blob: 82609d13e4efe7d9d78f89453e892006937c5e6e [file] [log] [blame]
.. title:: clang-tidy - 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 check name: ``runtime/memset``.
.. code-block:: c++
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