[libcxxabi] Add a test for invalid assumptions on the alignment of exceptions

rdar://problem/49864414

llvm-svn: 361039

Author: ldionne

libcxxabi/test/exception_object_alignment.2.pass.cpp

@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: libcxxabi-no-exceptions
+
+// This test checks that the compiler does not make incorrect assumptions
+// about the alignment of the exception (only in that specific case, of
+// course).
+//
+// There was a bug where Clang would emit a call to memset assuming a 16-byte
+// aligned exception even when back-deploying to older Darwin systems where
+// exceptions are 8-byte aligned, which caused a segfault on those systems.
+
+struct exception {
+    exception() : x(0) { }
+    virtual ~exception() { }
+    int x;
+};
+
+struct foo : exception { };
+
+int main() {
+    try {
+      throw foo();
+    } catch (...) {
+
+    }
+    return 0;
+}