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 193297 [details]
This issue has been mentioned on an openafs mailing list, a proposed patch is here: http://www.openafs.org/pipermail/openafs-devel/2009-April/016587.html
I'm not sure what the plan is for this type of code to get merged upstream.
*** Bug 273025 has been marked as a duplicate of this bug. ***
This should be fixed in net-fs/openafs-1.4.10, in which the patch mentioned in comment #2 has been included.
Thanks for reporting!