[cfe-users] clang++-3.3 reject valid ?

[David Blaikie]

On Thu, Apr 11, 2013 at 8:51 AM, Дмитрий Дьяченко <dimhen at gmail.com> wrote:
> Hi!
>
> The following code
> $ cat -n x.ii
>      1    extern "C" typedef struct
>      2    {
>      3        volatile struct
>      4        {
>      5        } fields;
>      6    }
>      7    CSPHandleState;
>      8    typedef struct
>      9    {
>     10        CSPHandleState state;
>     11    }
>     12    CSPHandle;
>     13    CSPHandle a;
>     14    void
>     15    fn1 ()
>     16    {
>     17        CSPHandleState b;
>     18        b = a.state;
>     19    }
>
>
> rejected by clang++
> $ /home/dimhen/build/csa/Release+Asserts/bin/clang++ -fsyntax-only -x c++ x.ii
> x.ii:1:20: error: member function 'operator=' not viable: 'this'
> argument has type
>       'volatile struct <anonymous struct at x.ii:3:14>', but function
> is not marked
>       volatile
> extern "C" typedef struct
>                    ^~~~~~
> x.ii:3:14: note: 'operator=' declared here
>     volatile struct
>              ^
> x.ii:18:7: note: implicit default copy assignment operator for
> 'CSPHandleState' first
>       required here
>     b = a.state;
>       ^
> 1 error generated.
>
> $ /home/dimhen/build/csa/Release+Asserts/bin/clang++ -v
> clang version 3.3 (trunk 179273)
> Target: x86_64-unknown-linux-gnu
> Thread model: posix
>
>
> but gcc accept this
> $ g++ -Wall -Wextra -fsyntax-only x.ii
> [dimhen at dim clang]$ echo $?
> 0
>
> gcc versions:
> gcc version 4.7.2 20121109 (Red Hat 4.7.2-8) (GCC)
> gcc version 4.9.0 20130411 (experimental) [trunk revision 197693] (GCC)
>
> Original file (not the reduced testcase) was successfully compiled with
> many gcc versions (many versions from 3.2.3 to 4.9), xlc (AIX 5/6/7),
> suncc (Solaris 9/10 x64/sparc), MS Visual Studio (many versions from
> 2005 to 2012)
>
>
> So, my question is: what is right behavior?

Seems like a case of accepts-invalid in other compilers. If you do the
copy explicitly rather than via the implicit copy ctor, it fails:

struct foo { };
volatile foo f;
f = foo(); // passing ‘volatile foo’ as ‘this’ argument of ‘foo&
foo::operator=(const foo&)’ discards qualifiers [-fpermissive]

(additional errors occur if you try to copy from a volatile as well as
to a volatile)

In fact, while reducing your test case, I even managed to ICE GCC:

truct foo { };
  typedef struct
  {
      volatile foo fields;
  }
  CSPHandleState;
  CSPHandleState a;
  void
  fn1 ()
  {
      CSPHandleState b;
      b.fields = foo();
  }