Attempting to dereference an invalid pointer results in undefined program behavior, typically abnormal program termination. Given this, invalid pointers should not be dereferenced.
Non-compliant Example
In this example, input_str is copied into dynamically allocated memory referenced by str. If malloc() }} fails, it returns an invalid (null) pointer that is assigned to {{str. When str is dereferenced in strcpy(), the program behave in an unpredictable manner.
... char *str = malloc(size_of_input_str); strcpy(str, input); ...
Compliant Solution
To correct this error, ensure the pointer returned by malloc() is not invalid (null). In addition to this rule, this should be done in accordance with rule MEM32-C. Detect and handle critical memory allocation errors.
...
char *str = malloc(size_of_input_str);
if (str == NULL) {
/* Handle Allocation Error */
}
strcpy(str, input_str);
...
Priority and Level
Dereferencing null pointers typically results in a denial of service condition.
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References
- ISO/IEC 9899-1999 6.3.2.3 Pointers