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Add Stephan's "Very bad HACK" to the iOS code, too, for iOS 14

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Change-Id: Ie05d2dc77bfdcd323037d2e94b523808df4e1c9c
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/102916
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Tor Lillqvist <tml@collabora.com>
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/102980
Tested-by: Tor Lillqvist <tml@collabora.com>
This commit is contained in:
Tor Lillqvist
2020-09-17 14:02:24 +03:00
parent d4105c8aec
commit dba1a27be2
2 changed files with 42 additions and 1 deletions
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26
bridges/source/cpp_uno/gcc3_ios/except.cxx
View File

@@ -351,6 +351,32 @@ void fillUnoException(uno_Any * pUnoExc, uno_Mapping * pCpp2Uno)
return;
}
// Very bad HACK to find out whether we run against a libcxxabi that has a new
// __cxa_exception::reserved member at the start, introduced with LLVM 10
// <https://github.com/llvm/llvm-project/commit/674ec1eb16678b8addc02a4b0534ab383d22fa77>
// "[libcxxabi] Insert padding in __cxa_exception struct for compatibility". The layout of the
// start of __cxa_exception is
//
// [8 byte void *reserve]
// 8 byte size_t referenceCount
//
// where the (bad, hacky) assumption is that reserve (if present) is null
// (__cxa_allocate_exception in at least LLVM 11 zero-fills the object, and nothing actively
// sets reserve) while referenceCount is non-null (__cxa_throw sets it to 1, and
// __cxa_decrement_exception_refcount destroys the exception as soon as it drops to 0; for a
// __cxa_dependent_exception, the referenceCount member is rather
//
// 8 byte void* primaryException
//
// but which also will always be set to a non-null value in __cxa_rethrow_primary_exception).
// As described in the definition of __cxa_exception
// (bridges/source/cpp_uno/gcc3_macosx_x86-64/share.hxx), this hack (together with the "#if 0"
// there) can be dropped once we can be sure that we only run against new libcxxabi that has the
// reserve member:
if (*reinterpret_cast<void **>(header) == nullptr) {
header = reinterpret_cast<__cxa_exception *>(reinterpret_cast<void **>(header) + 1);
}
std::type_info *exceptionType = __cxxabiv1::__cxa_current_exception_type();
typelib_TypeDescription * pExcTypeDescr = nullptr;

17
bridges/source/cpp_uno/gcc3_ios/unwind-cxx.h
View File

@@ -59,8 +59,23 @@ namespace __cxxabiv1
// followed by the exception object itself.
struct __cxa_exception
{
{
#if __LP64__
#if 0
// This is a new field added with LLVM 10
// <https://github.com/llvm/llvm-project/commit/674ec1eb16678b8addc02a4b0534ab383d22fa77>
// "[libcxxabi] Insert padding in __cxa_exception struct for compatibility". The HACK in
// fillUnoException (bridges/source/cpp_uno/gcc3_macosx_x86-64/except.cxx) tries to find out at
// runtime whether a __cxa_exception has this member. Once we can be sure that we only run
// against new libcxxabi that has this member, we can drop the "#if 0" here and drop the hack
// in fillUnoException.
// Now _Unwind_Exception is marked with __attribute__((aligned)),
// which implies __cxa_exception is also aligned. Insert padding
// in the beginning of the struct, rather than before unwindHeader.
void *reserve;
#endif
// This is a new field to support C++ 0x exception_ptr.
// For binary compatibility it is at the start of this
// struct which is prepended to the object thrown in