[cfe-commits] r42857 - in /cfe/trunk: AST/ASTContext.cpp AST/Builtins.cpp Sema/SemaDecl.cpp include/clang/AST/ASTContext.h include/clang/AST/Builtins.def

[Gabor Greif]

Hi Chris,

looks like the __builtin_va_alist is not a typedef,
but a variable/stack slot.

It arises from expanding

va_start on solaris.

Here is the original function:

void check_empty_format_string(char* buf)
{
  va_list ap;
  va_start(ap,buf);
  vprintf("",ap); // expected-warning {{format string is empty}}
  sprintf(buf,""); // expected-warning {{format string is empty}}
}

And its expansion (clang -E):

void check_empty_format_string(char* buf)
{

  va_list ap;
  (void) (ap = (__va_list) &__builtin_va_alist);

  vprintf("",ap);
  sprintf(buf,"");

}


Here is the portion from /usr/include/iso/stdarg_iso.h
relevant for SPARC:

    55  /*
    56   * Many compilation systems depend upon the use of special functions
    57   * built into the the compilation system to handle variable argument
    58   * lists and stack allocations.  The method to obtain this in SunOS
    59   * is to define the feature test macro "__BUILTIN_VA_ARG_INCR" which
    60   * enables the following special built-in functions:
    61   *  __builtin_alloca
    62   *  __builtin_va_alist
    63   *  __builtin_va_arg_incr
    64   * It is intended that the compilation system define this feature test
    65   * macro, not the user of the system.
    66   *
    67   * The tests on the processor type are to provide a transitional period
    68   * for existing compilation systems, and may be removed in a future
    69   * release.
    70   */
    71  #if (defined(__BUILTIN_VA_ARG_INCR) || defined(__sparc) || \
    72    defined(__i386)) && !defined(__lint)
    73
    74  /*
    75   * Instruction set architectures which use a simple pointer to the
    76   * argument save area share a common implementation.
    77   */
    78  #define va_start(list, name)  (void) (list = (__va_list) &__builtin_va_alist)
    79  #define va_arg(list, mode)  ((mode *)__builtin_va_arg_incr((mode *)list))[0]
    80
    81  #elif defined(__ia64)


I hope this info is sufficient to get started :-)

Cheers,

	Gabor