[Bug c++/18113] New: compiler allows 2 copy constructors

[Bug c++/18113] New: compiler allows 2 copy constructors

[profvonsully at yahoo dot com]

The bug is simple : 
 lets say : 
  
" 
 class TObject; 
 typedef TObject& rObject; 
 class TObject 
     { 
     public: 
         TObject(){} 
         TObject(const TObject&); 
         TObject(const rObject); 
     }; 
  
 TObject::TObject(const TObject&) 
             { 
             char*s; 
             s="constructor 1"; 
             }  
          
 TObject::TObject(const rObject) 
             { 
             char*s; 
             s="constructor 2"; 
             } 
" 
In da function: 
" 
TObject F() 
     { 
     TObject AnObject; 
     TObject anotherObject=AnObject;//constructor 2 !!! 
     return AnObject; 
     }  
  
" constructor 2 will be called!

-- 
           Summary: compiler allows 2 copy constructors
           Product: gcc
           Version: 3.3.2
            Status: UNCONFIRMED
          Severity: critical
          Priority: P1
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: profvonsully at yahoo dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386
  GCC host triplet: i386
GCC target triplet: i386


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18113

[Bug c++/18113] compiler allows 2 copy constructors

[profvonsully at yahoo dot com]

------- Additional Comments From profvonsully at yahoo dot com  2004-10-22 16:53 -------
Created an attachment (id=7402)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=7402&action=view)
html file describing the bug

no comment ;)

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18113

[Bug c++/18113] compiler allows 2 copy constructors

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-10-22 17:13 -------
Not a bug.  The "const" in "const rObject" is meaning less in this context (the rObject is already const, 
references are const, what they refer to are not).

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|critical                    |normal
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18113

[Bug c++/18113] compiler allows 2 copy constructors

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-10-22 18:53 -------
Your second copy constructor will be called every time the argument 
given can't be bound to a reference. The code is perfectly legal, and 
the compiler needs to accept it. 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18113

[Bug c++/18113] compiler allows 2 copy constructors

[profvonsully at yahoo dot com]

------- Additional Comments From profvonsully at yahoo dot com  2004-10-26 18:41 -------
there is another example for those that did not look at the attachment(sorry 
for my initial language): 
 
class TObject; 
 typedef TObject& rObject; 
 class TObject 
     { 
     public: 
         TObject(){} 
         TObject(const rObject){}//the compiler does NOT realize that this is 
a copy constructor 
 //        TObject(const TObject&){} the compiler wants this to be a copy 
constructor  
 //       "error: no matching function for call to 
`TObject::TObject(TObject)'" :))))))) 
 //I am profvonsully@yahoo.com 
     }; 
      
 TObject GetAnObject() 
     { 
     TObject AnObject; 
     return AnObject; 
     } 
      
 void HandleObject(TObject toj) 
     { 
     } 
  
 void errors_are_here() 
     { 
     HandleObject 
         ( 
             GetAnObject() 
         );/*here g++ says an error exists*/ 
     } 

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18113

[Bug c++/18113] compiler allows 2 copy constructors

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-10-26 18:44 -------
Read my comment again, this is not a bug.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18113

[Bug c++/18113] compiler allows 2 copy constructors

[profvonsully at yahoo dot com]

------- Additional Comments From profvonsully at yahoo dot com  2004-10-26 18:45 -------
(In reply to comment #2) 
> look at the attahement ! 
 
 

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18113

[Bug c++/18113] compiler allows 2 copy constructors

[pinskia at gcc dot gnu dot org]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 238 bytes --]


------- Additional Comments From pinskia at gcc dot gnu dot org  2004-10-26 18:48 -------
  TObject(const rObject){} is the same as   TObject(TObject&){}

The const is ignored.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18113

[Bug c++/18113] compiler allows 2 copy constructors

[profvonsully at yahoo dot com]

------- Additional Comments From profvonsully at yahoo dot com  2004-10-26 19:05 -------
(In reply to comment #7 
i dont care about the const . i descovered the bug in the first example of the 
attcahment where the compiler prints an error that is not logic(in borland C++ 
i used TObject(rObject) with no problem). 
If a fuction returns a TObject and I pass the result to a function that 
receives a TObject an error ocurs !! pls make me understand this :) 

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18113

[Bug c++/18113] compiler allows 2 copy constructors

[profvonsully at yahoo dot com]

------- Additional Comments From profvonsully at yahoo dot com  2004-10-26 19:21 -------
!!!  
in the second example only one constructor is writeed (to be compiled) 
"TObject(rTObject)"!!(the other one is in a coment and ... errror) 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18113

[Bug c++/18113] compiler allows 2 copy constructors

[reichelt at gcc dot gnu dot org]

------- Additional Comments From reichelt at gcc dot gnu dot org  2004-10-26 20:34 -------
Here's a detailed explanation of the second example:

You are calling the function "void HandleObject(TObject toj);" as follows:
"HandleObject( GetAnObject() );"
To do this you need a copy constructor to copy the result of
"GetAnObject()" into "toj".

The only copy constructor that is available is "TObject(const rObject)"
which is essentially "TObject(TObject&)" and not "TObject(const TObject&)"
as one might think (see comment #2).

However, "TObject(TObject&)" can only take an lvalue (something that can
be modified) as argument, but "GetAnObject()" only provides an lvalue
(which cannot be modified). Therefore, gcc correctly complains that it
cannot find a suitable copy constructor.

This is a bug in your code and not in gcc.

Note, that the compiler is allowed to optimize away the copy constructor.
Nevertheless, it has to check whether the copy constructor is present.
Alas, many compilers forgot to check this.


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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18113