bugprone-suspicious-memset-usage¶
This check finds memset() calls with potential mistakes in their arguments. Considering the function as void* memset(void* destination, int fill_value, size_t byte_count), the following cases are covered:
Case 1: Fill value is a character ``‘0’``
Filling up a memory area with ASCII code 48 characters is not customary, possibly integer zeroes were intended instead. The check offers a replacement of '0' with 0. Memsetting character pointers with '0' is allowed.
Case 2: Fill value is truncated
Memset converts fill_value to unsigned char before using it. If fill_value is out of unsigned character range, it gets truncated and memory will not contain the desired pattern.
Case 3: Byte count is zero
Calling memset with a literal zero in its byte_count argument is likely to be unintended and swapped with fill_value. The check offers to swap these two arguments.
Corresponding cpplint.py check name: runtime/memset.
Examples:
void foo() {
int i[5] = {1, 2, 3, 4, 5};
int *ip = i;
char c = '1';
char *cp = &c;
int v = 0;
// Case 1
memset(ip, '0', 1); // suspicious
memset(cp, '0', 1); // OK
// Case 2
memset(ip, 0xabcd, 1); // fill value gets truncated
memset(ip, 0x00, 1); // OK
// Case 3
memset(ip, sizeof(int), v); // zero length, potentially swapped
memset(ip, 0, 1); // OK
}