cpplib: Suppress warnings in system headers

[Neil Booth]

Zack Weinberg wrote:-

> This seems to be the right general idea.  I have one concern:  I
> believe there are some cpp_pedwarn() calls that are not predicated on
> CPP_PEDANTIC.  These are mandatory warnings that happen to be also
> mandated by ISO C (so we want -pedantic-errors to make them into
> errors).  You need to find these and give them a way to do what they
> need. (cpp_mandatory_pedwarn?  I don't mind the long name, these should
> be rare.)

I don't fully see what you mean.  Are you suggesting that -pedantic-
errors should emit errors even in header files?  Or that

      if (code == PEDWARN)
	{
	  if (! CPP_OPTION (pfile, pedantic))
	    return 0;
	  is_warning = ! CPP_OPTION (pfile, pedantic_errors);
	}

should become

      if (code == PEDWARN)
	{
	  is_warning = ! CPP_OPTION (pfile, pedantic_errors);
	  if (is_warning && ! CPP_OPTION (pfile, pedantic))
	    return 0;
	}

If what you're suggesting requires adding another category (I hope it
doesn't), can we at the same time move to

  cpp_diag ();
  cpp_diag_with_line ();
  cpp_diag_with_file_and_line ();

where each takes an argument indicating severity, and scrap the
cpp_pedwarn, cpp_warning etc.  Otherwise we start to swim in a sea of
endless variations.

Neil.