Synopsis

Do not dereference null pointers.

Enabled by default

Yes

Severity/Certainty

High/High

Full description

Dereferencing a null pointer is undefined behavior. On many platforms, dereferencing a null pointer results in abnormal program termination, but this is not required by the standard. This check is identical to PTR-null-cmp-bef.

Coding standards

Code examples

The following code example fails the check and will give a warning:

#include <stdlib.h>

int example(void) {
  int *p;
  if (p == NULL) {
    *p = 4;  //dereference after comparison with NULL
  }
  return 1;
}

The following code example passes the check and will not give a warning about this issue:

#include <stdlib.h>

int example(void) {
  int *p;
  if (p != NULL) {
    *p = 4;  //OK - after comparison with non-NULL
  }
  return 1;
}