[Bug c++/46206] New: using typedef-name error with typedef name hiding struct name

[Bug c++/46206] New: using typedef-name error with typedef name hiding struct name

[nathan.keynes at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46206

           Summary: using typedef-name error with typedef name hiding
                    struct name
           Product: gcc
           Version: 4.1.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: nathan.keynes@oracle.com


G++ rejects the following code:

class Foo
{
    bool a, b, c, d;
    typedef struct Bar { } Bar;
    virtual void foo(void) {
        struct Bar bar;
    }
};

example.cc: In member function ‘virtual void Foo::foo()’:
example.cc:6: error: using typedef-name ‘Foo::Bar’ after ‘struct’
example.cc:4: error: ‘Foo::Bar’ has a previous declaration here
example.cc:6: error: invalid type in declaration before ‘;’ token

but accepts many similar examples, including:
class Foo
{
    bool a, b, c;
    typedef struct Bar { } Bar;
    virtual void foo(void) {
        struct Bar bar;
    }
};

This behaviour is reproducible on x86_64-redhat-linux (4.1.2 and 4.4.0) and
i386-pc-solaris2.11 (4.2.4, 4.3.4 and 4.5.1)

I'm uncertain if this is strictly legal or not per the standard, but it doesn't
seem to make sense to accept one of these cases but not the other.

[Bug c++/46206] using typedef-name error with typedef name hiding struct name

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46206

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2010.10.28 02:16:05
     Ever Confirmed|0                           |1

--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> 2010-10-28 02:16:05 UTC ---
Crazy.

[Bug c++/46206] using typedef-name error with typedef name hiding struct name

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46206

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> ---
The difference is that in the first case the TYPE_DECL Bar is regenerated and
the DECL_IMPLICIT_TYPEDEF_P bit is lost, the true value set earlier by
create_implicit_typedef is lost.

[Bug c++/46206] using typedef-name error with typedef name hiding struct name

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46206

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> ---
More correctly: it seems that when we parse "typedef struct Bar { } Bar;" we
create two TYPE_DECL: first, one marked as DECL_IMPLICIT_TYPEDEF_P in pushtag_1
(via create_implicit_typedef); then a second, real, one in grokdeclarator, via
build_lang_decl (TYPE_DECL... ). When we do lookup for "struct Bar bar", it can
happen, depending on layout details, that the *second* one is found, thus the
check in check_elaborated_type_specifier triggers.

[Bug c++/46206] using typedef-name error with typedef name hiding struct name

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46206

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |paolo.carlini at oracle dot com
   Target Milestone|---                         |4.9.0

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> ---
I have a patchlet which works for the testcase and passes testing. Let's fix
this insanity, one way or another.

[Bug c++/46206] using typedef-name error with typedef name hiding struct name

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46206

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Fixed.

[Bug c++/46206] using typedef-name error with typedef name hiding struct name

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46206

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |NEW
         Resolution|FIXED                       |---
           Assignee|paolo.carlini at oracle dot com    |unassigned at gcc dot gnu.org

--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Patch reverted. For some reason, it only worked on Linux.

[Bug c++/46206] using typedef-name error with typedef name hiding struct name

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46206

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.9.0                       |4.9.1

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.9.0 has been released

[Bug c++/46206] using typedef-name error with typedef name hiding struct name

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46206

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.9.1                       |4.9.2

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.9.1 has been released.

[Bug c++/46206] using typedef-name error with typedef name hiding struct name

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46206

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.9.2                       |4.9.3

--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.9.2 has been released.

[Bug c++/46206] using typedef-name error with typedef name hiding struct name

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46206

--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.9.3 has been released.

[Bug c++/46206] using typedef-name error with typedef name hiding struct name

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46206

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.9.3                       |4.9.4

[Bug c++/46206] using typedef-name error with typedef name hiding struct name

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46206

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=19538
           Keywords|                            |rejects-valid

--- Comment #11 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Nathan Keynes from comment #0)
> but accepts many similar examples, including:
> class Foo
> {
>     bool a, b, c;
>     typedef struct Bar { } Bar;
>     virtual void foo(void) {
>         struct Bar bar;
>     }
> };

That is no longer accepted, since r252005. So the difference was possibly a
bug, which got fixed, and now we consistently reject both, but ...

> I'm uncertain if this is strictly legal or not per the standard, but it
> doesn't seem to make sense to accept one of these cases but not the other.

It was made legal by https://wg21.link/cwg407 (c.f. PR 19538). Both examples
should compile.