[swift-corelibs-dev] Defining _GNU_SOURCE for module-map-included headers

[Dan Stenmark]

I'm trying to invoke Linux's unshare() system call from Swift, but without much success.  From C, it requires _GNU_SOURCE to be #define'd before the #include <sched.h>.  The Glibc module map does indeed include sched.h, so the lack of _GNU_SOURCE appears to be the likely culprit.  What's the appropriate action to take here?

Dan