Message-Id: <199906011820.SAA19762@out4.ibm.net>
From: "Mark E." <snowball3 AT bigfoot DOT com>
To: djgpp-workers AT delorie DOT com
Date: Tue, 1 Jun 1999 14:22:04 -0400
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Subject: Re: enhancements to fcntl.c
References: <199905311824 DOT SAA72470 AT out2 DOT ibm DOT net>
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Reply-To: djgpp-workers AT delorie DOT com

Eli,
Thanks for running the tests.

I've created a macro to detect when the optional arguments are 
present. But I don't know how portable across compiler versions it is:

#define __dj_HAVE_OPTIONAL_ARGS(x) \
  ((int *)__builtin_frame_address(1) - (int *)__builtin_next_arg(x) - 2)


where x is the last non-optional argument. An example:

void func_with_opt_args(int x, ...)
{
  if (__dj_HAVE_OPTIONAL_ARGS(x))
    printf("Have optional args.\n");
  else
    printf("Do not have optional args.\n");
}

int main()
{
  func_with_optional_args(1, 2);
  func_with_optional_args(1);
  return 0;
}

If it is portable between different compiler versions, the macro could be 
used in open and fcntl to avoid reading arguments from the stack that 
aren't there.

--- 
Mark Elbrecht, snowball3 AT bigfoot DOT com
http://snowball.frogspace.net/