https://github.com/a-tarasyuk updated
https://github.com/llvm/llvm-project/pull/101853
>From befd46e0c2d3244941e4c4d48dd03d4edb3d4c04 Mon Sep 17 00:00:00 2001
From: Oleksandr T <oleksandr.taras...@outlook.com>
Date: Sun, 4 Aug 2024 00:45:49 +0300
Subject: [PATCH] [Clang] strengthen checks for 'main' function to meet
[basic.start.main] p3 requirements
---
clang/docs/ReleaseNotes.rst | 2 +
.../clang/Basic/DiagnosticSemaKinds.td | 6 ++
clang/lib/AST/Decl.cpp | 8 +--
clang/lib/Sema/SemaDecl.cpp | 30 +++++++--
.../basic/basic.start/basic.start.main/p3.cpp | 61 +++++++++++++++++++
5 files changed, 96 insertions(+), 11 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 4c7bd099420ab..93eec78606301 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -145,6 +145,8 @@ Improvements to Clang's diagnostics
- -Wdangling-assignment-gsl is enabled by default.
+- Clang now diagnoses the use of `main` in an `extern "C"` context as invalid
according to [basic.start.main] p3. Fixes #GH101512.
+
Improvements to Clang's time-trace
----------------------------------
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td
b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 581434d33c5c9..21a66ea04704c 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -990,6 +990,12 @@ def warn_main_redefined : Warning<"variable named 'main'
with external linkage "
"has undefined behavior">, InGroup<Main>;
def ext_main_used : Extension<
"referring to 'main' within an expression is a Clang extension">,
InGroup<Main>;
+def ext_main_invalid_linkage_specification : ExtWarn<
+ "'main' should not be "
+ "'extern \"%select{C|C++}0\"'">, InGroup<Main>;
+def err_main_invalid_linkage_specification : Error<
+ "'main' should not be "
+ "'extern \"%select{C|C++}0\"'">;
/// parser diagnostics
def ext_no_declarators : ExtWarn<"declaration does not declare anything">,
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 490c4a2fc525c..9bf2ee680073b 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -3292,11 +3292,9 @@ bool FunctionDecl::isImmediateFunction() const {
}
bool FunctionDecl::isMain() const {
- const TranslationUnitDecl *tunit =
- dyn_cast<TranslationUnitDecl>(getDeclContext()->getRedeclContext());
- return tunit &&
- !tunit->getASTContext().getLangOpts().Freestanding &&
- isNamed(this, "main");
+ const DeclContext *DC = getDeclContext();
+ return isNamed(this, "main") && !getLangOpts().Freestanding &&
+ (DC->getRedeclContext()->isTranslationUnit() || isExternC());
}
bool FunctionDecl::isMSVCRTEntryPoint() const {
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 4fea38d1b02a9..8c3b130515c6e 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -7353,6 +7353,14 @@ void emitReadOnlyPlacementAttrWarning(Sema &S, const
VarDecl *VD) {
}
}
+static bool isMainVar(DeclarationName Name, VarDecl *VD) {
+ return Name.getAsIdentifierInfo() &&
+ Name.getAsIdentifierInfo()->isStr("main") &&
+ !VD->getDescribedVarTemplate() &&
+ (VD->getDeclContext()->getRedeclContext()->isTranslationUnit() ||
+ VD->isExternC());
+}
+
NamedDecl *Sema::ActOnVariableDeclarator(
Scope *S, Declarator &D, DeclContext *DC, TypeSourceInfo *TInfo,
LookupResult &Previous, MultiTemplateParamsArg TemplateParamLists,
@@ -8052,10 +8060,7 @@ NamedDecl *Sema::ActOnVariableDeclarator(
}
// Special handling of variable named 'main'.
- if (Name.getAsIdentifierInfo() && Name.getAsIdentifierInfo()->isStr("main")
&&
- NewVD->getDeclContext()->getRedeclContext()->isTranslationUnit() &&
- !getLangOpts().Freestanding && !NewVD->getDescribedVarTemplate()) {
-
+ if (!getLangOpts().Freestanding && isMainVar(Name, NewVD)) {
// C++ [basic.start.main]p3
// A program that declares a variable main at global scope is ill-formed.
if (getLangOpts().CPlusPlus)
@@ -12210,7 +12215,21 @@ bool Sema::CheckFunctionDeclaration(Scope *S,
FunctionDecl *NewFD,
return Redeclaration;
}
-void Sema::CheckMain(FunctionDecl* FD, const DeclSpec& DS) {
+void Sema::CheckMain(FunctionDecl *FD, const DeclSpec &DS) {
+ // [basic.start.main]p3
+ // The main function shall not be declared with a linkage-specification.
