Message274688
ubsan complains about unaligned access when structs include "long double". An example error:
runtime error: member access within misaligned address 0x7f77dbba9798 for type 'struct CDataObject', which requires 16 byte alignment
This is because (on x86 anyway), long double is 16-bytes long and requires that alignment, but obmalloc only gives a 8-byte alignment. (glibc malloc() gives 16-byte alignment.)
I'm attaching a POC patch. I don't know what the impact of increasing the alignment is on obmalloc's performance or memory usage. It's also unfortunate that this patch increases the size of PyGC_Head to 32 bytes from 24 bytes. One can imagine a more middle-ground solution to this by allowing types to specify their required alignment. |
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Date |
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2016-09-07 00:17:10 | benjamin.peterson | set | recipients:
+ benjamin.peterson |
2016-09-07 00:17:10 | benjamin.peterson | set | messageid: <1473207430.19.0.578630759123.issue27987@psf.upfronthosting.co.za> |
2016-09-07 00:17:09 | benjamin.peterson | link | issue27987 messages |
2016-09-07 00:17:06 | benjamin.peterson | create | |
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