diff options
| author | Akira Hatanaka <ahatanaka@apple.com> | 2017-05-16 15:19:08 +0000 |
|---|---|---|
| committer | Akira Hatanaka <ahatanaka@apple.com> | 2017-05-16 15:19:08 +0000 |
| commit | 1089e7519494be608611df538b5d17ebf246304c (patch) | |
| tree | f299138be1d3f26b178e3b23c65a4dd1404a1c08 /src | |
| parent | fa4e00b737b2c91a3f4e7b676ee196792e06b3af (diff) | |
[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 r302978 and r302981, which were reverted in r303016
because a libcxx test was failing on an AArch64 bot. I also modified the
libcxxabi test case to check the alignment of the pointer returned by
__cxa_allocate_exception rather than compiling the test with -O1 and
checking whether it segfaults.
rdar://problem/25364625
Differential Revision: https://reviews.llvm.org/D33030
git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@303175 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'src')
| -rw-r--r-- | src/cxa_exception.hpp | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/src/cxa_exception.hpp b/src/cxa_exception.hpp index c009db4..b9f74e3 100644 --- a/src/cxa_exception.hpp +++ b/src/cxa_exception.hpp @@ -61,7 +61,21 @@ struct _LIBCXXABI_HIDDEN __cxa_exception { size_t referenceCount; #endif + // 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 in unwind.h 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. + // + // For ARM EHABI, we do not align this field since _Unwind_Exception is an + // alias of _Unwind_Control_Block, which is not annotated with + // __attribute__((aligned). +#if defined(_LIBCXXABI_ARM_EHABI) _Unwind_Exception unwindHeader; +#else + _Unwind_Exception unwindHeader __attribute__((aligned)); +#endif }; // http://sourcery.mentor.com/archives/cxx-abi-dev/msg01924.html @@ -96,7 +110,13 @@ struct _LIBCXXABI_HIDDEN __cxa_dependent_exception { void* primaryException; #endif + // See the comment in __cxa_exception as to why this field has attribute + // aligned. +#if defined(_LIBCXXABI_ARM_EHABI) _Unwind_Exception unwindHeader; +#else + _Unwind_Exception unwindHeader __attribute__((aligned)); +#endif }; struct _LIBCXXABI_HIDDEN __cxa_eh_globals { |