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This noncompliant code attempts to allocated a flexible array member with a one element array as the final member. When the structure is instantiated, the size computed for malloc() is modified to account for the actual size of the dynamic array.
| Code Block | ||||
|---|---|---|---|---|
| ||||
struct flexArrayStruct {
int num;
int data[1];
};
/* ... */
size_t array_size;
size_t i;
/* initialize array_size */
/* space is allocated for the struct */
struct flexArrayStruct *structP
= (struct flexArrayStruct *)
malloc(sizeof(struct flexArrayStruct)
+ sizeof(int) * (array_size - 1));
if (structP == NULL) {
/* Handle malloc failure */
}
structP->num = 0;
/* access data[] as if it had been allocated
* as data[array_size] */
for (i = 0; i < array_size; i++) {
structP->data[i] = 1;
}
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This compliant solution uses the flexible array member to achieve a dynamically sized structure.
| Code Block | ||||
|---|---|---|---|---|
| ||||
struct flexArrayStruct{
int num;
int data[];
};
/* ... */
size_t array_size;
size_t i;
/* Initialize array_size */
/* Space is allocated for the struct */
struct flexArrayStruct *structP = (struct flexArrayStruct *)
malloc(sizeof(struct flexArrayStruct) + sizeof(int) * array_size);
if (structP == NULL) {
/* Handle malloc failure */
}
structP->num = 0;
/* Access data[] as if it had been allocated
* as data[array_size]
*/
for (i = 0; i < array_size; i++) {
structP->data[i] = 1;
}
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