c/6980: -Wbad-function-cast gives bogus warning for (double) rand()

c/6980: -Wbad-function-cast gives bogus warning for (double) rand()

[richdawe]

>Number:         6980
>Category:       c
>Synopsis:       -Wbad-function-cast gives bogus warning for (double) rand()
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jun 10 01:56:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Richard Dawe
>Release:        gcc 3.1
>Organization:
>Environment:
DJGPP ports of gcc 3.1 & binutils 2.11.2, DJGPP CVS, running on Windows 98 SE
>Description:
Here is a simple test case:

---Start program---
#include <limits.h>
#include <stdlib.h>

int
main (void)
{
  double d;

  d = (double) rand() / RAND_MAX;

  return(EXIT_SUCCESS);
}
---End program---

I compile the program like this and get the following warnings:

bash-2.04$ gcc -Wall -Wbad-function-cast -c a.c
a.c: In function `main':
a.c:9: warning: cast does not match function type

rand is defined in <stdlib.h> like this:

int     rand(void);

Since an integer can fit into a double, I don't understand why this code gives a warning. We've discussed the warning on djgpp-workers@delorie.com and most people think it's a bug.

Thank you for your time. Regards, Richard Dawe
>How-To-Repeat:

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:

Re: c/6980: -Wbad-function-cast gives bogus warning for (double) rand()

[bangerth]

Synopsis: -Wbad-function-cast gives bogus warning for (double) rand()

State-Changed-From-To: open->analyzed
State-Changed-By: bangerth
State-Changed-When: Fri Mar  7 02:42:19 2003
State-Changed-Why:
    Correct. Testcase:
    -------------------
    int foo();
    void bar () {
      (double) foo();
    }
    -----------------------
    Output is bogus:
    g/x> /home/bangerth/bin/gcc-3.4-pre/bin/gcc -Wbad-function-cast -c x.c
    x.c: In function `bar':
    x.c:3: warning: cast does not match function type
    
    This is gccs behavior since seemingly forever.
    
    W.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6980