The x pkg-config .pc files contain -DXOPEN_SOURCE, which breaks the build of several GNOME modules, because it prevents them from using GNU extensions in glibc. Though this might be useful during the X build, it should not be provided via pkg-config. I noticed this on Ubuntu unstable (breezy).
It seems that the xproto.pc file contains the flag: http://cvs.freedesktop.org/xlibs/Xproto/xproto.pc.in?view=markup Due to the way the other xlibs .pc files are written, the flag gets repeated in them too. E.g.: http://cvs.freedesktop.org/xlibs/X11/x11.pc.in?view=markup (this file should be using "Requies: xproto" to pull in the Xproto flags, but that is really another bug). If the _XOPEN_SOURCE symbol is only needed when compiling the xlibs, then it should not be included in the .pc files, since it causes compile problems for applications that use the X libraries but also use some libc symbols that get hidden when _XOPEN_SOURCE is defined. The Gnome mailing list thread in question is here: http://thread.gmane.org/gmane.comp.gnome.desktop/25131
From talking with Daniel Stone, it seems that I gave the wrong viewcvs URL. Breezy is using the xorg X libraries, which have since been fixed: http://cvs.freedesktop.org/xorg/proto/X11/xproto.pc.in?view=markup
Great. So this seems to be fixed.
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