Naghasan added a comment. In D114080#3137480 <https://reviews.llvm.org/D114080#3137480>, @aaron.ballman wrote:
> In D114080#3137462 <https://reviews.llvm.org/D114080#3137462>, @Naghasan > wrote: > >> right, TIL `sizeof (ContainsArr)` is 0 according to clang. I can see trouble >> arising. >> >> @aaron.ballman maybe you know better, is that intended for the extension ? > > I don't *know*, but I have two educated guesses that it is intended. GCC > compatibility (GCC also has this behavior) and the relationship between > zero-sized array members and flexible array members. Clang allows a flexible > array member to be used in a structure with no members and it behaves the > same as a zero-sized array in a structure with no members: > https://godbolt.org/z/Gx7ozxYKz I see. I was confused as it normally C++ requires at least 1 byte. But I guess you need that for compatibility with C. In D114080#3137482 <https://reviews.llvm.org/D114080#3137482>, @Fznamznon wrote: > In D114080#3137430 <https://reviews.llvm.org/D114080#3137430>, @Naghasan > wrote: > >> Why the need for this restriction ? > > Zero length arrays are not supported by pure C++. It is an extension > supported by clang. They are also not allowed in OpenCL and SPIR-V, and I > even though I cannot grep an explicit restriction for them in SYCL 2020 spec > (I guess that is just because it is an extension and not pure C++) It doesn't > make sense to allow them here since memory allocation in device code is > prohibited in SYCL by the spec. This diagnostic prevents further not always > user friendly errors coming from SPIR-V emitters or from backends like OpenCL > that explicitly disallow them on early stage and in user-friendly form. I > believe other GPU programming models also may not allow them for the same > reason - restriction on memory allocation. SYCL won't mention this as it is an extension indeed. Same for VLA. SPIR-V is another question though, while 0 element array are not allowed, empty structs are (but IIRC size of an empty struct is not clear). > It doesn't make sense to allow them here since memory allocation in device > code is prohibited in SYCL by the spec I agree, but having a field defined is different from it being used. It is actually not uncommon to see SYCL functor passed with many unused fields (Eigen is good example). Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D114080/new/ https://reviews.llvm.org/D114080 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
