在 2019/3/1 15:14, Ruslan Garipov 写道: >> It looks like we have ended up in a bug there > > I don't know :-( To summarize: MSVC, Intel C++ and GCC on Microsoft > Windows fail to compile that sample C code. But clang for Microsoft > Windows does compile the code (just like GCC for Linux-based OSes). > clang-cl fails to compile of course; due to the back-end shared with > MSVC I believe. >
This can be verified by printing the size of the enclosing struct using GCC with our header, then comparing it with the result using MSVC and Microsoft header. >> I think we should try promoting named nested structs and unions (so >> they appear in the file scope). At least this works for both C and >> C++, providing these names don't conflict with each other. > > If I understand you correctly, you propose to move declarations of the > nested structures like `_Time2Val`, `_DateTimeVal` and so on out of > declaration of the `SSVARIANT` structure (where they will be at the file > scope)? For both C and C++. > > I've also proposed the same thing but for C only, because such moving > out does not change senantics. Had I compiled the code with nested > structures successfully by a C compiler, the nested structures are at > unit scope I believe: > Yes. This results in consistent code, and doesn't bring duplication of the struct definition (outside the struct for C and inside it for C++). >> 6.7.2.1 Structure and union specifiers >> 8 The presence of a struct-declaration-list in a >> struct-or-union-specifier declares a new type, within a translation unit. > > But for C++ to preserve† isolation of the nested types (as it is in the > original header file) we may stick with a fix I've already shown -- a > fix proposed by you, Hao (declaring structure types before an anonymous > union having members of those types). > > Therefore, I want to use `#ifdef __cplusplus` to separate these two > solutions. > > † 10.3.10 Nested class declarations [class.nest] > 1 ... The name of a nested class is local to its enclosing class. The > nested class is in the scope of its enclosing class. > > It would result in duplicated definitions which I think is pretty bad. -- Best regards, LH_Mouse
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