[PATCH] Fix PR15558

[Matt Beaumont-Gay]

Ping.

On Fri, Mar 29, 2013 at 3:19 PM, Matt Beaumont-Gay <matthewbg at google.com> wrote:
> Hi rsmith, nlewycky,
>
> When preparing to warn about an unused static member variable, which we've decided is unused because its type has internal linkage, don't warn if the variable is in a header. The definition and use may be in another TU.
>
> I had to reshuffle the test a little because we suppress unused-variable warnings after we've emitted an error.
>
> http://llvm-reviews.chandlerc.com/D597
>
> Files:
>   lib/Sema/Sema.cpp
>   test/SemaCXX/Inputs/warn-unused-variables.h
>   test/SemaCXX/warn-unused-variables-error.cpp
>   test/SemaCXX/warn-unused-variables.cpp
>
> Index: lib/Sema/Sema.cpp
> ===================================================================
> --- lib/Sema/Sema.cpp
> +++ lib/Sema/Sema.cpp
> @@ -751,9 +751,11 @@
>          if (DiagD->isReferenced()) {
>            Diag(DiagD->getLocation(), diag::warn_unneeded_internal_decl)
>                  << /*variable*/1 << DiagD->getDeclName();
> -        } else {
> +        } else if (getSourceManager().isFromMainFile(DiagD->getLocation())) {
> +          // If the decl is in a header, it may be used in some other TU, so
> +          // only warn if it's in the main file.
>            Diag(DiagD->getLocation(), diag::warn_unused_variable)
> -                << DiagD->getDeclName();
> +              << DiagD->getDeclName();
>          }
>        }
>      }
> Index: test/SemaCXX/Inputs/warn-unused-variables.h
> ===================================================================
> --- /dev/null
> +++ test/SemaCXX/Inputs/warn-unused-variables.h
> @@ -0,0 +1,11 @@
> +// Verify that we don't warn about variables of internal-linkage type in
> +// headers, as the use may be in another TU.
> +namespace PR15558 {
> +namespace {
> +class A {};
> +}
> +
> +class B {
> +  static A a;
> +};
> +}
> Index: test/SemaCXX/warn-unused-variables-error.cpp
> ===================================================================
> --- /dev/null
> +++ test/SemaCXX/warn-unused-variables-error.cpp
> @@ -0,0 +1,10 @@
> +// RUN: %clang_cc1 -fsyntax-only -Wunused-variable -verify %s
> +
> +namespace PR6948 {
> +  template<typename T> class X; // expected-note{{template is declared here}}
> +
> +  void f() {
> +    X<char> str (read_from_file()); // expected-error{{use of undeclared identifier 'read_from_file'}} \
> +                                       expected-error{{implicit instantiation of undefined template 'PR6948::X<char>'}}
> +  }
> +}
> Index: test/SemaCXX/warn-unused-variables.cpp
> ===================================================================
> --- test/SemaCXX/warn-unused-variables.cpp
> +++ test/SemaCXX/warn-unused-variables.cpp
> @@ -41,15 +41,6 @@
>    (void)i;
>  }
>
> -namespace PR6948 {
> -  template<typename T> class X; // expected-note{{template is declared here}}
> -
> -  void f() {
> -    X<char> str (read_from_file()); // expected-error{{use of undeclared identifier 'read_from_file'}} \
> -                                       expected-error{{implicit instantiation of undefined template 'PR6948::X<char>'}}
> -  }
> -}
> -
>  void unused_local_static() {
>    static int x = 0;
>    static int y = 0; // expected-warning{{unused variable 'y'}}
> @@ -135,3 +126,5 @@
>      S2 s((S1()));
>    }
>  }
> +
> +#include "Inputs/warn-unused-variables.h"