diff options
| -rw-r--r-- | src/cxa_exception.hpp | 20 | ||||
| -rw-r--r-- | test/exception_object_alignment.pass.cpp | 33 |
2 files changed, 53 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 { diff --git a/test/exception_object_alignment.pass.cpp b/test/exception_object_alignment.pass.cpp new file mode 100644 index 0000000..addef18 --- /dev/null +++ b/test/exception_object_alignment.pass.cpp @@ -0,0 +1,33 @@ +//===---------------- exception_object_alignment.pass.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 + +// Check that the pointer __cxa_allocate_exception returns is aligned to the +// default alignment for the target architecture. + +#include <cassert> +#include <cstdint> +#include <cxxabi.h> +#include <type_traits> +#include <__cxxabi_config.h> + +struct S { + int a[4]; +} __attribute__((aligned)); + +int main() { +#if !defined(_LIBCXXABI_ARM_EHABI) + void *p = __cxxabiv1::__cxa_allocate_exception(16); + auto i = reinterpret_cast<uintptr_t>(p); + auto a = std::alignment_of<S>::value; + assert(i % a == 0); +#endif + return 0; +} |