testing the clang static code analyzer

Clang Frontend
1

Hi,

I installed the Clang Static Code Analyzer and tried testing it with a very simple example:

#include <stdio.h>

#include <stdlib.h>

Int main(int ac, char* argv)

{

int a;

char *string;

string = (char*) malloc(10);

string[11] = ‘X’;

return *(int *)0;

}

I expected 4 errors to be discover:

  1. Unused variable: a

  2. Out of bound access to array string

  3. Memory leak: string

  4. Dereference of null pointer at the return statement

But instead only one error was discovered (error number 4)

Can you please help me figure out why I don’t get all the errors?

Thanks,

Lior Brafman

R&D
CheckPoint

2

Hi,

I installed the Clang Static Code Analyzer and tried testing it with a very simple example:
#include <stdio.h>
#include <stdlib.h>

Int main(int ac, char* argv)
{
                int a;
                char *string;

                string = (char*) malloc(10);
                string[11] = ‘X’;
                return *(int *)0;
}

I expected 4 errors to be discover:
1. Unused variable: a

We are warning about this one if the value is being assigned to:
                int a;
                a = 2;

Though, we do not warn when it's not being assigned to to allow code like this:
int a;
if (flag) {
  a = 1;
  use (a);
}
// We don't want to warn here.

2. Out of bound access to array string

Currently, we do not have any on-by-default checker that would catch this.

3. Memory leak: string

We suppress leaks and other less critical issues if they occur on the same path as a very serious issue (such as a null ptr dereference). This is a heuristic which is supposed to show only the most important from a set of related issues. The heuristic is very simple, so it works agains us in this case. If you remove the null pointer dereference, you'll see the leak warning.

3

The analyzer also generally doesn't show errors that the compiler knows how to catch:

  warning: unused variable 'a' [-Wunused-variable]

-Wunused and -Wall include -Wunused-variable.

Jordan