Check an array allocation size before multiplying.

C: Compare the requested element count against SIZE_MAX divided by element size.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <stdint.h>
#include <stdbool.h>
#include <errno.h>
#include <limits.h>
#include <math.h>
#include <time.h>

int main(void) {
    size_t count=SIZE_MAX;
    if (count>SIZE_MAX/sizeof(int)) puts("Size overflow");
    else puts("Size accepted");
    return 0;
}

Expected output EXAMPLE

Size overflow

Details

Save as snippet.c; compile with gcc -std=c17 -Wall -Wextra snippet.c -lm -o snippet, then run ./snippet. Compare the requested element count against SIZE_MAX divided by element size.

✓ Verified

Tested on Ubuntu 24.04.5 LTS · 2026-11-02 18:02:34 UTC · gcc (Ubuntu 13.3.0-6ubuntu2~24.04.1) 13.3.0 · gcc 4:13.2.0-7ubuntu1

Test inputs, results and environment

The exact published code ran in a dedicated Linux test container with prepared inputs. Unprivileged snippet process, external networking disabled, read-only root filesystem, and a fresh temporary working directory. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.

Architecture / host kernel: x86_64 / 6.18.54.1-microsoft-standard-WSL2
Snippet identity / locale: uid=65534, gid=65534 (unprivileged) / C.UTF-8
Interpreter invocation: gcc -std=c17 -Wall -Wextra -Werror snippet.c -lm -o snippet && ./snippet
Container image ID: sha256:32dc2d998158b6554c99b73b533f423696a0f3e31e8cbea9db10b5eee9a2fadd
Code SHA-256: 07c50ee44061431b27fdc01505cdbf5f3fdfd8d349aa1efab1e56d80c5e6a2fa
Dependencies: gcc 4:13.2.0-7ubuntu1

Test input setup

These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.

# No input files required.

Observed standard output

Size overflow

Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.