Page History

...

Noncompliant Code Example (Non-Prototype-Format Declarators)

Noncompliant This noncompliant code example uses the identifier-list form for parameter declarations:

int max(a, b)
int a, b;
{
  return a > b ? a : b;
}

Section Subclause 6.11.7 of the C Standard [ISO/IEC 9899:2011] states that "the use of function definitions with separate parameter identifier and declaration lists (not prototype-format parameter type and identifier declarators) is an obsolescent feature."

...

In this noncompliant code example, the function pointer fn_ptr refers to the function add(), which accepts three integer arguments. However, fn_ptr is specified to accept two integer arguments. Setting fn_ptr to refer to add() results in unexpected program behavior. This example also violates DCL35violates EXP37-C. Call functions with the correct number and type of arguments.:

int add(int x, int y, int z) {
   return x + y + z;
}

int main(int argc, char *argv[]) {
   int (*fn_ptr) (int, int);
   int res;
   fn_ptr = add;
   res = fn_ptr(2, 3);  /* incorrectIncorrect */
   /* ... */
   return 0;
}

Compliant Solution (Function Pointers)

...

int add(int x, int y, int z) {
   return x + y + z;
}

int main(int argc, char *argv[]) {
   int (*fn_ptr) (int, int, int) ;
   int res;
   fn_ptr = add;
   res = fn_ptr(2, 3, 4);
   /* ... */
   return 0;
}

Risk Assessment

Failing to include type information for function declarators can result in unexpected or unintended program behavior.

Automated Detection

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Related Guidelines

Bibliography

...

...

Image Modified Image Modified Image Modified