bridges/source/cpp_uno/gcc3_macosx_x86-64/except.cxx | 32 ++++++++++++++++++-
bridges/source/cpp_uno/gcc3_macosx_x86-64/share.hxx | 15 ++++++++
2 files changed, 46 insertions(+), 1 deletion(-)
New commits:
commit f4b6f6a8ae60bdec53512728d00853b73fa18500
Author: Stephan Bergmann <sberg...@redhat.com>
AuthorDate: Thu Feb 13 08:40:11 2020 +0100
Commit: Stephan Bergmann <sberg...@redhat.com>
CommitDate: Thu Feb 13 09:23:01 2020 +0100
Hack to dynamically adapt to __cxa_exceptiom in LLVM 11 libcxxabi
(where the new change to __cxa_exception effectively reverts the change that
prompted 7a9dd3d482deeeb3ed1d50074e56adbd3f928296 "Hack to dynamically
adapt to
__cxa_exceptiom in LLVM 5.0 libcxxabi")
Change-Id: Iec4ef1dc188bea2223d99b1b7eb8adec636c98e7
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/88583
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sberg...@redhat.com>
diff --git a/bridges/source/cpp_uno/gcc3_macosx_x86-64/except.cxx
b/bridges/source/cpp_uno/gcc3_macosx_x86-64/except.cxx
index c4cfe5123ec9..36eeda41bca7 100644
--- a/bridges/source/cpp_uno/gcc3_macosx_x86-64/except.cxx
+++ b/bridges/source/cpp_uno/gcc3_macosx_x86-64/except.cxx
@@ -274,7 +274,11 @@ static void deleteException( void * pExc )
// new libcxxabi is to look at the exceptionDestructor member, which must
// point to this function (the use of __cxa_exception in fillUnoException
is
// unaffected, as it only accesses members towards the start of the struct,
- // through a pointer known to actually point at the start):
+ // through a pointer known to actually point at the start). The libcxxabi
commit
+ //
<https://github.com/llvm/llvm-project/commit/f2a436058fcbc11291e73badb44e243f61046183>
+ // "[libcxxabi] Insert padding in __cxa_exception struct for
compatibility" towards LLVM 11
+ // removes the need for this hack, so it can be removed again once we can
be sure that we only
+ // run against libcxxabi from LLVM >= 11:
if (header->exceptionDestructor != &deleteException) {
header = reinterpret_cast<__cxa_exception const *>(
reinterpret_cast<char const *>(header) - 8);
@@ -348,6 +352,32 @@ 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 11
+ //
<https://github.com/llvm/llvm-project/commit/f2a436058fcbc11291e73badb44e243f61046183>
+ // "[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;
diff --git a/bridges/source/cpp_uno/gcc3_macosx_x86-64/share.hxx
b/bridges/source/cpp_uno/gcc3_macosx_x86-64/share.hxx
index 39939ab6be72..015cda1c00e5 100644
--- a/bridges/source/cpp_uno/gcc3_macosx_x86-64/share.hxx
+++ b/bridges/source/cpp_uno/gcc3_macosx_x86-64/share.hxx
@@ -68,6 +68,21 @@ typedef unsigned _Unwind_Ptr
__attribute__((__mode__(__pointer__)));
struct __cxa_exception
{
#if __LP64__
+#if 0
+ // This is a new field added with LLVM 11
+ //
<https://github.com/llvm/llvm-project/commit/f2a436058fcbc11291e73badb44e243f61046183>
+ // "[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
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