Date: Sat, 20 Feb 2021 20:44:19 GMT From: Dimitry Andric <dim@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 780a76a6ec21 - stable/12 - Revert "Revert 3c4fd2463bb2 since upstream libcxxrt fixed it in another way" Message-ID: <202102202044.11KKiJUx058322@gitrepo.freebsd.org>
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The branch stable/12 has been updated by dim: URL: https://cgit.FreeBSD.org/src/commit/?id=780a76a6ec214cec0b8bc1f6b6c249984f5e24f5 commit 780a76a6ec214cec0b8bc1f6b6c249984f5e24f5 Author: Dimitry Andric <dim@FreeBSD.org> AuthorDate: 2021-02-20 20:40:41 +0000 Commit: Dimitry Andric <dim@FreeBSD.org> CommitDate: 2021-02-20 20:40:41 +0000 Revert "Revert 3c4fd2463bb2 since upstream libcxxrt fixed it in another way" This reverts commit 9e86d16697654c58ae65fd13e2a35fc755ecf73a, since I messed up and didn't merge the earlier libcxxrt changes first. --- contrib/libcxxrt/exception.cc | 30 ++++++++++++++++++++++++------ 1 file changed, 24 insertions(+), 6 deletions(-) diff --git a/contrib/libcxxrt/exception.cc b/contrib/libcxxrt/exception.cc index 0fb26ddb4ed2..0de878e9e6db 100644 --- a/contrib/libcxxrt/exception.cc +++ b/contrib/libcxxrt/exception.cc @@ -572,6 +572,19 @@ static void free_exception(char *e) } } +#ifdef __LP64__ +/** + * There's an ABI bug in __cxa_exception: unwindHeader requires 16-byte + * alignment but it was broken by the addition of the referenceCount. + * The unwindHeader is at offset 0x58 in __cxa_exception. In order to keep + * compatibility with consumers of the broken __cxa_exception, explicitly add + * padding on allocation (and account for it on free). + */ +static const int exception_alignment_padding = 8; +#else +static const int exception_alignment_padding = 0; +#endif + /** * Allocates an exception structure. Returns a pointer to the space that can * be used to store an object of thrown_size bytes. This function will use an @@ -580,16 +593,19 @@ static void free_exception(char *e) */ extern "C" void *__cxa_allocate_exception(size_t thrown_size) { - size_t size = thrown_size + sizeof(__cxa_exception); + size_t size = exception_alignment_padding + sizeof(__cxa_exception) + + thrown_size; char *buffer = alloc_or_die(size); - return buffer+sizeof(__cxa_exception); + return buffer + exception_alignment_padding + sizeof(__cxa_exception); } extern "C" void *__cxa_allocate_dependent_exception(void) { - size_t size = sizeof(__cxa_dependent_exception); + size_t size = exception_alignment_padding + + sizeof(__cxa_dependent_exception); char *buffer = alloc_or_die(size); - return buffer+sizeof(__cxa_dependent_exception); + return buffer + exception_alignment_padding + + sizeof(__cxa_dependent_exception); } /** @@ -617,7 +633,8 @@ extern "C" void __cxa_free_exception(void *thrown_exception) } } - free_exception(reinterpret_cast<char*>(ex)); + free_exception(reinterpret_cast<char*>(ex) - + exception_alignment_padding); } static void releaseException(__cxa_exception *exception) @@ -644,7 +661,8 @@ void __cxa_free_dependent_exception(void *thrown_exception) { releaseException(realExceptionFromException(reinterpret_cast<__cxa_exception*>(ex))); } - free_exception(reinterpret_cast<char*>(ex)); + free_exception(reinterpret_cast<char*>(ex) - + exception_alignment_padding); } /**
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