RE: C99 implies -Wimplicit-function-declaration?

["Gary Funck" <gary at intrepid dot com>]

Joseph S. Myers wrote (in part):
> No prototype is different from no declaration at all.  Implicit function 
> declarations are not part of C99, so the code is in error in C99 mode.

OK, thanks. I (now) understand that the reference to a warning about a missing protoype
does not apply.  However, I don't see anything in section 6.5.2.2
(rev. 1999-12-01) that says that a function declaration or prototype
declaration must (or should) precede a call to the function. And GCC isn't treating it
as an error, but rather is enabling the warning by default.

The code reads as follows (in c-objc-common.c):

  /* If still unspecified, make it match -std=c99
     (allowing for -pedantic-errors).  */
  if (mesg_implicit_function_declaration < 0)
    {
      if (flag_isoc99)
        mesg_implicit_function_declaration = flag_pedantic_errors ? 2 : 1;
      else
        mesg_implicit_function_declaration = 0;
    }

And mesg_implicit_function_declaration is initialized to -1 (c-common.c):

/* Nonzero means message about use of implicit function declarations;
 1 means warning; 2 means error.  */

int mesg_implicit_function_declaration = -1;