Index: config-ix.cmake
===================================================================
--- config-ix.cmake
+++ config-ix.cmake
@@ -167,7 +167,8 @@
 check_symbol_exists(futimes sys/time.h HAVE_FUTIMES)
 check_symbol_exists(posix_fallocate fcntl.h HAVE_POSIX_FALLOCATE)
 # AddressSanitizer conflicts with lib/Support/Unix/Signals.inc
-if( HAVE_SIGNAL_H AND NOT LLVM_USE_SANITIZER MATCHES ".*Address.*")
+# and backtraces do not work on Apple platforms when using sigaltstack.
+if( HAVE_SIGNAL_H AND NOT LLVM_USE_SANITIZER MATCHES ".*Address.*" AND NOT APPLE )
   check_symbol_exists(sigaltstack signal.h HAVE_SIGALTSTACK)
 endif()
 if( HAVE_SYS_UIO_H )