Recently I have been unable to build qemu 2.6.0 as it fails to configure with static-user USE flag. The following error message is printed at configure time of the static-user target: sizeof(size_t) doesn't match GLIB_SIZEOF_SIZE_T. You probably need to set PKG_CONFIG_LIBDIR to point to the right pkg-config files for your build target However, the error has little to do with any glib type-width macros. It is printed because the configure test attempts to link against libpcre which was not built with static-libs since the current glib-2.48.1 ebuild doesn't require it. However, it is a dependency of glib-2.0.pc file so it prevents static QEMUs from configuring against glib-2.0. I manually re-installed libpcre with static-libs and qemu-2.6.0 was able to configure and merge safely with static-user.
[master bcea1ef] dev-libs/glib: libpcre static-libs USE needs to be sync with glib (#588082 by Jordan Yelloz), libintl is needed (#589336 by Gerhard Bräunlich). 1 file changed, 1 insertion(+) rename dev-libs/glib/{glib-2.48.1.ebuild => glib-2.48.1-r1.ebuild} (99%)
*** Bug 590344 has been marked as a duplicate of this bug. ***
*** Bug 588952 has been marked as a duplicate of this bug. ***
This should be fixed for real this time in 2.48.2.