Synopsis

A pointer is assigned a value that might be NULL, and then dereferenced.

Enabled by default

No

Severity/Certainty

High/Low

Full description

A pointer is assigned a value that might be NULL, and then dereferenced. Often the source of the potential NULL pointer is a memory allocation function like malloc(), or a sentinel value provided in a user function. This check is identical to CERT-EXP34-C_c.

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;
}