yihanaa added a comment. In D131979#3743127 <https://reviews.llvm.org/D131979#3743127>, @rjmccall wrote:
> In D131979#3742399 <https://reviews.llvm.org/D131979#3742399>, @yihanaa wrote: > >> As far as I know, turning on the -fsanitizer=alignment options when calling >> __builtin_assume_aligned in C code, if >> the 1st arg has volatile qualifier, Clang will emit "call void >> @__ubsan_handle_alignment_assumption(...)" in CodeGen, >> else Clang will emit an warning and ignore "call void >> @__ubsan_handle_alignment_assumption(...)". But the same situation in C++, >> Clang will generate an error in Sema. > > Honestly, that sounds like bad behavior, exactly what you'd get if Sema > naively tried to force a conversion to some specific pointer type like > `void*` instead of converting it to an r-value and then requiring it to have > pointer type. This is a fairly common bug for builtins that behave as if > they were overloaded; the fix is to give the builtin custom type-checking so > that it will work correctly with unusual qualifiers like address spaces and > `restrict`. I can walk you through that, but you can start by looking at > what `SemaBuiltinAtomicOverloaded` does for its pointer argument. > > If we want IRGen to not emit a check for pointers to `volatile`, that's an > easy check to do in IRGen if we set the AST up properly in the first place. > > John. > >> So I think, in order to keep this patch consistent with recent version of >> Clang and GCC behavior, when compile C code, Clang >> should not directly emit an error and exit in Sema, but should check the 1st >> arg's volatile qualifier in CodeGen and decide >> whether to emit "call void @__ubsan_handle_alignment_assumption(...)". >> >> But, I agree to use other ways to replace use getSubExprAsWritten() in >> CodeGen to check the 1st arg 'isVolatile', what do you all think about? >> >> For more information about UBSan, see >> https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html and search >> 'volatile' on this website. >> >> "The null, alignment, object-size, local-bounds, and vptr checks do not >> apply to pointers to types with the volatile qualifier." >> C https://godbolt.org/z/xv35fG14r >> C++ https://godbolt.org/z/qfje6sErE > > Honestly, I'm sorry I couldn't respond sooner. Thanks for your reply john, I agree with you, and I'd like to try it if we check args in Sema. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D131979/new/ https://reviews.llvm.org/D131979 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
