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[mirror_edk2.git] / StdLib / Include / stdarg.h

/** @file\r
  The header <stdarg.h> declares a type and defines three macros, for advancing\r
  through a list of arguments whose number and types are not known to the\r
  called function when it is translated.\r
\r
  A function may be called with a variable number of arguments of varying types.\r
  Its parameter list contains one or more parameters.  The rightmost parameter\r
  plays a special role in the access mechanism, and will be designated paramN\r
  in this description.\r
\r
  The type va_list is a type suitable for holding information needed by the\r
  macros va_start, va_arg, and va_end.  If access to the varying arguments\r
  is desired, the called function shall declare an object (referred to as ap\r
  in these descriptions) having type va_list.  The object ap may be passed as\r
  an argument to another function; if that function invokes the va_arg macro\r
  with parameter ap, the value of ap in the calling function is indeterminate\r
  and shall be passed to the va_end macro prior to any further reference to ap.\r
\r
  The va_start and va_arg macros shall be implemented as macros, not as actual\r
  functions.  It is unspecified, by the C library standards, whether va_end\r
  is a macro or an identifier declared with external linkage.  If a macro\r
  definition is suppressed in order to access an actual function, or a\r
  program defines an external identifier with the name va_end, the behavior\r
  is undefined.  The va_start and va_end macros shall be invoked in the\r
  function accepting a varying number of arguments, if access to the varying\r
  arguments is desired.\r
\r
Copyright (c) 2010, Intel Corporation. All rights reserved.<BR>\r
This program and the accompanying materials are licensed and made available under\r
the terms and conditions of the BSD License that accompanies this distribution.\r
The full text of the license may be found at\r
http://opensource.org/licenses/bsd-license.php.\r
\r
THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
\r
**/\r
#ifndef _STDARG_H\r
#define _STDARG_H\r
#include  <sys/EfiCdefs.h>\r
\r
/** The type va_list is a type suitable for holding information needed by the\r
    macros va_start, va_arg, and va_end.\r
**/\r
#if defined(__GNUC__)\r
typedef __builtin_va_list   va_list;\r
#else\r
#define va_list   VA_LIST\r
#endif\r
\r
/** The va_start macro shall be invoked before any access to the unnamed arguments.\r
    The va_start macro initializes ap for subsequent use by va_arg and va_end.\r
\r
    Synopsys: void va_start(va_list ap, paramN);\r
\r
    @param  ap      An object of type va_list that is to be initialized such\r
                    that subsequent successive invocations of va_arg will\r
                    return the values of the parameters following paramN.\r
\r
    @param  paramN  The parameter paramN is the identifier of the rightmost\r
                    parameter in the variable parameter list in the function\r
                    definition (the one just before the ,...).  If the\r
                    parameter parmN is declared with the register storage\r
                    class, with a function of array type, or with a type that\r
                    is not compatible with the type that results after\r
                    application of the default argument promotions, the\r
                    behavior is undefined.\r
**/\r
#if defined(__GNUC__)\r
#define va_start    __builtin_va_start\r
#else\r
#define va_start    VA_START\r
#endif\r
\r
/** The va_arg macro expands to an expression that has the type and value of\r
    the next argument in the call.  The parameter ap shall be the same as the\r
    va_list ap initialized by va_start.  Each invocation of va_arg modifies ap\r
    so that the values of successive arguments are returned in turn.  The\r
    parameter type is a type name specified such that the type of a pointer to\r
    an object that has the specified type can be obtained simply by postfixing\r
    a * to type.  If there is no actual next argument, or if type is not\r
    compatible with the type of the actual next argument (as promoted\r
    according to the default argument promotions), the behavior is undefined.\r
\r
    Synopsys: type va_arg(va_list ap, type);\r
\r
    @param  ap    An object of type va_list that was initialized by a prior\r
                  invocation of va_start.\r
\r
    @param  type  A type name specifying the type of the parameter to be retrieved.\r
\r
    @return       The first invocation of the va_arg macro after that of the\r
                  va_start macro returns the value of the argument after that\r
                  specified by paramN.  Successive invocations return the values\r
                  of the remaining arguments in succession.\r
**/\r
#if defined(__GNUC__)\r
#define va_arg        __builtin_va_arg\r
#else\r
#define va_arg        VA_ARG\r
#endif\r
\r
/** The va_end macro facillitates a normal return from the function whose\r
    variable argument list was referred to by the expansion of va_start that\r
    initialized the va_list ap.\r
\r
    Synopsys: void va_end(va_list ap);\r
\r
    The va_end macro may modify ap so that it is no longer usable (without an\r
    intervening invocation of va_start).  If there is no corresponding\r
    invocation of the va_start macro, or if the va_end macro is not invoked\r
    before the return, the behavior is undefined.\r
\r
    @param  ap    An object of type va_list, initialized by a prior\r
                  invocation of va_start, that will no longer be referenced.\r
**/\r
#if defined(__GNUC__)\r
#define va_end              __builtin_va_end\r
#else\r
#define va_end              VA_END\r
#endif\r
\r
/** For BSD compatibility. **/\r
#if defined(__GNUC__)\r
#define va_copy         __builtin_va_copy\r
#else\r
#define va_copy(s,d)      (s) = (d)\r
#endif\r
\r
#endif  /* _STDARG_H */\r