Buck2 vs SCons

Buck2 is a free build system from Meta for large-scale repositories that combine multiple programming languages. It uses Starlark rules, a dynamic dependency graph, and incremental actions to support extensible builds. Its language table lists prelude rules for C/C++, Erlang, Go, Haskell, Java, Kotlin, OCaml, Python, and Rust, though usability varies by language. Build actions can run remotely through services exposing Bazel's remote execution API; the project lists BuildBarn, BuildBuddy, EngFlow, and NativeLink as compatible with its distributed compilation support. Buck2 supports filesystem watching and can integrate with Meta's optional Eden virtual filesystem. Rules are hermetic by default and missing dependencies are errors, but local-only build steps are not sandboxed. The project describes Buck2 as early-stage and says it has no stable release tag; its latest binary tag changes with repository pushes. It warns that outside users may encounter rough edges, missing features, and missing toolchains. Source and binaries are available under MIT and Apache-2.0 licenses. The project directs users to GitHub for issue reports and offers a community Discord server.

SCons is an open source software construction tool and cross-platform alternative to Make, with builds configured through Python scripts. It analyzes dependencies automatically for C, C++ and Fortran, and users can extend that analysis with their own scanners. Built-in support covers C, C++, D, Java, Fortran, Yacc, Lex, Qt, SWIG, TeX and LaTeX; more tools are available from contributed sources. Builds can run in parallel, detect changes using MD5 signatures and cache built files. SCons can also generate Microsoft Visual Studio project and solution files. It is distributed under the MIT license, which permits use, modification and redistribution without charge if the license is retained. The project recommends installing the Python wheel from PyPI with pip, and offers standalone bundles; scons-local can run without installation from a local directory. SCons 4.11.1 requires Python 3.7 or later and normally has no other dependencies. Build files execute as Python code, and SCons is not sandboxed: file operations and processes run with the user's identity. The project says its current User's Guide may have missing or incorrect material.