gcc -pedantic ?

I'm trying to compile mozilla thunderbird on -current and the
configure program stops with this error:

checking whether C++ compiler has -pedantic long long bug... yes
configure: error: Your compiler appears to have a known bug where
long long is miscompiled when using -pedantic.
Reconfigure using --disable-pedantic.

Is this related to the new gcc update, or is it a long-time
incompatibility with linux source code?  I'm new at this
cross-compiling stuff, you can probably tell.