[Bug c++/48980] New: Misleading error message when a conversion is invalid while calling a protected base constructor

[Bug c++/48980] New: Misleading error message when a conversion is invalid while calling a protected base constructor

[dibeas at ieee dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48980

           Summary: Misleading error message when a conversion is invalid
                    while calling a protected base constructor
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: trivial
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: dibeas@ieee.org


Provided with this code:

class base {
protected:
   base( int * ) {}
};
struct derived : base {
   derived( const int * p ) : base( p ) {}
};

The compiler correctly detects that there is an error as using p as argument to
the constructor of base will break const-correctness. The error report
identifies that condition, but it also adds a misleading first error:

error.cpp: In constructor ‘derived::derived(const int*)’:
error.cpp:5: error: ‘base::base(int*)’ is protected
error.cpp:10: error: within this context
error.cpp:10: error: invalid conversion from ‘const int*’ to ‘int*’
error.cpp:10: error:   initializing argument 1 of ‘base::base(int*)’

Clearly base::base(int*) is protected, but it is accessible from the context of
the constructor derived::derived(const int*), and the first 3 lines should not
be part of the error message.

This can be reproduced with the default g++ in ubuntu/linaro, and also with g++
4.0.3 (I don't know the exact compiler flags used, but I believe the error to
be independent of compiler flags, if it is not, I can find out the exact flags
used).

g++ (Ubuntu/Linaro 4.4.4-14ubuntu5) 4.4.5

[Bug c++/48980] Misleading error message when a conversion is invalid while calling a protected base constructor

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48980

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-05-12 15:58:06 UTC ---
With 4.6 you just get:

d.cc: In constructor 'derived::derived(const int*)':
d.cc:6:39: error: invalid conversion from 'const int*' to 'int*' [-fpermissive]
d.cc:3:4: error:   initializing argument 1 of 'base::base(int*)' [-fpermissive]

[Bug c++/48980] Misleading error message when a conversion is invalid while calling a protected base constructor

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48980

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.6.0

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-07-24 20:18:33 UTC ---
Fixed in 4.6.0 and above.