Csmith
github.com
What it is
Csmith is a free, open-source generator of random C programs for finding compiler bugs through differential testing. Its output avoids undefined behavior and includes statistics for each generated program. A documented workflow compiles programs with GCC and Clang, then compares their outputs to identify differences. The tool can also create material for a C test suite when users do not want to write one themselves. Command-line options shown by csmith -h and csmith -hh customize random generation. Csmith runs locally on Linux and Windows. Ubuntu source builds require g++, CMake, and m4, followed by CMake and make; Windows builds are documented with Visual Studio or WSL. The project says it should build on most modern machines with a C++ compiler. Generated programs may loop indefinitely, so execution timeouts are recommended. The repository includes a COPYING license file. Bug reports and suggestions go through GitHub issues, with discussion on a mailing list; maintainers warn replies may be delayed.
Spec sheet
- Purpose
- Csmith generates random C programs to find compiler bugs using differential testing.Read 4 Oct 2026 · github.com
- Support
- The project directs users to GitHub issues for bug reports and suggestions and provides a mailing list for discussion.Read 4 Oct 2026 · github.com
- License
- The repository includes a COPYING license file.Read 4 Oct 2026 · github.com
- Build compatibility
- The INSTALL file says Csmith should build on most modern machines with a C++ compiler.Read 4 Oct 2026 · github.com
- Compiler workflow
- The README demonstrates compiling generated programs with GCC and Clang and comparing their outputs to identify compiler bugs.Read 4 Oct 2026 · github.com
- Customization
- Command-line options shown by `csmith -h` and `csmith -hh` customize random generation.Read 4 Oct 2026 · github.com
- Execution limit
- Generated programs might contain infinite loops, and the README recommends applying timeouts to their execution.Read 4 Oct 2026 · github.com
- Linux build
- The Ubuntu build instructions list g++, CMake, and m4 as prerequisites and use CMake and make to install from source.Read 4 Oct 2026 · github.com
- Origin
- Csmith was originally developed at the University of Utah as part of a compiler-testing research project and was open-sourced in 2009.Read 4 Oct 2026 · github.com
- Other use
- The project suggests using Csmith to create a C-program test suite when users do not want to write one themselves.Read 4 Oct 2026 · github.com
- Safe output
- Generated C programs are free of undefined behaviors and include per-program statistics.Read 4 Oct 2026 · github.com
- Support response
- The maintainers say they maintain Csmith in their discretionary time and responses to bug reports or feature requests may be delayed.Read 4 Oct 2026 · github.com
- Windows build
- The project documents building on Windows with Visual Studio or WSL.Read 4 Oct 2026 · github.com
Plans and prices
Csmith Free Open-source C program generator Read 4 Oct 2026 · github.com
Strong points and limits
Strong points
- Generates C programs without undefined behavior
- Includes per-program statistics
- Supports GCC and Clang output comparison
- Runs locally on Linux and Windows
- Command-line options customize generation
Limits
- Generated programs may contain infinite loops
- Linux builds require g++, CMake, and m4
- Maintainer responses may be delayed
Who it suits
Csmith suits compiler developers and testers who need generated C programs for differential testing or test suites. It is also useful when local Linux or Windows execution is preferred.
Verdict
Csmith focuses narrowly on compiler testing through generated C programs and differential comparison. It is free and configurable, but users must manage builds and apply timeouts when executing output.
Where Specifiction places it
- Fuzz Testing Software#12 of 267.8
