Re: Add new macro gl_WARN_ADD_MULTIPLE

[Bruno Haible]

Hi Tim,

> Mentioned 2 years ago (but being still too busy to make a gnulib module
> from it); Wget2's implementation using --help=warnings is here and FSF
> copyrighted:
> 
> https://gitlab.com/gnuwget/wget2/blob/master/m4/wget_manywarnings.m4
> 
> And how to use / fine-tune it can be seen in L106 of
> 
> https://gitlab.com/gnuwget/wget2/blob/master/configure.ac

Does this implementation of manywarnings support only the case where
you want all possible warnings except an explicitly specified set?
Or also the case where you want only an explicitly specified set of
warnings?
Although I think that the first approach is the better one in the long
run, some projects may want to use the second approach, and the gnulib
module so far supports both approaches.

> There is gcc and clang support.

This way of detecting clang is not portable:

    case $CC in
      *gcc*) CCNAME="gcc";;
      *clang*) CCNAME="clang";;
    esac

On FreeBSD, for example, $CC = "cc" is clang but you cannot know it
by looking at the command name. You need to run the preprocessor and
see how it processes
  #if defined __clang__

Bruno