Use alignment builtins for ZEND_MM_ALIGNED macros#21913
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tobil4sk wants to merge 2 commits intophp:masterfrom
Open
Use alignment builtins for ZEND_MM_ALIGNED macros#21913tobil4sk wants to merge 2 commits intophp:masterfrom
tobil4sk wants to merge 2 commits intophp:masterfrom
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On some architectures, e.g. CHERI, pointers are wider than size_t so converting to size_t causes part of the pointer to be lost, which means it cannot be cast back into a pointer. It can be preserved by casting to uintptr_t instead.
Where available, these provide a more descriptive way of aligning pointers than direct bitwise manipulation. They are also more compatible with platforms like CHERI.
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Where available, these provide a more descriptive way of aligning pointers than direct bitwise manipulation. The additional abstraction they provide also makes them more compatible with platforms like CHERI.
Also, the non-builtin
ZEND_MM_ALIGNED_BASEimplementation now casts touintptr_tinstead ofsize_t, since the returned value tends to be used as a pointer, not a size. This makes intent clearer and also improves compatibility.These patches are from a port of PHP to pure-capability CHERI (where pointers are wider than
size_tand narrowing invalidates the pointer). Using these builtins improves compatibility generally and they seem preferable due to the abstraction. I thought I would send this patch upstream in case it is of interest.See: https://clang.llvm.org/docs/LanguageExtensions.html#alignment-builtins