There are a few changes in glibc-2.10 that might make your software fail to build with it, please refer to my blog post  if you're not sure what the problem is.
And no I don't usually provide emerge --info with these bugs because they are caused by glibc-2.10!
Created attachment 194272 [details]
Duplicate of bug #271607 which has a patch (or which ever way you want to mark the duplications to exist).
*** This bug has been marked as a duplicate of bug 271607 ***