New submission from Benjamin Peterson: 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. ---------- components: Interpreter Core files: alignment.patch keywords: patch messages: 274688 nosy: benjamin.peterson priority: normal severity: normal status: open title: obmalloc's 8-byte alignment causes undefined behavior type: behavior versions: Python 2.7, Python 3.3, Python 3.4, Python 3.5, Python 3.6, Python 3.7 Added file: http://bugs.python.org/file44413/alignment.patch _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue27987> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com