A new SCons release, 4.2.0, is now available on the SCons download page:


Here is a summary of the changes since 4.1.0:

NOTE: The 4.2.0 Release of SCons will deprecate Python 3.5 Support. Python 3.5 support will be dropped in the next major release.


  • Add support for the (TARGET,SOURCE,TARGETS,SOURCES,CHANGED_TARGETS,CHANGED_SOURCES}.relpath property. This will provide a path relative to the top of the build tree (where the SConstruct is located) Fixes #396
  • Added --experimental flag, to enable various experimental features/tools. You can specify 'all', 'none', or any combination of available experimental features.
  • Added affect_signature flag to _concat function. If set to False, it will prepend and append $( and $). That way the various Environment variables can use that rather than "$( _concat(...) $)".


  • Deprecate Python 3.5 as a supported version.


  • SCons now supports the command-line parameter --hash-format to override the default hash format that SCons uses. It can also be set via SetOption('hash_format'). Supported values are: md5, sha1, and sha256. For all hash formats other than the default of md5, the SConsign database will include the name of the hash format. For example, --hash-format=sha256 will create a SConsign with name .sconsign_sha256.dblite..
  • Improve Subst()'s logic to check for proper callable function or class's argument list. It will now allow callables with expected args, and any extra args as long as they have default arguments. Additionally functions with no defaults for extra arguments as long as they are set using functools.partial to create a new callable which set them.
  • Internal has_key methods removed from SCons' dictionary-like objects SubstitutionEnvironment and OverrideEnvironment - in other words, an env - to match Python 3 which no longer has dict.has_key.
  • Removed long-deprecated construction variables PDFCOM, WIN32_INSERT_DEF, WIN32DEFPREFIX, WIN32DEFSUFFIX, WIN32EXPPREFIX, WIN32EXPSUFFIX. All have been replaced by other names since at least 1.0.
  • Added CACHEDIR_CLASS construction variable and expanded CacheDir method args to support SCons invoking CacheDir derived classes for CacheDir customization. Moved copy_from_cache attribute from the Environment class to CacheDir class. Code contributed by MongoDB.
  • Update BuildTask to pass all targets to the progress object fixing an issue where multi-target build nodes only got the first target passed to the progress object.
  • Change SConscript() missing SConscript behavior - if must_exist=False, the warning is suppressed.


  • The command-line parameter --md5-chunksize is now deprecated. Use --hash-chunksize instead.
  • Fix Issue #3906 - IMPLICIT_COMMAND_DEPENDENCIES was not properly disabled when set to any string value (For example ['none','false','no','off']) Also previously 'All' wouldn't have the desired affect.
  • DocbookXslt tool: The XSLT stylesheet file is now initialized to an env.File() Node, such that dependencies work correctly in hierarchical builds (eg when using DocbookXslt in SConscript('subdir/SConscript') context.
  • The Install builder will now set the writable mode on the file(s) it copies. This restores the (previously undocumented) SCons behavior that regressed as of 4.0.0.
  • Fix issue #3790: Generators in CPPDEFINES now have access to populated source and target lists
  • Fix a potential race condition in shared cache environments where the permissions are not writeable for a moment after the file has been renamed and other builds (users) will copy it out of the cacheSmall reorganization of logic to copy files from cachedir. Moved CacheDir writeable permission code for copy to cache behind the atomic rename operation.
  • Fixed intermediate and and multi target nodes generated from SConf tests not being marked as is_conftest().

Thanks to the following contributors listed below for their contributions to this release.

git shortlog --no-merges -ns 4.1.0..HEAD
   177  William Deegan
   101  Daniel Moody
    95  Mats Wichmann
    25  Adam Gross
     4  greenbender
     4  Daniel
     4  Henrik Maier
     4  Mathew Robinson
     3  Andrew Morrow
     3  Ivan Kravets
     3  Dillan Mills
     1  WholesomeIsland
     1  dependabot[bot]
     1  djh
     1  Joseph Brill