[Msan] Check returning value of DTLS_Get()

Differential Revision: http://reviews.llvm.org/D6403

llvm-svn: 222818

compiler-rt/lib/msan/msan_thread.cc

@@ -36,6 +36,7 @@ void MsanThread::ClearShadowForThreadStackAndTLS() {
   if (tls_begin_ != tls_end_)
     __msan_unpoison((void *)tls_begin_, tls_end_ - tls_begin_);
   DTLS *dtls = DTLS_Get();
+  CHECK_NE(dtls, 0);
   for (uptr i = 0; i < dtls->dtv_size; ++i)
     __msan_unpoison((void *)(dtls->dtv[i].beg), dtls->dtv[i].size);
 }