[clang] 8a5b97a - Revert "[clang] [modules] Add err_main_in_named_module (#146247)"

[Chuanqi Xu via cfe-commits]

Author: Chuanqi Xu
Date: 2025-06-30T23:22:31+08:00
New Revision: 8a5b97a7205db189ca82f44dec7a399c2b5da546

URL: https://github.com/llvm/llvm-project/commit/8a5b97a7205db189ca82f44dec7a399c2b5da546
DIFF: https://github.com/llvm/llvm-project/commit/8a5b97a7205db189ca82f44dec7a399c2b5da546.diff

LOG: Revert "[clang] [modules] Add err_main_in_named_module (#146247)"

This reverts commit 473769ec9b2f860813229eb449fb4298dfc7ff94.

It breaks test in libc++

See https://github.com/llvm/llvm-project/pull/146247

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/include/clang/Basic/DiagnosticSemaKinds.td
    clang/lib/Sema/SemaDecl.cpp
    clang/test/Driver/autocomplete.c
    clang/test/SemaCXX/modules.cppm

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index f13d99845ee9a..d3e7ea0e73219 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -655,9 +655,6 @@ Improvements to Clang's diagnostics
   #GH69470, #GH59391, #GH58172, #GH46215, #GH45915, #GH45891, #GH44490,
   #GH36703, #GH32903, #GH23312, #GH69874.
 
-- 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 451619709c087..5062505cf3c01 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1062,10 +1062,6 @@ 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 f4bc191d1dae6..a34e2c9cbb003 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -12489,14 +12489,6 @@ 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 4983b71496834..8cc604dbff875 100644
--- a/clang/test/Driver/autocomplete.c
+++ b/clang/test/Driver/autocomplete.c
@@ -111,7 +111,6 @@
 // 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 81bc749c58259..5d0d6da44a2ed 100644
--- a/clang/test/SemaCXX/modules.cppm
+++ b/clang/test/SemaCXX/modules.cppm
@@ -68,8 +68,6 @@ int n;
 //--- test3.cpp
 export module bar;
 
-int main() {} // expected-warning {{'main' should not be attached to a named module; consider adding C++ language linkage}}
-
 static int m;
 
 int n;