rjmccall added a comment. 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, 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
