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

[Chandler Carruth]

On Sun, Feb 12, 2012 at 6:17 AM, Vasiliy Korchagin <korchagin at ispras.ru>wrote:

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

This is super close. Two minor nits, and it should be good-to-go:

1) The canonical prefix for an ExtWarn diagnostic is "ext_", not "warn_".

2) I would name the test something more generic so we can fold more main
tests into this file. 'main.c' would be fine.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20120212/c423047a/attachment.html>