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Code Block

bgColor	#ccccff

void clear(int array[], size_t sizelen) {
  size_t i;
  for (i = 0; i < sizelen; i++) {
     array[i] = 0;
  }
}

void dowork(void) {
  int dis[12];

  clear(dis, sizeof(dis) / sizeof(dis[0]));
  /* ... */
}

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In this noncompliant code example, the sizeof a does not equal 100 * sizeof(int). This is 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

bgColor	#FFcccc

enum {ARR_LEN = 100};

void clear(int a[100ARR_LEN]) {
  memset(a, 0, sizeof (a)); /* error */
}

int main(void) {
  int b[100ARR_LEN];
  clear(b);
  assert(b[50ARR_LEN / 2]==0); /* may fail */
  return 0;
}

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In this compliant solution, the size is specified using the expression 100 len * sizeof(int).

Code Block

bgColor	#ccccff

enum {ARR_LEN = 100};

void clear(int a[100], size_t len) {
  memset(a, 0, 100len * sizeof(int)); 
}

int main(void) {
  int b[100ARR_LEN];
  clear(b, ARR_LEN);
  assert(b[50ARR_LEN / 2]==0); /* cannot fail */
  return 0;
}

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