RFC: GCC should warn when evaluating a pointer return type from a function used in a conditional that performs arithmetic with it

["Darryl L. Miles" <darryl-mailinglists@xxxxxxxxxxxx>]

Subject: RFC: GCC should warn when evaluating a pointer return type from 
a function used in a conditional that performs arithmetic with it


Shouldn't GCC generate some form of warning with the following code, for 
the "if(foobar(i) < 0)" statement ?

It does generate a warning if you use "int j = foobar(i);"

I would think this sort of error should be a default warning (i.e. not 
need to specifying any additional -W option) and it should certainly be 
caught when specifying "-Wall".

Tried with:

gcc version 3.4.2 20041017 (Red Hat 3.4.2-6.fc3)
gcc version 4.0.2 20051125 (Red Hat 4.0.2-8)
gcc version 4.2.1



I don't think MSVC warns but SunPro C compiler (with Solaris 10 / Sun 
Studio 12) does.

Request for comments,

Darryl


#include <stdio.h>

extern char *foobar(int a);

char *
foobar(int a)
{
       static char buf[128+1];
       sprintf(buf, "%d", a);
       return buf;
}

int
main(int argc, char *argv[])
{
       char *cp;
       int i;

       i = 42;
       /* vvv SHOULDNT THIS GENERATE SOME FORM OF WARNING ??? */
       if(foobar(i) < 0) {
               printf("TRUE\n");
       } else {
               printf("FALSE\n");
       }

       return 0;
}