C++

Summary

Item	Value
API name	cpp
source OCI image	alpine:3.22 + build-base
per-job resource ceiling	1 vCPU, 512 MiB

The vCPU and RAM ceiling exists to prevent abuse; libkrun memory is elastic and the host only pays for what the guest touches.

Warmup

apk add build-base: the base image ships no compiler. The package is installed in the build VM and baked into the ext4; the job needs no network. See Images.

How the code is executed

The main file (the first in files) is compiled with g++ -o <binary> <file> and the binary is run with the job's stdin. A compilation error returns exception: "Compilation failed", with the g++ output in stderr. Everything runs in a directory under /tmp (tmpfs), in a fresh VM destroyed at the end of the job, with no network.

Building the image

rc image build --stack cpp

Example

curl -s http://127.0.0.1:8080/api/v1/run \
  -H 'Content-Type: application/json' \
  -d '{
    "language": "cpp",
    "files": [
      {"name": "main.cpp", "content": "#include <iostream>\n\nint main() {\n    int n;\n    std::cin >> n;\n    std::cout << n * 2 << std::endl;\n}\n"}
    ],
    "stdin": "21"
  }'

Expected stdout: 42.