On 12.02.2012 07:39, Chandler Carruth wrote:
On Sat, Feb 11, 2012 at 5:31 AM, Vasiliy Korchagin
<[email protected] <mailto:[email protected]>> wrote:
I agree, without setting implicit return zero bit changes in
codegen are not necessary. New version of patch is attached.
The warning you're adding, as David suggested, should be under a
separate flag.
It should also be an extwarn as this is technically a language
extension, and it should be enabled by default (you may already have
that, just want it clarified).
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -5795,8 +5795,13 @@ void Sema::CheckMain(FunctionDecl* FD, const
DeclSpec& DS) {
const FunctionType* FT = T->getAs<FunctionType>();
if (!Context.hasSameUnqualifiedType(FT->getResultType(),
Context.IntTy)) {
- Diag(FD->getTypeSpecStartLoc(), diag::err_main_returns_nonint);
- FD->setInvalidDecl(true);
+ if (getLangOptions().C99) {
+ // In C we allow main() to have non-integer return type.
+ Diag(FD->getTypeSpecStartLoc(), diag::warn_main_returns_nonint);
If you want this to be enabled in all C modes, you should accept more
than just C99: "!getLangOptions().CPlusPlus" is a good candidate here.
@@ -7204,7 +7209,8 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl,
Stmt *Body,
if (FD->isMain()) {
// C and C++ allow for main to automagically return 0.
// Implements C++ [basic.start.main]p5 and C99 5.1.2.2.3.
- FD->setHasImplicitReturnZero(true);
+ if (!getLangOptions().C99)
+ FD->setHasImplicitReturnZero(true);
This isn't correct. You need to be checking for a non-int return type
here, not for C99. If the function has an int return type we want the
implicit return zero.
Now new warning is under the separate flag ("-Wmain-return-type") and it
is an extwarn and it is enabled by default. Also problems with C modes
and implicit return zero are fixed. New patch is attached.
Vasiliy Korchagin,
The Institute for System Programming of the Russian Academy of Sciences
diff --git a/include/clang/Basic/DiagnosticGroups.td b/include/clang/Basic/DiagnosticGroups.td
index 4fa1982..3f73a67 100644
--- a/include/clang/Basic/DiagnosticGroups.td
+++ b/include/clang/Basic/DiagnosticGroups.td
@@ -104,6 +104,7 @@ def LocalTypeTemplateArgs : DiagGroup<"local-type-template-args",
[CXX98CompatLocalTypeTemplateArgs]>;
def MalformedWarningCheck : DiagGroup<"malformed-warning-check">;
def Main : DiagGroup<"main">;
+def MainReturnType : DiagGroup<"main-return-type">;
def MissingBraces : DiagGroup<"missing-braces">;
def MissingDeclarations: DiagGroup<"missing-declarations">;
def : DiagGroup<"missing-format-attribute">;
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index c35968c..5e5f100 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -348,6 +348,8 @@ def err_constexpr_main : Error<
"'main' is not allowed to be declared constexpr">;
def err_main_template_decl : Error<"'main' cannot be a template">;
def err_main_returns_nonint : Error<"'main' must return 'int'">;
+def warn_main_returns_nonint : ExtWarn<"return type of 'main' is not 'int'">,
+ InGroup<MainReturnType>;
def err_main_surplus_args : Error<"too many parameters (%0) for 'main': "
"must be 0, 2, or 3">;
def warn_main_one_arg : Warning<"only one parameter on 'main' declaration">,
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index feffaf1..48f6e1c 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -5794,8 +5794,14 @@ void Sema::CheckMain(FunctionDecl* FD, const DeclSpec& DS) {
const FunctionType* FT = T->getAs<FunctionType>();
if (!Context.hasSameUnqualifiedType(FT->getResultType(), Context.IntTy)) {
- Diag(FD->getTypeSpecStartLoc(), diag::err_main_returns_nonint);
- FD->setInvalidDecl(true);
+ if (getLangOptions().CPlusPlus) {
+ Diag(FD->getTypeSpecStartLoc(), diag::err_main_returns_nonint);
+ FD->setInvalidDecl(true);
+ } else {
+ // In C we allow main() to have non-integer return type, but we should
+ // warn about it.
+ Diag(FD->getTypeSpecStartLoc(), diag::warn_main_returns_nonint);
+ }
}
// Treat protoless main() as nullary.
@@ -7256,7 +7262,8 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
if (FD->isMain()) {
// C and C++ allow for main to automagically return 0.
// Implements C++ [basic.start.main]p5 and C99 5.1.2.2.3.
- FD->setHasImplicitReturnZero(true);
+ if (FD->getResultType()->isIntegerType())
+ FD->setHasImplicitReturnZero(true);
WP.disableCheckFallThrough();
} else if (FD->hasAttr<NakedAttr>()) {
// If the function is marked 'naked', don't complain about missing return
diff --git a/test/Sema/warn-main-returns-nonint.c b/test/Sema/warn-main-returns-nonint.c
new file mode 100644
index 0000000..e1dc114
--- /dev/null
+++ b/test/Sema/warn-main-returns-nonint.c
@@ -0,0 +1,3 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+void main() {} // expected-warning {{return type of 'main' is not 'int'}}
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