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103 lines
4.8 KiB
103 lines
4.8 KiB
From 986bd28388df745dd969e7be7c3bda36b2b2cb0e Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Caol=C3=A1n=20McNamara?= <caolanm@redhat.com>
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Date: Thu, 6 Aug 2020 10:50:47 +0100
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Subject: [PATCH] ofz#24641 libc++abi __cxa_exception has grown another member
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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https: //github.com/llvm/llvm-project/commit/f2a436058fcbc11291e73badb44e243f61046183
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this is the same problem as
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commit f4b6f6a8ae60bdec53512728d00853b73fa18500
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Author: Stephan Bergmann <sbergman@redhat.com>
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Date: Thu Feb 13 08:40:11 2020 +0100
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Hack to dynamically adapt to __cxa_exceptiom in LLVM 11 libcxxabi
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(where the new change to __cxa_exception effectively reverts the change that
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prompted 7a9dd3d482deeeb3ed1d50074e56adbd3f928296 "Hack to dynamically adapt to
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__cxa_exceptiom in LLVM 5.0 libcxxabi")
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Change-Id: Iec4ef1dc188bea2223d99b1b7eb8adec636c98e7
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Reviewed-on: https://gerrit.libreoffice.org/c/core/+/88583
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Tested-by: Jenkins
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Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
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so c-n-p that solution here
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Change-Id: I4475757a766e3ade7b9fcaf6149e535c9f9a4fa4
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Reviewed-on: https://gerrit.libreoffice.org/c/core/+/100209
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Tested-by: Caolán McNamara <caolanm@redhat.com>
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Reviewed-by: Caolán McNamara <caolanm@redhat.com>
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---
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.../cpp_uno/gcc3_linux_x86-64/except.cxx | 28 +++++++++++++++++++
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.../cpp_uno/gcc3_linux_x86-64/share.hxx | 14 ++++++++++
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2 files changed, 42 insertions(+)
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diff --git a/bridges/source/cpp_uno/gcc3_linux_x86-64/except.cxx b/bridges/source/cpp_uno/gcc3_linux_x86-64/except.cxx
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index e9e861f1c210..25931671f7dc 100644
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--- a/bridges/source/cpp_uno/gcc3_linux_x86-64/except.cxx
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+++ b/bridges/source/cpp_uno/gcc3_linux_x86-64/except.cxx
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@@ -150,6 +150,34 @@ void fillUnoException(uno_Any * pUnoExc, uno_Mapping * pCpp2Uno)
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return;
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}
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+#if defined _LIBCPPABI_VERSION // detect libc++abi
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+ // Very bad HACK to find out whether we run against a libcxxabi that has a new
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+ // __cxa_exception::reserved member at the start, introduced with LLVM 11
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+ // <https://github.com/llvm/llvm-project/commit/f2a436058fcbc11291e73badb44e243f61046183>
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+ // "[libcxxabi] Insert padding in __cxa_exception struct for compatibility". The layout of the
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+ // start of __cxa_exception is
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+ //
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+ // [8 byte void *reserve]
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+ // 8 byte size_t referenceCount
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+ //
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+ // where the (bad, hacky) assumption is that reserve (if present) is null
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+ // (__cxa_allocate_exception in at least LLVM 11 zero-fills the object, and nothing actively
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+ // sets reserve) while referenceCount is non-null (__cxa_throw sets it to 1, and
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+ // __cxa_decrement_exception_refcount destroys the exception as soon as it drops to 0; for a
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+ // __cxa_dependent_exception, the referenceCount member is rather
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+ //
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+ // 8 byte void* primaryException
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+ //
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+ // but which also will always be set to a non-null value in __cxa_rethrow_primary_exception).
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+ // As described in the definition of __cxa_exception
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+ // (bridges/source/cpp_uno/gcc3_linux_x86-64/share.hxx), this hack (together with the "#if 0"
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+ // there) can be dropped once we can be sure that we only run against new libcxxabi that has the
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+ // reserve member:
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+ if (*reinterpret_cast<void **>(header) == nullptr) {
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+ header = reinterpret_cast<__cxxabiv1::__cxa_exception*>(reinterpret_cast<void **>(header) + 1);
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+ }
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+#endif
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+
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std::type_info *exceptionType = __cxxabiv1::__cxa_current_exception_type();
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typelib_TypeDescription * pExcTypeDescr = nullptr;
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diff --git a/bridges/source/cpp_uno/gcc3_linux_x86-64/share.hxx b/bridges/source/cpp_uno/gcc3_linux_x86-64/share.hxx
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index e8afe35c4f59..53c8841fbbcb 100644
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--- a/bridges/source/cpp_uno/gcc3_linux_x86-64/share.hxx
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+++ b/bridges/source/cpp_uno/gcc3_linux_x86-64/share.hxx
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@@ -108,6 +108,20 @@ namespace __cxxabiv1 {
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struct __cxa_exception {
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#if defined _LIBCPPABI_VERSION // detect libc++abi
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#if defined __LP64__ || LIBCXXABI_ARM_EHABI
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+#if 0
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+ // This is a new field added with LLVM 11
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+ // <https://github.com/llvm/llvm-project/commit/f2a436058fcbc11291e73badb44e243f61046183>
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+ // "[libcxxabi] Insert padding in __cxa_exception struct for compatibility". The HACK in
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+ // fillUnoException (bridges/source/cpp_uno/gcc3_linux_x86-64/except.cxx) tries to find out at
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+ // runtime whether a __cxa_exception has this member. Once we can be sure that we only run
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+ // against new libcxxabi that has this member, we can drop the "#if 0" here and drop the hack
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+ // in fillUnoException.
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+
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+ // Now _Unwind_Exception is marked with __attribute__((aligned)),
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+ // which implies __cxa_exception is also aligned. Insert padding
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+ // in the beginning of the struct, rather than before unwindHeader.
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+ void *reserve;
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+#endif
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std::size_t referenceCount;
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#endif
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#endif
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