According to http://gcc.gnu.org/viewcvs?view=revision&revision=178892 this seems to be an issue with the Makefile, so porting the change mentioned in that URL should fix the issue. Reproducible: Always Steps to Reproduce: 1. Install sys-deve/gcc-4.6.2 2. Include /usr/lib/gcc/i686-pc-linux-gnu/4.6.2/plugin/include/cp/cp-tree.h in a source file 3. Try to compile Actual Results: /usr/lib/gcc/i686-pc-linux-gnu/4.6.2/plugin/include/cp/cp-tree.h:43:31: fatal error: c-family/c-common.h: No such file or directory Expected Results: It should be able to find the c-common.h header file, which is acutally located at /usr/lib/gcc/i686-pc-linux-gnu/4.6.2/plugin/include/c-common.h I found this trying to compile Mozilla's Dehydra in a Sabayon installation. After symlinking c-common.h and c-pretty-print.h in the right places, everything went on fine.
*** Bug 396433 has been marked as a duplicate of this bug. ***
http://sources.gentoo.org/viewcvs.py/gentoo/src/patchsets/gcc/4.6.2/gentoo/76_all_4.7.0_c-family-headers.patch?rev=1.1&view=markup
Fixed in 4.6.3_p1.4.