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-assign-pos.

Coding standards

Code examples

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

#include <string.h>

char *getenv(const char *name)
{
  return strcmp(name, "HOME")==0 ? "/" : NULL;
}

int ex(void)
{
  char *p = getenv("USER");
  return *p;  //p might be NULL
}

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

#include <stdlib.h>

int main(void)
{
  int *p = malloc(sizeof(int));
  if (p != 0) {
    *p = 4;
  }
  return (int)p;
}