[Bug c++/25992] New: condition expression and strings literal

[Bug c++/25992] New: condition expression and strings literal

[anton dot kirillov at rd-software dot com]

void foo( char* );

int main()
{
        foo( 0 ? "a" : "b" ); // 
}

The type of expression (0 ? "a" : "b") is const char[2] but it cannot be
transformed to char*, however it works.

Why?


-- 
           Summary: condition expression and strings literal
           Product: gcc
           Version: 3.4.5
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: anton dot kirillov at rd-software dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25992

[Bug c++/25992] conditional expression and strings literal

[pinskia at gcc dot gnu dot org]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 293 bytes --]



------- Comment #1 from pinskia at gcc dot gnu dot org  2006-01-27 12:39 -------
earth:~>g++ t.cc -pedantic -Wwrite-strings
t.cc: In function ‘int main()’:
t.cc:5: warning: deprecated conversion from string constant to ‘char*’'


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25992

[Bug c++/25992] conditional expression and strings literal

[anton dot kirillov at rd-software dot com]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 780 bytes --]



------- Comment #2 from anton dot kirillov at rd-software dot com  2006-01-27 13:12 -------
(In reply to comment #1)
> earth:~>g++ t.cc -pedantic -Wwrite-strings
> t.cc: In function ‘int main()’:
> t.cc:5: warning: deprecated conversion from string constant to ‘char*’'
> 

Conversion from string constant to ‘char*’' it's legacy from C, but GCC should
not perceive it as const char*, because the type of expression is const char[]!

I think GCC have defined it as a compile-time constant, but it's infeasible
solution. 

In other situation it behaves correctly:

void foo( char* );

int main()
{
        bool flag = false;
        foo( flag ? "a" : "b" ); // error ( cannot convert from const char* to
char* )
}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25992

[Bug c++/25992] conditional expression and strings literal

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2006-01-27 13:59 -------
I have not looked into the standard yet but if GCC's warning message is correct
this is valid but deprecated code which allows for a compiler to accept it or
not.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25992

[Bug c++/25992] conditional expression and strings literal

[anton dot kirillov at rd-software dot com]

------- Comment #4 from anton dot kirillov at rd-software dot com  2006-01-27 14:20 -------
(In reply to comment #3)
> I have not looked into the standard yet but if GCC's warning message is correct
> this is valid but deprecated code which allows for a compiler to accept it or
> not.
> 

deprecated this converiont:

void foo( char* )
{
}

int main()
{
        foo( "lalala" ); 
}

i.e. convresion from strings literal to char*, but the result of expression (0
? "a" : "b") IS NOT STRING LITERAL!!! IT'S CONST CHAR[2]!!! ( See 5.16 )


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25992

[Bug c++/25992] conditional expression and strings literal

[bangerth at dealii dot org]

------- Comment #5 from bangerth at dealii dot org  2006-03-08 05:02 -------
Confirmed. These two lines should behave the same, but don't:
--------------
extern bool flag;
int main()
{
  char* p;
  p = (true ? "a" : "lalala" );
  p = (flag ? "a" : "lalala" ); 
}
--------------

g/x> /home/bangerth/bin/gcc-4.2*/bin/c++ -c x.cc -Wwrite-strings
x.cc: In function ‘int main()’:
x.cc:5: warning: deprecated conversion from string constant to
‘char*’'
x.cc:6: error: invalid conversion from ‘const char*’ to
‘char*’

W.


-- 

bangerth at dealii dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |diagnostic
   Last reconfirmed|0000-00-00 00:00:00         |2006-03-08 05:02:36
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25992

[Bug c++/25992] conditional expression and strings literal

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25992

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

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

[Bug c++/25992] conditional expression and strings literal

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25992

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|anton.kirillov@rd-software. |
                   |com, gcc-bugs at gcc dot gnu.org   |
           Assignee|unassigned at gcc dot gnu.org      |paolo.carlini at oracle dot com

--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Mine.