AFAIR one needs to pass
-std=gnu17
which should suffice.
Best regards
Norbert
On Mon, 14 Jul 2025, Simon McVittie wrote:
> Package: libkpathsea-dev
> Version: 2024.20240313.70630+ds-6
> Severity: important
> Tags: ftbfs upstream forky sid
> Control: block 1096597 by -1
> Control: affects -1 + src:evince
>
> In #1096597, Matthias Klose reported that evince FTBFS with gcc-15 as
> default (it is not the default for trixie, but will become the default
> in forky). This seems to be caused by libkpathsea-dev's headers,
> combined with gcc-15 defaulting to C23.
>
> As an example of the class of issue I'm reporting, libkpathsea-dev's
> c-std.h has this:
>
> >#ifdef HAVE_STDLIB_H
> >#include <stdlib.h>
> >/* Include <stdlib.h> before <stddef.h>, to help avoid NULL
> > redefinitions on some systems. (We don't include <stddef.h>
> > ourselves any more, but FYI.) */
> >#else
> >/* It's impossible to say for sure what the system will deign to put in
> > <stdlib.h>, but let's hope it's at least this. */
> >extern char *getenv ();
> >#endif /* not HAVE_STDLIB_H */
>
> and evince includes <stdlib.h> followed by <kpathsea/c-std.h>.
>
> The code in c-std.h assumes that the build system of every dependent
> package will check for stdlib.h and define HAVE_STDLIB_H if found, but
> there is a tendency to stop doing that, and instead assume that all
> platforms comply with a 1989 C standard by now. In particular Evince
> does not check for <stdlib.h>, and includes it unconditionally (I
> assume).
>
> In C11 or older, `extern char *getenv ()` declares getenv() as a
> function taking unspecified parameters and returning a string, but in
> C23 it declares getenv() as a function taking *no* parameters and
> returning a string, hence the compiler sees this as a declaration that
> is incompatible with the one it already saw in <stdlib.h>, and errors
> out:
>
> >/usr/include/kpathsea/c-std.h:48:14: error: conflicting types for ‘getenv’;
> >have ‘char *(void)’
> > 48 | extern char *getenv ();
> > | ^~~~~~
>
> An equivalent failure mode is seen in the evince build log for other
> Standard C functions like strtok() and strstr(). There might be others,
> I didn't inspect all of the kpathsea headers.
>
> evince could presumably work around this by conditionally or
> unconditionally defining HAVE_STDLIB_H, etc., before it includes
> kpathsea headers; but it shouldn't have to, because each library should
> be self-contained.
>
> I think <kpathsea/c-std.h> should do something more like this
> (pseudo-patch, untested) so that it treats __STDC__ as implying that
> every Standard C header is present:
>
> -#ifdef HAVE_STDLIB_H
> +#if defined(__STDC__) || defined(HAVE_STDLIB_H)
> #include <stdlib.h>
> ...
>
> (or it could check __STDC_VERSION__ if preferred)
>
> ... or it could just assume that every platform has Standard C headers
> by now, since C89 is several decades old.
>
> Thanks,
> smcv
>
--
DI Dr Norbert Preining https://www.preining.info
arXiv / Cornell University + IFMGA Guide + TU Wien + TeX Live
GPG: 0x860CDC13 fp: F7D8 A928 26E3 16A1 9FA0 ACF0 6CAC A448 860C DC13
