A new SCons release, 4.6.0, is now available on the SCons download page:


Here is a summary of the changes since 4.5.2:


  • D compilers : added support for generation of .di interface files. New variables DI_FILE_DIR, DI_FILE_DIR_PREFIX, DI_FILE_DIR_SUFFIX, DI_FILE_SUFFIX.
  • MSVC: If available, native arm64 tools will be used on arm64 hosts for VS2022.
  • MSVC: If necessary, automatically define VSCMD_SKIP_SENDTELEMETRY for VS2019 and later on arm64 hosts when using an arm (32-bit) build of python to prevent a powershell error pop-up window (powershell dll not found).
  • Add a LIBLITERALPREFIX variable which can be set to the linker's prefix for considering a library argument unmodified (e.g. for the GNU linker, the ':' in '-l:libfoo.a'). Fixes Github issue #3951.


  • When debugging (--debug=pdb), the filenames SConstruct and SConscript are now recognized when manipulating breakpoints. Previously, only a full pathname to an sconscript file worked, as pdb requires a .py extension to open a file that is not an absolute path.
  • Three unused non-public methods of the Environment Base class were dropped: get_src_sig_type, get_tgt_sig_type, _changed_source. These were unused remnants of the previously removed SourceSignatures and TargetSignatures features (dropped in 3.1.2).
  • The --debug flag now has a 'json' option which will write information generated by --debug={count, memory, time, action-timestamps} and about the build.
  • Obsoleted YACCVCGFILESUFFIX, it's being replaced by YACC_GRAPH_FILE_SUFFIX. If YACC_GRAPH_FILE_SUFFIX is not set, it will respect YACCVCGFILESUFFIX.
  • The yacc tool now understands the bison behavior of --header, --defines and --graph being called without an option-argument as being synonyms for -d (first two) and -g. -H also recognized as a synonym for -d. Default value for $YACC_GRAPH_FILE_SUFFIX changed to '.gv' to match current bison default (since bison 3.8). Set this variable to '.dot' if using byacc. Fixes #4326 and #4327.
  • MSVC: When trying to find a valid msvc batch file, the existence of the msvc compiler executable is verified for VS6 to VS2015 to avoid executing the msvc batch file when the host/target tool is known not to be present. Always check that the msvc compiler executable is found on the msvc script environment path after running the msvc batch file. This is predominately needed for recent versions of Visual Studio where the msvc batch file exists but an individual msvc toolset may not support the host/target architecture combination. For example, when using VS2022 on arm64, the arm64 native tools are only installed for the 14.3x toolsets.
  • MSVC: When the msvc compiler executable is not found during setup of the msvc environment, the warning message issued takes into account whether or not a possibly erroneous compiler executable was already present in the scons environment path. See CHANGES.txt for details.
  • Extend range of recognized Java versions to 20.
  • Builder calls (like Program()) now accept pathlib objects in source lists.
  • The Help() function now takes an additional keyword argument keep_local: when starting to build a help message, you can now retain help from AddOption calls (options added for the project, but omit help for SCons' own cmdline options with "Help(newtext, append=True, local_only=True)".
  • Calling SConscript() with a nonexistent file is now an error. Previously this succeeded - prior to SCons 3.0, silently; since 3.0, with a warning. Developers can still instruct such an SConscript() call not to fail by being explicit: pass keyword argument "must_exist=False". The "--warn=missing-sconscript" commandline option is no longer available as the warning was part of the transitional phase.
  • Add missing directories to searched paths for mingw installs
  • SCons.Util.types renamed to to SCons.Util.sctypes to avoid any possible confusion with the Python stdlib "types" module. Note that it was briefly (for 4.5.x only) possible to import directly from SCons.Util.types, although the preferred usage remains to import from SCons.Util only. Any code that did the direct import will have to change to import from SCons.Util.sctypes.
  • Add JDK 21 LTS support
  • The newly added --debug=sconscript option (new) will output notices when entering an exiting each SConscript as they are processed.


