Author: ahatanak Date: Fri May 12 22:14:49 2017 New Revision: 302978 URL: http://llvm.org/viewvc/llvm-project?rev=302978&view=rev Log: [libcxxabi] Align unwindHeader on a double-word boundary.
r276215 made a change to annotate _Unwind_Exception with attribute "aligned" so that an exception object following field __cxa_exception is sufficiently aligned. This fix hasn't been incorporated to unwind.h on Darwin since it is an ABI breaking change. Instead of annotating struct _Unwind_Exception with the attribute, this commit annotates field unwindHeader of __cxa_exception. This ensures the exception object is sufficiently aligned without breaking the ABI. This recommits r302763 with fixes to RUN lines in the test case. rdar://problem/25364625 Differential Revision: https://reviews.llvm.org/D33030 Added: libcxxabi/trunk/test/exception_object_alignment.sh.cpp Modified: libcxxabi/trunk/src/cxa_exception.hpp Modified: libcxxabi/trunk/src/cxa_exception.hpp URL: http://llvm.org/viewvc/llvm-project/libcxxabi/trunk/src/cxa_exception.hpp?rev=302978&r1=302977&r2=302978&view=diff ============================================================================== --- libcxxabi/trunk/src/cxa_exception.hpp (original) +++ libcxxabi/trunk/src/cxa_exception.hpp Fri May 12 22:14:49 2017 @@ -61,7 +61,13 @@ struct _LIBCXXABI_HIDDEN __cxa_exception size_t referenceCount; #endif - _Unwind_Exception unwindHeader; + // This field is annotated with attribute aligned so that the exception + // object following the field is sufficiently aligned and there is no + // gap between the field and the exception object. r276215 made a change to + // annotate _Unwind_Exception with __attribute__((aligned)), but we cannot + // incorporate the fix on Darwin since it is an ABI-breaking change, which + // is why we need the attribute on this field. + _Unwind_Exception unwindHeader __attribute__((aligned)); }; // http://sourcery.mentor.com/archives/cxx-abi-dev/msg01924.html @@ -96,7 +102,9 @@ struct _LIBCXXABI_HIDDEN __cxa_dependent void* primaryException; #endif - _Unwind_Exception unwindHeader; + // See the comment in __cxa_exception as to why this field has attribute + // aligned. + _Unwind_Exception unwindHeader __attribute__((aligned)); }; struct _LIBCXXABI_HIDDEN __cxa_eh_globals { Added: libcxxabi/trunk/test/exception_object_alignment.sh.cpp URL: http://llvm.org/viewvc/llvm-project/libcxxabi/trunk/test/exception_object_alignment.sh.cpp?rev=302978&view=auto ============================================================================== --- libcxxabi/trunk/test/exception_object_alignment.sh.cpp (added) +++ libcxxabi/trunk/test/exception_object_alignment.sh.cpp Fri May 12 22:14:49 2017 @@ -0,0 +1,48 @@ +//===---------------- exception_object_alignment.sh.cpp -------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is dual licensed under the MIT and the University of Illinois Open +// Source Licenses. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + +// UNSUPPORTED: libcxxabi-no-exceptions + +// RUN: %build -O1 +// RUN: %run + +// This test used to fail on Darwin because field unwindHeader of struct +// __cxa_exception and the exception object that immediately followed were not +// 16B aligned. It would segfault in class derived's constructor when a movaps +// tried to write to a memory operand that was not 16B aligned. + +namespace { + +struct S { + int a; + int __attribute__((aligned(16))) b; +}; + +class base1 { +protected: + virtual ~base1() throw() {} +}; + +class derived: public base1 { +public: + derived() : member() {} +private: + S member; +}; + +} + +int main() { + try { + throw derived(); + } + catch(...) { + } + return 0; +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