+ if ((FD->isExternCContext() || FD->isExternCXXContext())) {
+ unsigned DiagID = 0;
+ if (FD->getDeclContext()->getRedeclContext()->isTranslationUnit())
+ DiagID = diag::ext_main_invalid_linkage_specification;
+ else if (FD->isExternCContext())
+ DiagID = diag::err_main_invalid_linkage_specification;
+
+ if (DiagID)
+ Diag(FD->getLocation(), DiagID) << FD->getLanguageLinkage();
+ FD->setInvalidDecl();
+ return;
+ }
// C++11 [basic.start.main]p3:
// A program that [...] declares main to be inline, static or
// constexpr is ill-formed.
@@ -12238,7 +12257,6 @@ void Sema::CheckMain(FunctionDecl* FD, const DeclSpec&
DS) {
<< FixItHint::CreateRemoval(DS.getConstexprSpecLoc());
FD->setConstexprKind(ConstexprSpecKind::Unspecified);
}
-
if (getLangOpts().OpenCL) {
Diag(FD->getLocation(), diag::err_opencl_no_main)
<< FD->hasAttr<OpenCLKernelAttr>();
diff --git a/clang/test/CXX/basic/basic.start/basic.start.main/p3.cpp
b/clang/test/CXX/basic/basic.start/basic.start.main/p3.cpp
index f7085ca31d6c9..6d8d7c7a35963 100644
--- a/clang/test/CXX/basic/basic.start/basic.start.main/p3.cpp
+++ b/clang/test/CXX/basic/basic.start/basic.start.main/p3.cpp
@@ -8,6 +8,9 @@
// RUN: %clang_cc1 -fsyntax-only -verify %s -DTEST8
// RUN: %clang_cc1 -fsyntax-only -verify %s -DTEST9
// RUN: %clang_cc1 -fsyntax-only -verify %s -DTEST10 -ffreestanding
+// RUN: %clang_cc1 -fsyntax-only -verify %s -DTEST11
+// RUN: %clang_cc1 -fsyntax-only -verify %s -DTEST12
+// RUN: %clang_cc1 -fsyntax-only -verify -pedantic-errors %s -DTEST13
#if TEST1
int main; // expected-error{{main cannot be declared as global variable}}
@@ -61,6 +64,64 @@ int q(void)
// expected-no-diagnostics
int main;
+#elif TEST11
+extern "C" {
+ namespace Y {
+ int main; // expected-error {{main cannot be declared as global variable}}
+ }
+}
+namespace ns {
+ extern "C" int main; // expected-error {{main cannot be declared as global
variable}}
+}
+
+#elif TEST12
+extern "C" struct A { int main(); }; // ok
+
+namespace c {
+ extern "C" void main(); // expected-error {{'main' should not be 'extern
"C"'}}
+}
+
+extern "C" {
+ namespace Z {
+ void main(); // expected-error {{'main' should not be 'extern "C"'}}
+ }
+}
+
+namespace ns {
+ extern "C" struct A {
+ int main; // ok
+ };
+
+ extern "C" struct B {
+ int main(); // ok
+ };
+}
+
+#elif TEST13
+extern "C++" {
+ int main(); // expected-error {{'main' should not be 'extern "C++"'}}
+}
+
+extern "C" {
+ int main(); // expected-error {{'main' should not be 'extern "C"'}}
+}
+
+extern "C" int main(); // expected-error {{'main' should not be 'extern "C"'}}
+extern "C++" int main(); // expected-error {{'main' should not be 'extern
"C++"'}}
+
+namespace ns1 {
+ extern "C++" int main(); // ok
+ extern "C" {
+ extern "C++" {
+ int main(void *); // ok
+ }
+ }
+}
+
+namespace ns2 {
+ extern "C++" void main() {} // ok
+}
+
#else
#error Unknown Test
#endif
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