  • Fixed: when using the mingw tool, if an msys2 Python is used (os.sep is '/' rather than the Windows default ''), certain Configure checks could fail due to the construction of the path to run the compiled check.
  • C scanner's dictifyCPPDEFINES routine did not understand the possible combinations of CPPDEFINES - not aware of a "name=value" string either embedded in a sequence, or by itself. The conditional C scanner thus did not always properly apply the defines. The regular C scanner does not use these, so was not affected. [fixes #4193]
  • MSVC: The installed msvc list is calculated once and cached. There was an indirect dependency on the target architecture when determining if each version of msvc was installed based on the initial invocation. It was possible that an msvc instance would not be considered installed due to the tools for the requested target architecture not being installed. The initial call to construct the installed msvc list now uses an undefined target architecture to evaluate all potential host/target combinations when evaluating if the msvc tools are installed for a given Visual Studio installation.
  • MSVC: Erroneous construction of the installed msvc list (as described above) caused an index error in the msvc support code. An explicit check was added to prevent indexing into an empty list. Fixes #4312.
  • MSVC: The search for the msvc compiler executable (cl.exe) no longer inspects the OS system path in certain situations when setting up the msvc environment.
  • MSCommon: Test SConfTests.py would fail when mscommon debugging was enabled via the MSVC_MSCOMMON_DEBUG environment variable. The mscommon logging filter class registered with the python logging module was refactored to prevent test failure.
  • MSVS: Add arm64 to the MSVS supported architectures list for VS2017 and later to be consistent with the current documentation of MSVS_ARCH.
  • FORTRAN: Fix gfortran tool initialization. Defaults to using binary named gfortran as would be expected, and properly set's SHFORTRAN flags to include -fPIC where previously it was only doing so for the other fortran versions (F77,..)
  • MSCommon: Added more error handling while reading msvc config cache. (Enabled/specified by SCONS_CACHE_MSVC_CONFIG). The existing cache will be discarded if there's a decode error reading it. It's possible there's a race condition creating this issue it in certain CI builds.
  • Fixed: race condition in Mkdir which can happen when two SConscript are processed simultaneously by two separate build commands.


  • Now tries to find mingw if it comes from Chocolatey install of msys2.
  • MSVC: Module imports were changed from a relative import to a top-level absolute import in the following Microsoft tools: midl, mslib, mslink, mssdk, msvc, msvs. Moving any of these tools that used relative imports to the scons site tools folder would fail on import (i.e., the relative import paths become invalid when moved).


  • The build of scons now matches the help text displayed - the targets listed there can all now be given as a target to build (except for the two full source balls; the source tar.gz is currently generated directly by the GitHub release process).


  • Aligned manpage signature for Alias function to match implementation - if the previous targets parameter had been used as a keyword argument, the results would be incorrect (does not apply to positional argument usage, which had no problem).
  • Changed the message about scons -H to clarify it shows built-in options only.
  • Cachedir description updated.
  • Updated the first two chapters on building with SCons in the User Guide.
  • Clarify that exported variables are shared - if mutable, changes made in an SConscript are visible everywhere that takes a refereence to that object.
  • Update PCH builder docs with some usage notes.


  • SCons test runner now uses pathlib to normalize and compare paths to test files, which allows test lists, exclude lists, and tests on the command line to "not care" about the OS convention for pathname separators.
  • Class ActionBase is now an abstract base class to more accurately reflect its usage. Derived _ActionAction inherits the ABC, so it now declares (actually raises NotImplementedError) two methods it doesn't use so it can be instantiated by unittests and others.
  • Added more type annotations to internal routines.
  • Cleaned up dblite module (checker warnings, etc.).
  • TeX tests: skip tests that use makeindex or epstopdf not installed, or if kpsewhich glossaries.sty fails.

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

git shortlog --no-merges -ns 4.5.2..HEAD
    97  Mats Wichmann
    39  William Deegan
    20  Joseph Brill
    12  Alex Burton
     4  StenGruener
     2  Jonathon Reinhart
     2  LiuYinCarl
     2  Max Bachmann
     1  Kenshin
     1  Shohei YOSHIDA
     1  Vitaly Cheptsov