aaron.ballman added a comment. In https://reviews.llvm.org/D33826#866170, @lebedev.ri wrote:
> In https://reviews.llvm.org/D33826#866161, @JonasToth wrote: > > > There is an exception to the general rule (EXP36-C-EX2), stating that the > > result of `malloc` and friends is allowed to be casted to stricter > > alignments, since the pointer is known to be of correct alignment. > > > Quote for the reference: > > > EXP36-C-EX2: If a pointer is known to be correctly aligned to the target > > type, then a cast to that type is permitted. There are several cases where > > a pointer is known to be correctly aligned to the target type. The pointer > > could point to an object declared with a suitable alignment specifier. It > > could point to an object returned by aligned_alloc(), calloc(), malloc(), > > or realloc(), as per the C standard, section 7.22.3, paragraph 1 [ISO/IEC > > 9899:2011]. > > For plain `calloc(), malloc(), or realloc()`, i would guess it's related to > `max_align_t` / `std::max_align_t` / `__STDCPP_DEFAULT_NEW_ALIGNMENT__`, > which is generally just `16` bytes. It's a requirement from the C standard that malloc, calloc, and realloc return a suitably-aligned pointer for *any* type. >> Could you add a testcase for this case, i think there would currenlty be a >> false positive. >> >> And is there a general way of knowing when the pointer is of correct >> alignment, or is it necessary to keep a list of functions like `malloc` that >> are just known? >> If yes, i think it would be nice if this list is configurable (maybe like >> in cppcoreguidelines-no-malloc, where that functionality could be refactored >> out). Agreed, this should be a configurable list, but is should be pre-populated with the listed functions from the CERT standard. Repository: rL LLVM https://reviews.llvm.org/D33826 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
