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Csmith
What it is
Csmith is a free tool that generates random C programs to help find compiler bugs through differential testing. Its generated programs avoid undefined behavior and include statistics for each program. A documented workflow compiles generated code with GCC and Clang, then compares the outputs to look for differences. The project also suggests using Csmith to produce material for a C-program test suite when users do not want to write one themselves. Command-line options customize generation. Csmith runs locally, with project instructions for Linux and Windows: Windows builds use Visual Studio or WSL, while Ubuntu source-build instructions list g++, CMake, and m4. The project says it should build on most modern machines with a C++ compiler. Generated programs may run into infinite loops, so the README recommends timeouts when executing them. The repository includes a COPYING license file. Bug reports and suggestions go through GitHub issues, and a mailing list is available for discussion; maintainers caution that replies may take time because they maintain the project in their discretionary time.
For and against
For
- Generated programs avoid undefined behavior.
- Per-program statistics are included.
- Documents a GCC and Clang output-comparison workflow.
- Command-line options customize generation.
- Project documents Linux and Windows builds.
Against
- Generated programs may contain infinite loops.
- Maintainer responses may be delayed.
The verdict
Csmith provides a local way to generate C programs for compiler testing and test-suite creation. Users should apply execution timeouts and allow for possible delays in maintainer responses.
Who it suits
Csmith suits compiler developers and testers who need generated C programs for differential testing or test-suite creation. It is aimed at users comfortable building and running command-line software.
Plans and prices
Csmith
Open-source C program generator
Read 4 Oct 2026 · github.com
On the record
- Build compatibility
- The INSTALL file says Csmith should build on most modern machines with a C++ compiler.github.com · read 4 Oct 2026
- Compiler workflow
- The README demonstrates compiling generated programs with GCC and Clang and comparing their outputs to identify compiler bugs.github.com · read 4 Oct 2026
- Customization
- Command-line options shown by `csmith -h` and `csmith -hh` customize random generation.github.com · read 4 Oct 2026
- Execution limit
- Generated programs might contain infinite loops, and the README recommends applying timeouts to their execution.github.com · read 4 Oct 2026
- License
- The repository includes a COPYING license file.github.com · read 4 Oct 2026
- Linux build
- The Ubuntu build instructions list g++, CMake, and m4 as prerequisites and use CMake and make to install from source.github.com · read 4 Oct 2026
- Origin
- Csmith was originally developed at the University of Utah as part of a compiler-testing research project and was open-sourced in 2009.github.com · read 4 Oct 2026
- Other use
- The project suggests using Csmith to create a C-program test suite when users do not want to write one themselves.github.com · read 4 Oct 2026
- Purpose
- Csmith generates random C programs to find compiler bugs using differential testing.github.com · read 4 Oct 2026
- Safe output
- Generated C programs are free of undefined behaviors and include per-program statistics.github.com · read 4 Oct 2026
- Support
- The project directs users to GitHub issues for bug reports and suggestions and provides a mailing list for discussion.github.com · read 4 Oct 2026
- Support response
- The maintainers say they maintain Csmith in their discretionary time and responses to bug reports or feature requests may be delayed.github.com · read 4 Oct 2026
- Windows build
- The project documents building on Windows with Visual Studio or WSL.github.com · read 4 Oct 2026
