QA·C Help - 2823

	2823	Suspicious: Arithmetic operation on NULL pointer.

NULL pointers

Dataflow analysis has identified a code construct which is suspicious. The code may be entirely safe but further investigation is advisable.

An arithmetic operation is being performed on a pointer value. Examination of the immediate context suggests that the pointer value could sometimes be NULL.

A null pointer may be assigned or compared, but any attempt to perform arithmetic operations on it will result in undefined behavior.

For example, in the code shown below, the pointer 'p' which is being incremented, will be NULL unless the parameter 'n' is greater than 0.


/*PRQA S 489,505,2017,2983,2986,3132,3199,3203,3227,3408,3412,3447,3673,4600 ++*/
#define NULL (void *)0

extern int ar[100];

extern void foo(int n)
{
    int  i;
    int *p = NULL;

    for (i = 0; i < n; ++i)
    {
        p = &ar[i];
    }

    p++;                /* 2823 */
}

See also:

2810 Constant: Dereference of NULL pointer.
2811 Definite: Dereference of NULL pointer.
2812 Apparent: Dereference of NULL pointer.
2813 Suspicious: Dereference of NULL pointer.
2814 Possible: Dereference of NULL pointer.
2820 Constant: Arithmetic operation on NULL pointer.
2821 Definite: Arithmetic operation on NULL pointer.
2822 Apparent: Arithmetic operation on NULL pointer.
2824 Possible: Arithmetic operation on NULL pointer.

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