Remove check for uncaught exception

Summary: This check is causing some issues in github commits. Figuring out exactly which versions of 4.9 have the bug is a pain, so let's just get rid of it. See D6695110 for more context.

Reviewed By: yfeldblum

Differential Revision: D7431713

fbshipit-source-id: 17d1b025edf52592495c5f69c5a15025b33b3895

folly/Portability.h

@@ -354,13 +354,6 @@ constexpr auto kMicrosoftAbiVer = FOLLY_MICROSOFT_ABI_VER;
 constexpr auto kMicrosoftAbiVer = 0;
 #endif
 
-// TODO: Remove when removing support for gcc4.9
-#if __GLIBCXX__ && __GLIBCXX__ == 20150123
-constexpr auto kIsGlib49 = true;
-#else
-constexpr auto kIsGlib49 = false;
-#endif
-
 // cpplib is an implementation of the standard library, and is the one typically
 // used with the msvc compiler
 #if _CPPLIB_VER

folly/fibers/Fiber.cpp

@@ -171,8 +171,6 @@ void Fiber::preempt(State state) {
     DCHECK_EQ(state_, RUNNING);
     DCHECK_NE(state, RUNNING);
     DCHECK(!std::current_exception());
-    // std::uncaught_exception is broken in libstdc++ v4.9
-    DCHECK(kIsGlib49 || !std::uncaught_exception());
 
     state_ = state;