From 19f802ff68361af0a28c8ad6e12daf9bd740b96d Mon Sep 17 00:00:00 2001 From: Eric Fiselier Date: Wed, 20 Jul 2016 23:56:42 +0000 Subject: [PATCH] [libunwind] Properly align _Unwind_Exception. Summary: _Unwind_Exception is required to be double word aligned. Currently the struct is under aligned. Reviewers: mclow.lists, compnerd, kledzik, emaste Subscribers: emaste, cfe-commits Differential Revision: https://reviews.llvm.org/D22543 llvm-svn: 276215 --- libunwind/include/unwind.h | 9 ++++++--- libunwind/test/alignment.pass.cpp | 21 +++++++++++++++++++++ 2 files changed, 27 insertions(+), 3 deletions(-) create mode 100644 libunwind/test/alignment.pass.cpp diff --git a/libunwind/include/unwind.h b/libunwind/include/unwind.h index 8f0ef92..0e01a2c 100644 --- a/libunwind/include/unwind.h +++ b/libunwind/include/unwind.h @@ -122,13 +122,16 @@ struct _Unwind_Exception { uintptr_t private_1; // non-zero means forced unwind uintptr_t private_2; // holds sp that phase1 found for phase2 to use #ifndef __LP64__ - // The gcc implementation of _Unwind_Exception used attribute mode on the - // above fields which had the side effect of causing this whole struct to + // The implementation of _Unwind_Exception uses an attribute mode on the + // above fields which has the side effect of causing this whole struct to // round up to 32 bytes in size. To be more explicit, we add pad fields // added for binary compatibility. uint32_t reserved[3]; #endif -}; + // The Itanium ABI requires that _Unwind_Exception objects are "double-word + // aligned". GCC has interpreted this to mean "use the maximum useful + // alignment for the target"; so do we. +} __attribute__((__aligned__)); typedef _Unwind_Reason_Code (*_Unwind_Stop_Fn) (int version, diff --git a/libunwind/test/alignment.pass.cpp b/libunwind/test/alignment.pass.cpp new file mode 100644 index 0000000..5ab5584 --- /dev/null +++ b/libunwind/test/alignment.pass.cpp @@ -0,0 +1,21 @@ +// -*- C++ -*- +//===----------------------------------------------------------------------===// +// +// 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. +// +//===----------------------------------------------------------------------===// + +// The Itanium ABI requires that _Unwind_Exception objects are "double-word +// aligned". + +#include + +struct MaxAligned {} __attribute__((aligned)); +static_assert(alignof(_Unwind_Exception) == alignof(MaxAligned), ""); + +int main() +{ +} -- 2.7.4