Re: c++/8631: bug in typecasting the return value of a function

Re: c++/8631: bug in typecasting the return value of a function

[bangerth]

Synopsis: bug in typecasting the return value of a function

State-Changed-From-To: open->closed
State-Changed-By: bangerth
State-Changed-When: Tue Nov 19 07:01:18 2002
State-Changed-Why:
    User error. You are trying nonsense and getting nonsense. No
    surprise.
    
    Had you used a static_cast instead of the C-style cast like
    this:
       f2( static_cast<CAST (*)(int)>(&f1), 4 );
    then the compiler would tell you quite correctly:
    tmp/g> /home/bangerth/bin/gcc-3.3x-pre/bin/c++ x.cc
    x.cc: In function `int main()':
    x.cc:18: error: invalid static_cast from type `int (*)(int)' to type `
       std::complex<double> (*)(int)'

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8631

c++/8631: bug in typecasting the return value of a function

[gkmohan]

>Number:         8631
>Category:       c++
>Synopsis:       bug in typecasting the return value of a function
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Nov 18 18:26:00 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     gkmohan@ece.arizona.edu
>Release:        unknown-1.0
>Organization:
>Environment:

>Description:
typecasting a function pointer to return different value seg faults or returns nonsense (depending on the version)

this is what g++ -v returns
-----------------------------------------------------
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.96/specs
gcc version 2.96 20000731 (Red Hat Linux 7.1 2.96-85)
-----------------------------------------------------

--file test.cc--
#include <iostream.h>
#include <complex.h>

#define CAST complex<double>

int f1( int x )
{
   return x;
}

void f2( CAST (*f)(int), int x )
{
   cout << (*f)(x);
}

main()
{
   f2( (CAST (*)(int)) &f1, 4 );
}
>How-To-Repeat:
g++ -o test test.cc
./test
>Fix:
:-< none
>Release-Note:
>Audit-Trail:
>Unformatted: