...
| Code Block | ||||
|---|---|---|---|---|
| ||||
void clear(int array[]) {
for (size_t i = 0; i < sizeof(array) / sizeof(array[0]); ++i) {
array[i] = 0;
}
}
void dowork(void) {
int dis[12];
clear(dis);
/* ... */
}
|
Footnote 103 in Section section 6.5.3.4 of the C Standard [ISO/IEC 9899:2011] explains:
...
In this compliant solution, the size of the array is determined inside the block in which it is declared and passed as an argument to the function.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
void clear(int array[], size_t len) {
for (size_t i = 0; i < len; i++) {
array[i] = 0;
}
}
void dowork(void) {
int dis[12];
clear(dis, sizeof(dis) / sizeof(dis[0]));
/* ... */
}
|
...
In this noncompliant code example, the sizeof a does not equal 100 * sizeof(int) because the sizeof operator, when applied to a parameter declared to have array or function type, yields the size of the adjusted (pointer) type, even if the parameter declaration specifies a length.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
enum {ARR_LEN = 100};
void clear(int a[ARR_LEN]) {
memset(a, 0, sizeof(a)); /* error */
}
int main(void) {
int b[ARR_LEN];
clear(b);
assert(b[ARR_LEN / 2]==0); /* may fail */
return 0;
}
|
...
In this compliant solution, the size is specified using the expression len * sizeof(int).:
| Code Block | ||||
|---|---|---|---|---|
| ||||
enum {ARR_LEN = 100};
void clear(int a[], size_t len) {
memset(a, 0, len * sizeof(int));
}
int main(void) {
int b[ARR_LEN];
clear(b, ARR_LEN);
assert(b[ARR_LEN / 2]==0); /* cannot fail */
return 0;
}
|
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Tool | Version | Checker | Description | ||||||
|---|---|---|---|---|---|---|---|---|---|
Compass/ROSE |
|
| Can detect violations of the recommendation but cannot distinguish between incomplete array declarations and pointer declarations. | ||||||
| 401 S | Partially implemented. | |||||||
Splint |
|
|
|
...