llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-clang-driver Author: Ashwin Banwari (ashwinbanwari) <details> <summary>Changes</summary> Revival of https://github.com/llvm/llvm-project/pull/146247 which got reverted for broken test. Now that https://github.com/llvm/llvm-project/pull/146461 is merged to allow `extern "C++"` for main, we can merge this change. --- Full diff: https://github.com/llvm/llvm-project/pull/146635.diff 5 Files Affected: - (modified) clang/docs/ReleaseNotes.rst (+3) - (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+4) - (modified) clang/lib/Sema/SemaDecl.cpp (+8) - (modified) clang/test/Driver/autocomplete.c (+1) - (modified) clang/test/SemaCXX/modules.cppm (+2) ``````````diff diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 3d893e0aa8e2c..023f8ff7951d3 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -661,6 +661,9 @@ Improvements to Clang's diagnostics diagnostics when floating-point numbers had both width field and plus or space prefix specified. (#GH143951) +- A warning is now emitted when ``main`` is attached to a named module, + which can be turned off with ``-Wno-main-attached-to-named-module``. (#GH146247) + - Clang now avoids issuing `-Wreturn-type` warnings in some cases where the final statement of a non-void function is a `throw` expression, or a call to a function that is trivially known to always throw (i.e., its diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td index 6e48f3bc88bab..8a05b4b4af31b 100644 --- a/clang/include/clang/Basic/DiagnosticSemaKinds.td +++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td @@ -1062,6 +1062,10 @@ def err_constexpr_main : Error< "'main' is not allowed to be declared %select{constexpr|consteval}0">; def err_deleted_main : Error<"'main' is not allowed to be deleted">; def err_mainlike_template_decl : Error<"%0 cannot be a template">; +def warn_main_in_named_module + : ExtWarn<"'main' should not be attached to a named module; consider " + "adding C++ language linkage">, + InGroup<DiagGroup<"main-attached-to-named-module">>; def err_main_returns_nonint : Error<"'main' must return 'int'">; def ext_main_returns_nonint : ExtWarn<"return type of 'main' is not 'int'">, InGroup<MainReturnType>; diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp index 61b82b8377e22..de862e1ad8850 100644 --- a/clang/lib/Sema/SemaDecl.cpp +++ b/clang/lib/Sema/SemaDecl.cpp @@ -12486,6 +12486,14 @@ void Sema::CheckMain(FunctionDecl *FD, const DeclSpec &DS) { : FixItHint()); FD->setInvalidDecl(true); } + + // In C++ [basic.start.main]p3, it is said a program attaching main to a + // named module is ill-formed. + if (FD->isInNamedModule()) { + const SourceLocation start = FD->getTypeSpecStartLoc(); + Diag(start, diag::warn_main_in_named_module) + << FixItHint::CreateInsertion(start, "extern \"C++\" ", true); + } } // Treat protoless main() as nullary. diff --git a/clang/test/Driver/autocomplete.c b/clang/test/Driver/autocomplete.c index 8cc604dbff875..4983b71496834 100644 --- a/clang/test/Driver/autocomplete.c +++ b/clang/test/Driver/autocomplete.c @@ -111,6 +111,7 @@ // RUN: %clang --autocomplete=-Wma | FileCheck %s -check-prefix=WARNING // WARNING: -Wmacro-redefined // WARNING-NEXT: -Wmain +// WARNING-NEXT: -Wmain-attached-to-named-module // WARNING-NEXT: -Wmain-return-type // WARNING-NEXT: -Wmalformed-warning-check // WARNING-NEXT: -Wmany-braces-around-scalar-init diff --git a/clang/test/SemaCXX/modules.cppm b/clang/test/SemaCXX/modules.cppm index ddbbc7cd86360..5e0b3be9870c7 100644 --- a/clang/test/SemaCXX/modules.cppm +++ b/clang/test/SemaCXX/modules.cppm @@ -41,6 +41,8 @@ struct S { export static int n; // expected-error {{expected member name or ';'}} }; +int main() {} // expected-warning {{'main' should not be attached to a named module; consider adding C++ language linkage}} + // FIXME: Exports of declarations without external linkage are disallowed. // Exports of declarations with non-external-linkage types are disallowed. `````````` </details> https://github.com/llvm/llvm-project/pull/146635 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
