gcc 3.4.x in portage has the visibility patch and using -fvisibility-inlines-hidden in general should be safe, but not in the case of wxGTK 2.4.x (I haven't tested 2.5.x). It compiles but compiling anything against it won't work, ie aMule. So please filter -fvisibility-inlines-hidden. Reproducible: Always Steps to Reproduce: 1. 2. 3.
Thanks, Prakash, added to all versions of wxGTK.