================ @@ -49,7 +48,24 @@ #define __need_rsize_t #endif #define __need_wchar_t +#if !defined(__STDDEF_H) || __has_feature(modules) +/* + * __stddef_null.h is special when building without modules: if __need_NULL is + * set, then it will unconditionally redefine NULL. To avoid stepping on client + * definitions of NULL, __need_NULL should only be set the first time this + * header is included, that is when __STDDEF_H is not defined. However, when + * building with modules, this header is a textual header and needs to + * unconditionally include __stdef_null.h to support multiple submodules + * exporting _Builtin_stddef.null. Take module SM with submodules A and B, whose + * headers both include stddef.h When SM.A builds, __STDDEF_H will be defined. + * When SM.B builds, the definition from SM.A will leak when building without + * local submodule visibility. stddef.h wouldn't include __stddef_null.h, and + * SM.B wouldn't import _Builtin_stddef.null, and SM.B's `export *` wouldn't + * export NULL as expected. When building with modules, always include + * __stddef_null.h so that everything works as expected. + */ #define __need_NULL +#endif ---------------- ian-twilightcoder wrote:
> we build __stddef_null.h as a modular header, even though it's really not > (it's supposed to redefine NULL each time it's included) But it _has_ to be a modular header because otherwise all the includers would declare `NULL` in their pcm so we'd have A.NULL, B.NULL, etc. Though I don't think you generally use `NULL` in Swift, if you somehow did (like `func doSomething(pointer: <something>? = NULL)` maybe?) that would cause problems. https://github.com/llvm/llvm-project/pull/99727 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
