Another GCC warning snuck in. Introduced by jsdbg2, probably.
Created attachment 553475 [details] [diff] [review] v1 _GNU_SOURCE is a way for *programs* to specify which signatures they want from GNU system headers that... anyway, it's not what you want here. The compiler's preprocessor badge is __GNUC__.  ...or something? if you care, read on: http://www.gnu.org/s/hello/manual/libc/Feature-Test-Macros.html
I forgot to mention, in case the war room is reading along here: it turns out jsdbg2 is innocent! In fact, it's perfect in every way. Please don't back it out. :)
The above link describes _GNU_SOURCE, but I needed to continue my edumification at http://gcc.gnu.org/onlinedocs/cpp/Common-Predefined-Macros.html I think I knew this, but did a lazy grep for "GNU" and grabbed the first thing that looked relevant. Thanks for the cleanup.