Re: warning: module to simplify adding compiler warnings

[Simon Josefsson]

Bruno Haible <address@hidden> writes:

> Simon Josefsson wrote:
>> It allows me to add to configure.ac this:
>> 
>> gl_WARN_ADD([-Wall])
>> gl_WARN_ADD([-Wpointer-arith])
>> gl_WARN_ADD([-Wstrict-prototypes])
>> gl_WARN_ADD([-Wno-pointer-sign])
>
> Will $WARN_CFLAGS be used before or after $CFLAGS? I.e. can the user
> disable these warning flags or not?

That's up to each maintainer, WARN_CFLAGS isn't added to CFLAGS
automatically.  I'm using this in libtasn1's src/Makefile.am:

AM_CFLAGS = $(WARN_CFLAGS)
AM_CPPFLAGS = -I$(top_srcdir)/lib -I$(top_srcdir)/gl -I$(top_builddir)/gl
...

This makes it possible to gradually fix code, just add $(WARN_CFLAGS) in
those directories that you've solved all warnings for.  (For example, in
some projects the gnulib directory triggers warning that I would want to
fix elsewhere in the project, but I don't want the build to fail because
of the gnulib code.)

>> gl_WARN_ADD([-Werror])
>
> This is a bad idea. It will cause gratuitous frustration for users on
> platforms that you haven't tested. Remember that many warnings do not
> indicate something really wrong with the program, only the _possibility_
> that something is wrong. The user will then need two attempts to build a
> package, instead of only one. Or he will choose to build with a proprietary
> compiler rather than with gcc.
>
> IMO this is just the opposite of portability.

I agree, however, -Werror is useful during 'make distcheck'.  I'm going
to remove the above line from configure.ac and pass the flag to
configure in cfg.mk instead.

> It would be better to make the macro bail out at autoconf time if someone
> attempts to put gl_WARN_ADD([-Werror]) into his configure.ac file.

This is too much, I think, and would break an IMHO realistic use-case of
putting -Werror in WARN_CFLAGS during make distcheck.

I've pushed the module.

/Simon