BUG: Fix -fsanitize=alignment issue in numpy/_core/src/multiarray/arraytypes.c.src #25136
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…es.c.src OBJECT_nonzero may be called with misaligned pointers, manifesting as a -fsanitize=alignment failure. This is UB per C11 6.3.2.3 > A pointer to an object type may be converted to a pointer to a different object type. If the resulting pointer is not correctly aligned) for the referenced type, the behavior is undefined. Nevertheless, Clang only checks alignment when the unaligned pointer is accessed. https://lists.llvm.org/pipermail/llvm-dev/2016-January/094012.html Call memcpy with unaligned arguments instead to work with new Clang (llvm/llvm-project#67766).
seberg
approved these changes
Nov 13, 2023
| @@ -2856,7 +2856,7 @@ OBJECT_nonzero (PyObject **ip, PyArrayObject *ap) | |||
| } | |||
| else { | |||
| PyObject *obj; | |||
| memcpy(&obj, ip, sizeof(obj)); | |||
| memcpy(&obj, (void *)ip, sizeof(obj)); | |||
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Technically, it would be nicer to change top to char ** (or void ** I guess, but char is more common in NumPy, since it works well with strided loops).
charris
changed the title
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OBJECT_nonzero may be called with misaligned pointers, manifesting as a -fsanitize=alignment failure. This is UB per C11 6.3.2.3
Nevertheless, Clang only checks alignment when the unaligned pointer is accessed. https://lists.llvm.org/pipermail/llvm-dev/2016-January/094012.html Call memcpy with unaligned arguments instead to work with new Clang (llvm/llvm-project#67766).
Change originally by @MaskRay