Confused by Glib's __attribute__(cleanup) and MSVC compiling

[felixf4xu]

Hi,

I tried to port a GObject/Glib based library to vcpkg, but in its meson.build file it disables msvc compiler. The reason is that Glib is using g_autoptr which is using __attribute__(cleanup) and it's not available in msvc. I understand that, so far.

Then I tried to compile Glib on Windows locally, it compiled with MSVC and it succeeded.

So I was confused. If Glib can't be compiled by MSVC, why in vcpkg default compiling triplet, it succeeded?

[dg0yt]

There is a glib port, and it builds for windows (MSVC) tripelts. And also the glib README indicates that MSVC works, https://github.com/winlibs/glib/blob/master/README.win32. This is what we know.

But we have zero knowledge about this "GObject/Glib based library" you are trying to port. Maybe it is only this software, but not glib itself, which is using g_autoptr? This macro is indeed documented to be "only supported on GCC and clang. This macro is not defined on other compilers and should not be used in programs that are intended to be portable to those compilers.", https://docs.gtk.org/glib/auto-cleanup.html. But this doesn't imply that glib is unsupported on MSVC.

[felixf4xu]

Thanks for the comment, now I understand that vcpkg can build glib itself successfully, because glib only defines g_autoptr but never uses it.

Then I checked GTK source code, I see

• GTK+ types now support the GLib g_autoptr() facility for
  automatic cleanup of automatic variables. GTK+ itself does
  not use g_autoptr() internally.

So I also understood that GTK can be built by vcpkg (msvc).

As to the lib I mentioned which depends on glib, it unfortunately uses g_autoptr, so it can't be built by vcpkg(msvc)