Author benjamin.peterson
Recipients benjamin.peterson
Date 2016-09-07.00:17:00
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Message-id <1473207430.19.0.578630759123.issue27987@psf.upfronthosting.co.za>
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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 User Action Args
2016-09-07 00:17:10benjamin.petersonsetrecipients: + benjamin.peterson
2016-09-07 00:17:10benjamin.petersonsetmessageid: <1473207430.19.0.578630759123.issue27987@psf.upfronthosting.co.za>
2016-09-07 00:17:09benjamin.petersonlinkissue27987 messages
2016-09-07 00:17:06benjamin.petersoncreate