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Merge libcxxrt commit 45ca8b1942090226ba9368caeeeabc0d4ee41ad6

Description

Merge libcxxrt commit 45ca8b1942090226ba9368caeeeabc0d4ee41ad6

Insert padding in __cxa_exception struct for compatibility

Similar to https://github.com/llvm/llvm-project/commit/f2a436058fcb, the
addition of __attribute__((__aligned__)) to _Unwind_Exception (in commit
b9616964) causes implicit padding to be inserted before the unwindHeader
field in __cxa_exception.

Applications attempt to get at the earlier fields in __cxa_exception, so
preserve the same negative offsets in __cxa_exception, by moving the
padding to the beginning of the struct.

The assumption here is that if the ABI is not aware of the padding
before unwindHeader and put the referenceCount/primaryException in
there, no padding should exist before unwindHeader.

This should make libreoffice's custom exception handling mechanisms work
correctly, even if it was built against an older cxxabi.h/unwind.h pair.

PR: 263370
Approved by: re (gjb, early MFC)
MFC after: immediately

(cherry picked from commit 434215c26da3c6acf2423ab93ff2b41b2d823cc8)

Details

Provenance
dimAuthored on Apr 19 2022, 4:11 PM
Parents
rG37c9ff4adfbd: Fix a sign mismatch warning in the physmem code
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