pkgconfig: use the -std=gnu90 flag to compile

[06393993]

... otherwise, the compilation of pkgconfig may fail with the following error when compiling glib:

  CC       libglib_2_0_la-goption.lo
goption.c:169:14: error: two or more data types in declaration specifiers
  169 |     gboolean bool;
      |              ^~~~

[cerisier]

Hey there, what is the impact of adding this flag when using newer compilers ? Do you mean that glib is still fully gnu90 ?

[06393993]

Hey there, what is the impact of adding this flag when using newer compilers ?

I think this issue only happens with newer compilers, because bool becomes a keyword in C23¹, and is a macro defined in <stdbool.h> since C99 until C23², so it can't be used as a field name.

I will check with some new compilers I can use recently and update.

Do you mean that glib is still fully gnu90 ?

I don't know the exact C standard they use, but the glib 2.38.2 bundled with pkg-config is checked in 12 years ago³, so we do expect it uses a rather old C standard. Is that what you are asking? Or I can dig into several package manager to see how they compile and report, do you want me to do that?

Footnotes

1. https://en.cppreference.com/w/c/keyword/bool.html ↩

2. https://en.cppreference.com/w/c/types.html ↩

3. https://gitlab.freedesktop.org/pkg-config/pkg-config/-/tree/master/glib?ref_type=heads ↩

[06393993]

Just tried the pkg-config 0.29.2 listed at https://pkgconfig.freedesktop.org/releases/, configure simply with ../configure --with-internal-glib, and build with the make command and the gcc (Debian 15.2.0-3) 15.2.0 compiler, probably released on August 8, 2025¹. It ends up with this exact same error:

./../../glib/glib/goption.c:169:14: error: two or more data types in declaration specifiers
  169 |     gboolean bool;
      |              ^~~~
../../../glib/glib/goption.c:169:18: warning: declaration does not declare anything
  169 |     gboolean bool;
      |                  ^
../../../glib/glib/goption.c: In function ‘free_changes_list’:
../../../glib/glib/goption.c:1603:60: error: expected identifier before ‘bool’
 1603 |               *(gboolean *)change->arg_data = change->prev.bool;
      |                                                            ^~~~

Footnotes

1. https://gcc.gnu.org/releases.html ↩

[06393993]

As of glib itself, they get rename the field from bool to boolean in https://gitlab.gnome.org/GNOME/glib/-/commit/9e320e1c43a4770ed1532248fe5416eb0c618120. And I also look into the pkgconfig package in AUR. They don't use the bundled glib that comes with pkgconfig, and just build ToT glib, so they can build it.