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author | Akira Hatanaka <ahatanaka@apple.com> | 2017-05-13 03:14:49 +0000 |
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committer | Akira Hatanaka <ahatanaka@apple.com> | 2017-05-13 03:14:49 +0000 |
commit | c501f754a584701bbe1646a2a16bcdc8aabae9ea (patch) | |
tree | 7fce143cd9c03566f1a1bbab15c5e8e16a1d0fcb /libcxxabi | |
parent | 5057086a35a6116a65c6ee1da5be09e65ac5ba8a (diff) | |
download | llvm-c501f754a584701bbe1646a2a16bcdc8aabae9ea.zip llvm-c501f754a584701bbe1646a2a16bcdc8aabae9ea.tar.gz llvm-c501f754a584701bbe1646a2a16bcdc8aabae9ea.tar.bz2 |
[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
llvm-svn: 302978
Diffstat (limited to 'libcxxabi')
-rw-r--r-- | libcxxabi/src/cxa_exception.hpp | 12 | ||||
-rw-r--r-- | libcxxabi/test/exception_object_alignment.sh.cpp | 48 |
2 files changed, 58 insertions, 2 deletions
diff --git a/libcxxabi/src/cxa_exception.hpp b/libcxxabi/src/cxa_exception.hpp index c009db4..2d34698 100644 --- a/libcxxabi/src/cxa_exception.hpp +++ b/libcxxabi/src/cxa_exception.hpp @@ -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_exception { 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 { diff --git a/libcxxabi/test/exception_object_alignment.sh.cpp b/libcxxabi/test/exception_object_alignment.sh.cpp new file mode 100644 index 0000000..5f4aea2 --- /dev/null +++ b/libcxxabi/test/exception_object_alignment.sh.cpp @@ -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; +} |