Bruno Haible via Gnulib discussion list <bug-gnulib@gnu.org> writes:
> I promised:
>> - see how this new warning behaves on the Gnulib source code
>
> The two good news are:
> - The warning is really helpful. With it, I could find all relevant uses of
> '0' quickly. Patch attached and committed.
> - There were no false positives.
>
> However, there are warnings that are not in the responsibility of a package
> maintainer:
>
> * Anywhere a pthread_mutex_t is initialized, the warning appears. This is
> because on glibc, the macro __PTHREAD_MUTEX_INITIALIZER(__kind)
> expands to
> 0, 0, 0, 0, __kind, 0, 0, { 0, 0 }
> It should better expand to
> 0, 0, 0, 0, __kind, 0, 0, { NULL, NULL }
>
> * gperf generated code has these warnings:
> unicase/special-casing-table.gperf:171:10: warning: zero as null pointer
> constant [-Wzero-as-null-pointer-constant]
> unictype/categ_byname.gperf:115:10: warning: zero as null pointer
> constant [-Wzero-as-null-pointer-constant]
> unictype/incb_byname.gperf:60:10: warning: zero as null pointer constant
> [-Wzero-as-null-pointer-constant]
> unictype/joininggroup_byname.gperf:131:10: warning: zero as null pointer
> constant [-Wzero-as-null-pointer-constant]
> unictype/pr_byname.gperf:114:10: warning: zero as null pointer constant
> [-Wzero-as-null-pointer-constant]
> unictype/scripts_byname.gperf:160:10: warning: zero as null pointer
> constant [-Wzero-as-null-pointer-constant]
> uninorm/composition-table.gperf:995:10: warning: zero as null pointer
> constant [-Wzero-as-null-pointer-constant]
>
> These can only be fixed with a new glibc release and a new gperf release.Thanks for analysis! > So, as things stand now, we can recommend the warning option to package > maintainers. But I am not in favour of letting Gnulib enable it by default, > since it will invariably lead to warnings (in the two cases mentioned above) > that the maintainer cannot silence. Only once there have been glibc + gperf > releases and we have waited 2 years until most maintainers have a system with > these newer releases, will it make sense to enable it by default. Gnulib could also check if glibc/gperf have been updated and enable the warning for those builds, to allow us to catch the problem in CI/CD's and be able to fix the problems earlier. But indeed, it is simpler to ask maintainers to enable -Wzero-as-null-pointer-constant in some CI/CD run and manually filter out errors caused by glibc/gperf. I will experiment with it, when I have find a suitable GCC 15.x container image. /Simon
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