 101     initialized the va_list ap.
 102
 103     Synopsys: void va_end(va_list ap);
 104
 105     The va_end macro may modify ap so that it is no longer usable (without an
 106     intervening invocation of va_start).  If there is no corresponding
 107     invocation of the va_start macro, or if the va_end macro is not invoked
 108     before the return, the behavior is undefined.
 109
 110     @param  ap    An object of type va_list, initialized by a prior
 111                   invocation of va_start, that will no longer be referenced.
 112
 113     This implementation aliases va_end to VA_END, declared in MdePkg/Base.h.
 114 **/
 115 //#define va_end(ap)              VA_END(ap)
 116 #define va_end              VA_END
 117
 118 /** For BSD compatibility. **/
 119 #define va_copy(s,d)      (s) = (d)
 120
 121 #endif  /* _STDARG_H */