[cfe-commits] r150128 - in /cfe/trunk: include/clang/Basic/DiagnosticSemaKinds.td lib/Sema/SemaDecl.cpp test/SemaCXX/function-extern-c.cpp

[Matt Beaumont-Gay]

Hi Aaron,

The documentation for the corresponding MSVC warning states:

"This is legal if:
* All calls to this function occur from C++.
* The definition of the function is in C++."

For code which triggers the new warning, but is legal per those
criteria, how does one silence the warning?

Thanks,
Matt

On Wed, Feb 8, 2012 at 17:21, Aaron Ballman <aaron at aaronballman.com> wrote:
> Author: aaronballman
> Date: Wed Feb  8 19:21:34 2012
> New Revision: 150128
>
> URL: http://llvm.org/viewvc/llvm-project?rev=150128&view=rev
> Log:
> Adding support for warning when a non-C compatible user-defined type is returned from an extern "C" function.
>
> Fixes bug 6143
>
> Added:
>    cfe/trunk/test/SemaCXX/function-extern-c.cpp   (with props)
> Modified:
>    cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>    cfe/trunk/lib/Sema/SemaDecl.cpp
>
> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=150128&r1=150127&r2=150128&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Wed Feb  8 19:21:34 2012
> @@ -163,7 +163,9 @@
>  def warn_return_value_size: Warning<
>   "return value of %0 is a large (%1 bytes) pass-by-value object; "
>   "pass it by reference instead ?">, InGroup<LargeByValueCopy>;
> -
> +def warn_return_value_udt: Warning<
> +  "%0 has C-linkage specified, but returns user-defined type %1 which is "
> +  "incompatible with C">, InGroup<ReturnType>;
>  def warn_implicit_function_decl : Warning<
>   "implicit declaration of function %0">,
>   InGroup<ImplicitFunctionDeclare>, DefaultIgnore;
>
> Modified: cfe/trunk/lib/Sema/SemaDecl.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=150128&r1=150127&r2=150128&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaDecl.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaDecl.cpp Wed Feb  8 19:21:34 2012
> @@ -5774,6 +5774,17 @@
>         Context.BuiltinInfo.ForgetBuiltin(BuiltinID, Context.Idents);
>       }
>     }
> +
> +    // If this function is declared as being extern "C", then check to see if
> +    // the function returns a UDT (class, struct, or union type) that is not C
> +    // compatible, and if it does, warn the user.
> +    if (NewFD->isExternC()) {
> +      QualType R = NewFD->getResultType();
> +      if (!R.isPODType(Context) &&
> +          !R->isVoidType())
> +        Diag( NewFD->getLocation(), diag::warn_return_value_udt )
> +          << NewFD << R;
> +    }
>   }
>   return Redeclaration;
>  }
>
> Added: cfe/trunk/test/SemaCXX/function-extern-c.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/function-extern-c.cpp?rev=150128&view=auto
> ==============================================================================
> --- cfe/trunk/test/SemaCXX/function-extern-c.cpp (added)
> +++ cfe/trunk/test/SemaCXX/function-extern-c.cpp Wed Feb  8 19:21:34 2012
> @@ -0,0 +1,38 @@
> +// RUN: %clang_cc1 -Wreturn-type -fsyntax-only -std=c++11 -verify %s
> +
> +class A {
> +public:
> +  A(const A&);
> +};
> +
> +struct S {
> +  int i;
> +  double d;
> +
> +  virtual void B() {}
> +};
> +
> +union U {
> +  struct {
> +    int i;
> +    virtual void B() {} // Can only do this in C++11
> +  } t;
> +};
> +
> +struct S2 {
> +  int i;
> +  double d;
> +};
> +
> +extern "C" U f3( void ); // expected-warning {{'f3' has C-linkage specified, but returns user-defined type 'U' which is incompatible with C}}
> +extern "C" S f0(void); // expected-warning {{'f0' has C-linkage specified, but returns user-defined type 'S' which is incompatible with C}}
> +extern "C" A f4( void ); // expected-warning {{'f4' has C-linkage specified, but returns user-defined type 'A' which is incompatible with C}}
> +
> +// These should all be fine
> +extern "C" S2 f5( void );
> +extern "C" void f2( A x );
> +extern "C" void f6( S s );
> +extern "C" void f7( U u );
> +extern "C" double f8(void);
> +extern "C" long long f11( void );
> +extern "C" A *f10( void );
>
> Propchange: cfe/trunk/test/SemaCXX/function-extern-c.cpp
> ------------------------------------------------------------------------------
>    svn:eol-style = native
>
>
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