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In this example, the function pointer fp is used to refer to the function strchr(). However, fp is declared without a function prototype. As a result, there is no type checking performed on the call to fp(12,2);.

#include <stdio.h>
#include <string.h>

char *(*fp) ();

int main(void) {
  char *c;
  fp = strchr;
  c = fp(12, 2);
  printf("%s\n", c);
  return 0;
}

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Declaring fp with a function prototype corrects this example.

#include <string.h>

char *(*fp) (const char *, int);

int main(void) {
  char *c;
  fp = strchr;
  c = fp("Hello",'H');
  printf("%s\n", c);
  return 0;
}

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In this noncompliant code example from a vulnerability in the useradd() function of the shadow-utils package CVE-2006-1174 , the third argument to open() has been accidentally omitted.

fd = open(ms, O_CREAT|O_EXCL|O_WRONLY|O_TRUNC);

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To correct this example, a third argument is specified in the call to open().

/* ... */
fd = open(ms, O_CREAT|O_EXCL|O_WRONLY|O_TRUNC, file_access_permissions);
if (fd == -1){
  /* Handle error */
}
/* ... */

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