Use _Unwind_Backtrace on Apple platforms.

Darwin's backtrace() function does not work with sigaltstack (which was
enabled when available with r270395) — it does a sanity check to make
sure that the current frame pointer is within the expected stack area
(which it is not when using an alternate stack) and gives up otherwise.
The alternative of _Unwind_Backtrace seems to work fine on macOS, so use
that when backtrace() fails. Note that we then use backtrace_symbols_fd()
with the addresses from _Unwind_Backtrace, but I’ve tested that and it
also seems to work fine. rdar://problem/28646552

llvm-svn: 286851

diff --git a/llvm/lib/Support/Unix/Signals.inc b/llvm/lib/Support/Unix/Signals.inc
index 9752b70..3750d7f 100644 (file)
--- a/llvm/lib/Support/Unix/Signals.inc
+++ b/llvm/lib/Support/Unix/Signals.inc
@@ -48,7 +48,7 @@
 // _Unwind_Backtrace function, but on FreeBSD the configure test passes
 // despite the function not existing, and on Android, <unwind.h> conflicts
 // with <link.h>.
-#ifdef __GLIBC__
+#if defined(__GLIBC__) || defined(__APPLE__)
 #include <unwind.h>
 #else
 #undef HAVE__UNWIND_BACKTRACE