PARM_NULL
Array parameter is NULL
Problem
Diagnosis (at runtime)
Repair

PARM_NULL

Array parameter is NULL

This error is generated whenever a parameter declared as an array is actually passed a NULL pointer.

Problem

The following code fragment shows a function which is declared as having an array parameter, but which is invoked with a NULL pointer. The value of array is NULL because it is a global variable, initialized to zero by default.

	1:	/*
	2:	 * File: parmnull.c
	3:	 */
	4:	int foo(a)
	5:		int a[];
	6:	{ 
	7:		return 12; 	
	8:	}
	9:
	10:	int *array;
	11:
	12:	main()
	13:	{	
	14:		foo(array);	
	15:		return (0);
	16:	}

Diagnosis (at runtime)

	[parmnull:6] **PARM_NULL**
1.	>> {
	
2.		Array parameter is null: a

		Stack trace where the error occurred:
3.			 foo() parmnull.c, 6
               		main() parmnull.c, 14

1. Source line at which the problem was detected.
2. Description of the problem and the name of the parameter that is in error.
3. Stack trace showing the function call sequence leading to the error.

Repair

A common cause of this error is the one given in this example, a global pointer which is initialized to zero by the compiler and then never reassigned. The correction for this case is to include code to initialize the pointer, possibly by allocating dynamic memory or by assigning it to some other array object.

For example, we could change the main routine of the example to

        main()
	{
             int local[10];

             array = local;
             foo(array);
	}

This problem can also occur when a pointer is set to NULL by the code (perhaps to indicate a freed block of memory) and then passed to a routine that expects an array as an argument.

In this case, Insure++ distinguishes between functions whose arguments are declared as arrays

	int foo(int a[])
	{

and those with pointer arguments

	int foo(int *a)
	{

The latter type will not generate an error if passed a NULL argument, while the former will.

A final common problem is caused when one of the dynamic memory allocation routines, malloc, calloc, or realloc, fails and returns a NULL pointer. This can happen either because your program passes bad arguments or simply because it asks for too much memory. A simple way of finding this problem with Insure++ is to enable the RETURN_FAILURE error code via your .psrc file and run the program again. It will then issue diagnostic messages every time a system call fails, including the memory allocation routines.

If your application cannot avoid passing a NULL pointer to a routine, you should either change the declaration of its argument to the second style or suppress these error messages by adding the option

	insure++.suppress PARM_NULL

to the .psrc file.

PARM_DANGLING

PARM_UNINIT_PTR