GLib and -Wpedantic

[mpranj]

As mentioned in #4055 (comment) compiling GLib (since 2.70.0) currently causes the following error:

[329/751] Building C object src/bindings/io/glib/CMakeFiles/testio_glib.dir/testio_glib.c.o
FAILED: src/bindings/io/glib/CMakeFiles/testio_glib.dir/testio_glib.c.o 
/usr/local/opt/llvm/bin/clang  -Isrc/include -I../src/include -I../tests/cframework -I../src/bindings/io/glib/SYSTEM -I/usr/local/Cellar/glib/2.70.0/include/glib-2.0 -I/usr/local/Cellar/glib/2.70.0/lib/glib-2.0/include -std=gnu99  -Wno-deprecated-declarations  -Wstrict-prototypes -Werror -Wno-long-long -Wpedantic -Wno-variadic-macros -Wall -Wextra -Wno-overlength-strings -Wsign-compare -Wfloat-equal -Wformat -Wformat-security -Wshadow -Wcomments -Wtrigraphs -Wundef -Wuninitialized -Winit-self -Wsign-compare -Wfloat-equal -O2 -g -DNDEBUG -isysroot /Applications/Xcode-12.5.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.3.sdk -mmacosx-version-min=11.2 -MD -MT src/bindings/io/glib/CMakeFiles/testio_glib.dir/testio_glib.c.o -MF src/bindings/io/glib/CMakeFiles/testio_glib.dir/testio_glib.c.o.d -o src/bindings/io/glib/CMakeFiles/testio_glib.dir/testio_glib.c.o -c ../src/bindings/io/glib/testio_glib.c
In file included from ../src/bindings/io/glib/testio_glib.c:17:
In file included from /usr/local/Cellar/glib/2.70.0/include/glib-2.0/glib.h:30:
In file included from /usr/local/Cellar/glib/2.70.0/include/glib-2.0/glib/galloca.h:32:
/usr/local/Cellar/glib/2.70.0/include/glib-2.0/glib/gtypes.h:463:3: error: '_Static_assert' is a C11 extension [-Werror,-Wc11-extensions]
  G_STATIC_ASSERT(sizeof (unsigned long long) == sizeof (guint64));
  ^
/usr/local/Cellar/glib/2.70.0/include/glib-2.0/glib/gmacros.h:819:31: note: expanded from macro 'G_STATIC_ASSERT'
#define G_STATIC_ASSERT(expr) _Static_assert (expr, "Expression evaluates to false")
                              ^
1 error generated.

After reporting the problem upstream it turns out that GLib does not support the -Wpedantic flag as documented here: https://wiki.gnome.org/Projects/GLib/CompilerRequirements.

They also noted that -std=gnu99 and -Wpedantic should not be used together.

In either case, it seems they will not support -Wpedantic any time soon, so we will at least have to remove the flag where glib is used.

[markus2330]

Thank you for #4067. The proper fix is probably simply to disable -Wpedantic for glib? Similar modifications already exist for swig bindings. 74c3dad can be reverted then.