[Bug c++/55280] New: Compiler error: Class definition is recognized as function declaration

[Bug c++/55280] New: Compiler error: Class definition is recognized as function declaration

[guangmuzhu at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55280

             Bug #: 55280
           Summary: Compiler error: Class definition is recognized as
                    function declaration
    Classification: Unclassified
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: guangmuzhu@gmail.com


A and B are both class. If a object is defined by "A a(B());", compiler reports
a is none-class type A(B (*)()).
I guess g++ translates it to "B temp(); A a(b);". If a is defined by "A
a(B(argument));", it's OK. But unfortunately, default constructor is not
allowed to be used like "B temp();", temp is declared as a function.
ps: vs 2008 doesn't have the problem

[Bug c++/55280] Compiler error: Class definition is recognized as function declaration

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55280

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-11-12 06:36:20 UTC ---
A a(B()); is a function declaration and not a variable declaration.  This is
one of the ambiguities of the parsing which the C++ standard decided it was a
function rather than a variable.

[Bug c++/55280] Compiler error: Class definition is recognized as function declaration

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55280

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-11-12 09:16:39 UTC ---
As Andrew said, this is not a bug, see
http://en.wikipedia.org/wiki/Most_vexing_parse

You can force it to be parsed as a variable declaration with A a((B()))

[Bug c++/55280] Compiler error: Class definition is recognized as function declaration

[guangmuzhu at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55280

--- Comment #3 from Guangmu Zhu <guangmuzhu at gmail dot com> 2012-11-12 09:22:01 UTC ---
(In reply to comment #2)
> As Andrew said, this is not a bug, see
> http://en.wikipedia.org/wiki/Most_vexing_parse
> 
> You can force it to be parsed as a variable declaration with A a((B()))

I got it. Thanks a lot!