Re: StackGuard with ... Re: [Paper] Format bugs.

[stanislav shalunov <shalunov () INTERNET2 EDU>]

"Stephen J. Friedl" <friedl () MTNDEW COM> writes:

> The first thing to do is turn on the damn compiler warnings, because more
> and more compilers actually do check printf-like parameters for you. GNU C
> does this, as do numerous commercial compilers:
>
>          $ cat test.c
>          #include <stdio.h>
>
>          int main(void)
>          {
>                  printf("i = %d\n");             <--- missing parameter!
>          }
>          $ gcc -Wall test.c      <-- try again with real warnings
>          test.c: In function `main':
>          test.c:5: warning: too few arguments for format

Turning on compiler warnings is nice, of course, and I always have at
least -Wall -W -pedantic on with GCC.

However, in this case compiler warnings buy you nothing.

The most trivial examples aren't dealt with properly:

$ cat try.c
#include <stdio.h>

int
main()
{
        char buf[1024];
        fgets(buf, sizeof buf, stdin);
        printf(buf);
        exit(0);
}
$ gcc -Wall -W -pedantic try.c
$ ./a.out
%p
0xa7025
$