r212171 - Don't accept qualified 'int' main return types in C++ or standard C mode

[Matt Calabrese]

I'm probably mis-remembering, but I could have sworn that for built-in
types, cv-qualification was always ignored in the return type such that
"int foo()" and "int const foo()" were the same, with cv-qualification only
mattering for class types.


On Wed, Jul 2, 2014 at 12:07 AM, Alp Toker <alp at nuanti.com> wrote:

> Author: alp
> Date: Wed Jul  2 02:07:20 2014
> New Revision: 212171
>
> URL: http://llvm.org/viewvc/llvm-project?rev=212171&view=rev
> Log:
> Don't accept qualified 'int' main return types in C++ or standard C mode
>
> C++ [basic.start.main]p1: "It shall have a return type of type int"
>
> ISO C is also clear about this, so only accept 'int' with qualifiers in
> GNUMode
> C.
>
> Modified:
>     cfe/trunk/lib/Sema/SemaDecl.cpp
>     cfe/trunk/test/CXX/basic/basic.start/basic.start.main/p2.cpp
>     cfe/trunk/test/Sema/c89.c
>
> Modified: cfe/trunk/lib/Sema/SemaDecl.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=212171&r1=212170&r2=212171&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaDecl.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaDecl.cpp Wed Jul  2 02:07:20 2014
> @@ -7878,32 +7878,37 @@ void Sema::CheckMain(FunctionDecl* FD, c
>    assert(T->isFunctionType() && "function decl is not of function type");
>    const FunctionType* FT = T->castAs<FunctionType>();
>
> -  // All the standards say that main() should should return 'int'.
> -  if (Context.hasSameUnqualifiedType(FT->getReturnType(), Context.IntTy))
> {
> +  if (getLangOpts().GNUMode && !getLangOpts().CPlusPlus) {
> +    // In C with GNU extensions we allow main() to have non-integer return
> +    // type, but we should warn about the extension, and we disable the
> +    // implicit-return-zero rule.
> +
> +    // GCC in C mode accepts qualified 'int'.
> +    if (Context.hasSameUnqualifiedType(FT->getReturnType(),
> Context.IntTy))
> +      FD->setHasImplicitReturnZero(true);
> +    else {
> +      Diag(FD->getTypeSpecStartLoc(), diag::ext_main_returns_nonint);
> +      SourceRange RTRange = FD->getReturnTypeSourceRange();
> +      if (RTRange.isValid())
> +        Diag(RTRange.getBegin(), diag::note_main_change_return_type)
> +            << FixItHint::CreateReplacement(RTRange, "int");
> +    }
> +  } else {
>      // In C and C++, main magically returns 0 if you fall off the end;
>      // set the flag which tells us that.
>      // This is C++ [basic.start.main]p5 and C99 5.1.2.2.3.
> -    FD->setHasImplicitReturnZero(true);
> -
> -  // In C with GNU extensions we allow main() to have non-integer return
> -  // type, but we should warn about the extension, and we disable the
> -  // implicit-return-zero rule.
> -  } else if (getLangOpts().GNUMode && !getLangOpts().CPlusPlus) {
> -    Diag(FD->getTypeSpecStartLoc(), diag::ext_main_returns_nonint);
> -
> -    SourceRange RTRange = FD->getReturnTypeSourceRange();
> -    if (RTRange.isValid())
> -      Diag(RTRange.getBegin(), diag::note_main_change_return_type)
> -          << FixItHint::CreateReplacement(RTRange, "int");
> -
> -  // Otherwise, this is just a flat-out error.
> -  } else {
> -    SourceRange RTRange = FD->getReturnTypeSourceRange();
> -    Diag(FD->getTypeSpecStartLoc(), diag::err_main_returns_nonint)
> -        << (RTRange.isValid() ? FixItHint::CreateReplacement(RTRange,
> "int")
> -                              : FixItHint());
>
> -    FD->setInvalidDecl(true);
> +    // All the standards say that main() should return 'int'.
> +    if (Context.hasSameType(FT->getReturnType(), Context.IntTy))
> +      FD->setHasImplicitReturnZero(true);
> +    else {
> +      // Otherwise, this is just a flat-out error.
> +      SourceRange RTRange = FD->getReturnTypeSourceRange();
> +      Diag(FD->getTypeSpecStartLoc(), diag::err_main_returns_nonint)
> +          << (RTRange.isValid() ? FixItHint::CreateReplacement(RTRange,
> "int")
> +                                : FixItHint());
> +      FD->setInvalidDecl(true);
> +    }
>    }
>
>    // Treat protoless main() as nullary.
>
> Modified: cfe/trunk/test/CXX/basic/basic.start/basic.start.main/p2.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/basic/basic.start/basic.start.main/p2.cpp?rev=212171&r1=212170&r2=212171&view=diff
>
> ==============================================================================
> --- cfe/trunk/test/CXX/basic/basic.start/basic.start.main/p2.cpp (original)
> +++ cfe/trunk/test/CXX/basic/basic.start/basic.start.main/p2.cpp Wed Jul
>  2 02:07:20 2014
> @@ -62,6 +62,8 @@ main( // expected-error {{first paramete
>  ) {
>  }
>
> +const int main(); // expected-error {{'main' must return 'int'}}
> +
>  #elif TEST7
>
>  // expected-no-diagnostics
>
> Modified: cfe/trunk/test/Sema/c89.c
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/c89.c?rev=212171&r1=212170&r2=212171&view=diff
>
> ==============================================================================
> --- cfe/trunk/test/Sema/c89.c (original)
> +++ cfe/trunk/test/Sema/c89.c Wed Jul  2 02:07:20 2014
> @@ -111,6 +111,8 @@ const array_of_pointer_to_CI mine3;
>
>  void main() {} /* expected-error {{'main' must return 'int'}} */
>
> +const int main() {} /* expected-error {{'main' must return 'int'}} */
> +
>  long long ll1 = /* expected-warning {{'long long' is an extension when
> C99 mode is not enabled}} */
>           -42LL; /* expected-warning {{'long long' is an extension when
> C99 mode is not enabled}} */
>  unsigned long long ull1 = /* expected-warning {{'long long' is an
> extension when C99 mode is not enabled}} */
>
>
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>



-- 
-Matt Calabrese
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