MISRA C:2012 Dir 4.12

Dynamic memory allocation shall not be used

Description

Rule Definition

Dynamic memory allocation shall not be used¹ .

Rationale

Using dynamic memory allocation and deallocation routines provided by the Standard Library or third-party libraries can cause undefined behavior. For instance:

• You use free to deallocate memory that you did not allocate with malloc, calloc, or realloc.

• You use a pointer that points to a freed memory location.

• You access allocated memory that has no value stored into it.

Dynamic memory allocation and deallocation routines from third-party libraries are likely to exhibit similar undefined behavior.

If you choose to use dynamic memory allocation and deallocation routines, ensure that your program behavior is predictable. For example, ensure that you safely handle allocation failure due to insufficient memory.

Troubleshooting

If you expect a rule violation but do not see it, refer to Diagnose Why Coding Standard Violations Do Not Appear as Expected.

Examples

Use of malloc, calloc, realloc and free

#include <stdlib.h>

static int foo(void);

typedef struct struct_1 {
    int a;
    char c;
} S_1;

static int foo(void) {

    S_1 * ad_1;
    int  * ad_2;
    int  * ad_3;

    ad_1 = (S_1*)calloc(100U, sizeof(S_1));        /* Non-compliant */
    ad_2 = malloc(100U * sizeof(int));             /* Non-compliant */
    ad_3 = realloc(ad_3, 60U * sizeof(long));      /* Non-compliant */

    free(ad_1);                                    /* Non-compliant */
    free(ad_2);                                    /* Non-compliant */
    free(ad_3);                                    /* Non-compliant */

    return 1;
}

In this example, the rule is violated when the functions malloc, calloc, realloc and free are used.

Check Information

Group: Code Design

Category: Required

AGC Category: Required

Version History

Introduced in R2019b