bpo-36618: Add -fmax-type-align=8 flag for clang#12809
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vstinner merged 1 commit intopython:masterfrom Apr 12, 2019
vstinner:clang_align8
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bpo-36618: Add -fmax-type-align=8 flag for clang#12809vstinner merged 1 commit intopython:masterfrom vstinner:clang_align8
vstinner merged 1 commit intopython:masterfrom
vstinner:clang_align8
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Add -fmax-type-align=8 to CFLAGS when clang compiler is detected. The pymalloc memory allocator aligns memory on 8 bytes. On x86-64, clang expects alignment on 16 bytes by default and so uses MOVAPS instruction which can lead to segmentation fault. Instruct clang that Python is limited to alignemnt on 8 bytes to use MOVUPS instruction instead: slower but don't trigger a SIGSEGV if the memory is not aligned on 16 bytes. Sadly, the flag must be expected to CFLAGS and not just CFLAGS_NODIST, since third party C extensions can have the same issue.
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Add -fmax-type-align=8 to CFLAGS when clang compiler is detected.
The pymalloc memory allocator aligns memory on 8 bytes. On x86-64,
clang expects alignment on 16 bytes by default and so uses MOVAPS
instruction which can lead to segmentation fault. Instruct clang that
Python is limited to alignemnt on 8 bytes to use MOVUPS instruction
instead: slower but don't trigger a SIGSEGV if the memory is not
aligned on 16 bytes.
Sadly, the flag must be expected to CFLAGS and not just
CFLAGS_NODIST, since third party C extensions can have the same
issue.
https://bugs.python.org/issue36618