llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-clang Author: Ian Anderson (ian-twilightcoder) <details> <summary>Changes</summary> stddef.h always includes __stddef_null.h. This is fine in modules because it's not possible to re-include the pcm, and it's necessary to export the _Builtin_stddef.null submodule. However, without modules it causes NULL to always get redefined which disrupts some C++ code. Rework the inclusion of __stddef_null.h so that with not building with modules it's only included if __need_NULL is set by the includer, or it's the first time stddef.h is being included. --- Full diff: https://github.com/llvm/llvm-project/pull/99727.diff 3 Files Affected: - (modified) clang/lib/Headers/stdarg.h (+2-2) - (modified) clang/lib/Headers/stddef.h (+20-2) - (modified) clang/test/Headers/stddefneeds.cpp (+11-4) ``````````diff diff --git a/clang/lib/Headers/stdarg.h b/clang/lib/Headers/stdarg.h index 8292ab907becf..6203d7a600a23 100644 --- a/clang/lib/Headers/stdarg.h +++ b/clang/lib/Headers/stdarg.h @@ -20,19 +20,18 @@ * modules. */ #if defined(__MVS__) && __has_include_next(<stdarg.h>) -#include <__stdarg_header_macro.h> #undef __need___va_list #undef __need_va_list #undef __need_va_arg #undef __need___va_copy #undef __need_va_copy +#include <__stdarg_header_macro.h> #include_next <stdarg.h> #else #if !defined(__need___va_list) && !defined(__need_va_list) && \ !defined(__need_va_arg) && !defined(__need___va_copy) && \ !defined(__need_va_copy) -#include <__stdarg_header_macro.h> #define __need___va_list #define __need_va_list #define __need_va_arg @@ -45,6 +44,7 @@ !defined(__STRICT_ANSI__) #define __need_va_copy #endif +#include <__stdarg_header_macro.h> #endif #ifdef __need___va_list diff --git a/clang/lib/Headers/stddef.h b/clang/lib/Headers/stddef.h index 8985c526e8fc5..dab464805ccea 100644 --- a/clang/lib/Headers/stddef.h +++ b/clang/lib/Headers/stddef.h @@ -20,7 +20,6 @@ * modules. */ #if defined(__MVS__) && __has_include_next(<stddef.h>) -#include <__stddef_header_macro.h> #undef __need_ptrdiff_t #undef __need_size_t #undef __need_rsize_t @@ -31,6 +30,7 @@ #undef __need_max_align_t #undef __need_offsetof #undef __need_wint_t +#include <__stddef_header_macro.h> #include_next <stddef.h> #else @@ -40,7 +40,6 @@ !defined(__need_NULL) && !defined(__need_nullptr_t) && \ !defined(__need_unreachable) && !defined(__need_max_align_t) && \ !defined(__need_offsetof) && !defined(__need_wint_t) -#include <__stddef_header_macro.h> #define __need_ptrdiff_t #define __need_size_t /* ISO9899:2011 7.20 (C11 Annex K): Define rsize_t if __STDC_WANT_LIB_EXT1__ is @@ -49,7 +48,25 @@ #define __need_rsize_t #endif #define __need_wchar_t +#if !defined(__STDDEF_H) && !__building_module(_Builtin_stddef) +/* + * __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 any of its + * implementation headers, and SM.B wouldn't import any of the stddef modules, + * and SM.B's `export *` wouldn't export any stddef interfaces as expected. When + * building with modules, always include __stddef_null.h so that everything + * works as expected. + */ #define __need_NULL +#endif #if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L) || \ defined(__cplusplus) #define __need_nullptr_t @@ -65,6 +82,7 @@ /* wint_t is provided by <wchar.h> and not <stddef.h>. It's here * for compatibility, but must be explicitly requested. Therefore * __need_wint_t is intentionally not defined here. */ +#include <__stddef_header_macro.h> #endif #if defined(__need_ptrdiff_t) diff --git a/clang/test/Headers/stddefneeds.cpp b/clang/test/Headers/stddefneeds.cpp index 0763bbdee13ae..0282e8afa600d 100644 --- a/clang/test/Headers/stddefneeds.cpp +++ b/clang/test/Headers/stddefneeds.cpp @@ -56,14 +56,21 @@ max_align_t m5; #undef NULL #define NULL 0 -// glibc (and other) headers then define __need_NULL and rely on stddef.h -// to redefine NULL to the correct value again. -#define __need_NULL +// Including stddef.h again shouldn't redefine NULL #include <stddef.h> // gtk headers then use __attribute__((sentinel)), which doesn't work if NULL // is 0. -void f(const char* c, ...) __attribute__((sentinel)); +void f(const char* c, ...) __attribute__((sentinel)); // expected-note{{function has been explicitly marked sentinel here}} void g() { + f("", NULL); // expected-warning{{missing sentinel in function call}} +} + +// glibc (and other) headers then define __need_NULL and rely on stddef.h +// to redefine NULL to the correct value again. +#define __need_NULL +#include <stddef.h> + +void h() { f("", NULL); // Shouldn't warn. } `````````` </details> 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
