Check positive integer addition before performing it.

C: Check the upper boundary before adding two known nonnegative integers.

#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) {
    int left=INT_MAX,right=1;
    if (right>0 && left>INT_MAX-right) puts("Overflow");
    else printf("%d\n",left+right);
    return 0;
}

Expected output EXAMPLE

Overflow

Details

Save as snippet.c; compile with gcc -std=c17 -Wall -Wextra snippet.c -lm -o snippet, then run ./snippet. Check the upper boundary before adding two known nonnegative integers.

Keep in mind

This example’s inputs are nonnegative. General signed addition must also check the lower boundary.

✓ Verified

Tested on Ubuntu 24.04.5 LTS · 2026-11-02 18:02:32 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: c01d9904ae284fd35336435a7fb5b6f85b2a31de9c49072aa0f629c36ba7e970
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

Overflow

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