[cfe-commits] [LLVMdev] clang errors on void main()

[Vasiliy Korchagin]

On 12.02.2012 07:39, Chandler Carruth wrote:
> On Sat, Feb 11, 2012 at 5:31 AM, Vasiliy Korchagin 
> <korchagin at ispras.ru <mailto:korchagin at ispras.ru>> 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
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