[cfe-commits] r173643 - Add a -pedantic warning: an anonymous union within an anonymous union is not

Alexey Samsonov samsonov at google.com
Mon Jan 28 00:20:46 PST 2013


On Mon, Jan 28, 2013 at 7:40 AM, Richard Smith <richard at metafoo.co.uk>wrote:

> On Sun, Jan 27, 2013 at 7:23 PM, NAKAMURA Takumi <geek4civic at gmail.com>wrote:
>
>> Richard, it brought many warnings on the tree.
>> http://bb.pgr.jp/builders/clang-3stage-x86_64-linux/builds/846
>>
>> What could we do? Fix extensions, or ... ?
>>
>
> Maybe we should just turn the warning off for LLVM and Clang;
>

FTR this change breaks self-hosted LLVM/Clang build with -Werror, which is
a bit frustrating. Can we temporary disable this warning by default or fix
its reports across LLVM/Clang code?


> this is a widely-available language extension which apparently no-one even
> noticed that we were using by accident. That said, the very first case
> where it fires looks like a pretty egregious violation of the rules.
>
>
>> ...Takumi
>>
>> 2013/1/28 Richard Smith <richard-llvm at metafoo.co.uk>:
>> > Author: rsmith
>> > Date: Sun Jan 27 18:54:05 2013
>> > New Revision: 173643
>> >
>> > URL: http://llvm.org/viewvc/llvm-project?rev=173643&view=rev
>> > Log:
>> > Add a -pedantic warning: an anonymous union within an anonymous union
>> is not
>> > permitted in standard C++, despite being silently accepted by many
>> (all?) major
>> > C++ implementations.
>> >
>> > Modified:
>> >     cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>> >     cfe/trunk/lib/Sema/SemaDecl.cpp
>> >     cfe/trunk/test/SemaCXX/anonymous-union.cpp
>> >     cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp
>> >
>> > Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>> > URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=173643&r1=173642&r2=173643&view=diff
>> >
>> ==============================================================================
>> > --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
>> > +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Sun Jan 27
>> 18:54:05 2013
>> > @@ -5344,6 +5344,9 @@ def err_anonymous_record_with_type : Err
>> >  def ext_anonymous_record_with_type : Extension<
>> >    "types declared in an anonymous %select{struct|union}0 are a
>> Microsoft "
>> >    "extension">, InGroup<Microsoft>;
>> > +def ext_anonymous_record_with_anonymous_type : Extension<
>> > +  "nested anonymous types are an extension">,
>> > +  InGroup<DiagGroup<"nested-anon-types">>;
>> >  def err_anonymous_record_with_function : Error<
>> >    "functions cannot be declared in an anonymous
>> %select{struct|union}0">;
>> >  def err_anonymous_record_with_static : Error<
>> >
>> > Modified: cfe/trunk/lib/Sema/SemaDecl.cpp
>> > URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=173643&r1=173642&r2=173643&view=diff
>> >
>> ==============================================================================
>> > --- cfe/trunk/lib/Sema/SemaDecl.cpp (original)
>> > +++ cfe/trunk/lib/Sema/SemaDecl.cpp Sun Jan 27 18:54:05 2013
>> > @@ -3198,6 +3198,12 @@ Decl *Sema::BuildAnonymousStructOrUnion(
>> >                << (int)Record->isUnion();
>> >              Invalid = true;
>> >            }
>> > +        } else {
>> > +          // This is an anonymous type definition within another
>> anonymous type.
>> > +          // This is a popular extension, provided by Plan9, MSVC and
>> GCC, but
>> > +          // not part of standard C++.
>> > +          Diag(MemRecord->getLocation(),
>> > +               diag::ext_anonymous_record_with_anonymous_type);
>> >          }
>> >        } else if (isa<AccessSpecDecl>(*Mem)) {
>> >          // Any access specifier is fine.
>> >
>> > Modified: cfe/trunk/test/SemaCXX/anonymous-union.cpp
>> > URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/anonymous-union.cpp?rev=173643&r1=173642&r2=173643&view=diff
>> >
>> ==============================================================================
>> > --- cfe/trunk/test/SemaCXX/anonymous-union.cpp (original)
>> > +++ cfe/trunk/test/SemaCXX/anonymous-union.cpp Sun Jan 27 18:54:05 2013
>> > @@ -9,7 +9,7 @@ struct X {
>> >      int i;
>> >      float f;
>> >
>> > -    union {
>> > +    union { // expected-warning{{nested anonymous types are an
>> extension}}
>> >        float f2;
>> >        mutable double d;
>> >      };
>> > @@ -101,7 +101,7 @@ void g() {
>> >  struct BadMembers {
>> >    union {
>> >      struct X { }; // expected-error {{types cannot be declared in an
>> anonymous union}}
>> > -    struct { int x; int y; } y;
>> > +    struct { int x; int y; } y; // expected-warning{{nested anonymous
>> types are an extension}}
>> >
>> >      void f(); // expected-error{{functions cannot be declared in an
>> anonymous union}}
>> >    private: int x1; // expected-error{{anonymous union cannot contain a
>> private data member}}
>> > @@ -128,7 +128,7 @@ namespace test4 {
>> >      struct { // expected-warning{{anonymous structs are a GNU
>> extension}}
>> >        int s0; // expected-note {{declared private here}}
>> >        double s1; // expected-note {{declared private here}}
>> > -      union {
>> > +      union { // expected-warning{{nested anonymous type}}
>> >          int su0; // expected-note {{declared private here}}
>> >          double su1; // expected-note {{declared private here}}
>> >        };
>> > @@ -136,7 +136,7 @@ namespace test4 {
>> >      union {
>> >        int u0; // expected-note {{declared private here}}
>> >        double u1; // expected-note {{declared private here}}
>> > -      struct { // expected-warning{{anonymous structs are a GNU
>> extension}}
>> > +      struct { // expected-warning{{anonymous structs are a GNU
>> extension}} expected-warning{{nested anonymous type}}
>> >          int us0; // expected-note {{declared private here}}
>> >          double us1; // expected-note {{declared private here}}
>> >        };
>> > @@ -187,7 +187,7 @@ namespace PR8326 {
>> >
>> >    private:
>> >      const union { // expected-warning{{anonymous union cannot be
>> 'const'}}
>> > -      struct { // expected-warning{{anonymous structs are a GNU
>> extension}}
>> > +      struct { // expected-warning{{anonymous structs are a GNU
>> extension}} expected-warning{{nested anonymous type}}
>> >          T x;
>> >          T y;
>> >        };
>> >
>> > Modified: cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp
>> > URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp?rev=173643&r1=173642&r2=173643&view=diff
>> >
>> ==============================================================================
>> > --- cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp (original)
>> > +++ cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp Sun Jan 27
>> 18:54:05 2013
>> > @@ -1153,8 +1153,8 @@ namespace ConvertedConstantExpr {
>> >  namespace IndirectField {
>> >    struct S {
>> >      struct { // expected-warning {{GNU extension}}
>> > -      union {
>> > -        struct { // expected-warning {{GNU extension}}
>> > +      union { // expected-warning {{nested anonymous types are an
>> extension}}
>> > +        struct { // expected-warning {{GNU extension}}
>> expected-warning {{nested anonymous types are an extension}}
>> >            int a;
>> >            int b;
>> >          };
>> >
>> >
>> > _______________________________________________
>> > cfe-commits mailing list
>> > cfe-commits at cs.uiuc.edu
>> > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>>
>
>
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-- 
Alexey Samsonov, MSK
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