A new SCons release, 4.0.0, is now available
  on the SCons download page:

          https://scons.org/pages/download.html

  Here is a summary of the changes since 3.1.2:

  NEW FUNCTIONALITY

    - Added support for scanning multiple entries in an action string if
      IMPLICIT_COMMAND_DEPENDENCIES is set to 2 or 'all'. This enables more thorough
      action scanning where every item in each command line is scanned to determine
      if it is a non-source and non-target path and added to the list of implicit dependencies
      for the target.
    - Added new module SCons.Scanner.Python to allow scanning .py files.
    - Added support for explicitly passing a name when creating Value() nodes. This may be useful
      when the value can't be converted to a string or if having a name is otherwise desirable.
    - Added a new flag called "linedraw" for the command line argument  "--tree"
      that instructs scons to use single line drawing characters to draw the dependency tree.
    - Add CompilationDatabase() builder in compilation_db tool. Contributed by MongoDB.
      Setting COMPILATIONDB_USE_ABSPATH to True|False controls whether the files are absolute or relative
      paths.  Address Issue #3693 and #3694 found during development.


  DEPRECATED FUNCTIONALITY

    - Drop support for Python 2.7. SCons will be Python 3.5+ going forward.
    - Remove deprecated SourceCode()

  CHANGED/ENHANCED EXISTING FUNCTIONALITY

    - Added check for SONAME in environment to setup symlinks correctly (Github Issue #3246)
    - Resolve Issue #3248 - Removing '-Wl,-Bsymbolic' from SHLIBVERSIONFLAGS
      NOTE: If your build depends on the above you must now add to your SHLIBVERSIONFLAGS
    - Microsoft Visual Studio - switch to using uuid module to generate GUIDs rather than hand rolled
      method using md5 directly.
      NOTE: This change affects the following builders' output. If your build depends on the output of these builders
      you will likely see a rebuild.
      * Package() (with PACKAGETYPE='msi')
      * MSVSSolution()
      * MSVSProject()
    - Improve Visual Studio solution/project generation code to add support
      for a per-variant cppflags. Intellisense can be affected by cppflags,
      this is especially important when it comes to /std:c++* which specifies
      what C++ standard version to target. SCons will append /Zc:__cplusplus
      to the project's cppflags when a /std:c++* flag is found as this is
      required for intellisense to use the C++ standard version from cppflags.
    - Allow user specified location for vswhere.exe specified by VSWHERE.
      NOTE: This must be set at the time the 'msvc' 'msvs' and/or 'mslink' tool(s) are initialized to have any effect.
    - Fixed Github Issue 3628 - Hardcoding pickle protocol to 4 (supports python 3.4+)
      and skipping Python 3.8's new pickle protocol 5 whose main advantage is for out-of-band data buffers.
      NOTE: If you used Python 3.8 with SCons 3.0.0 or above, you may get a a pickle protocol error. Remove your
      .sconsign.dblite. You will end up with a full rebuild.


  FIXES

    - Cleanup dangling symlinks before running builders (Issue #3516)
    - Fixed usage of abspath and path for RootDir objects on Windows. Previously
      env.fs.Dir("T:").abspath would return "T:\T:" and now it correctly returns "T:".
    - Fix Issue #3469 - Fixed improper reuse of temporary and compiled files by Configure when changing
      the order and/or number of tests.  This is done by using the hash of the generated temporary files
      content and (For the target files) the hash of the action.
      So where previously files would be named:
      - config_1.c, config_1.o, config_1
      The will now be named (For example)
      - conftest_68b375d16e812c43e6d72d6e93401e7c_0.c,
        conftest_68b375d16e812c43e6d72d6e93401e7c_0_5713f09fc605f46b2ab2f7950455f187.o
        or
        conftest_68b375d16e812c43e6d72d6e93401e7c_0.o
        conftest_68b375d16e812c43e6d72d6e93401e7c_0_5713f09fc605f46b2ab2f7950455f187 (for executable)

  IMPROVEMENTS

    - Improve performance of Subst by preventing unnecessary frame
      allocations by no longer defining the *Subber classes inside of their
      respective function calls.
    - Improve performance of Subst in some cases by preventing
      unnecessary calls to eval when a token is surrounded in braces
      but is not a function call.
    - Improve performance of subst by removing unnecessary recursion.

  PACKAGING

    - Resolve Issue #3451 and Issue #3450 - Rewrite SCons setup.py and packaging. Move script logic to entry points so
      package can create scripts which use the correct version of Python.

  DOCUMENTATION

    - List any significant changes to the documentation (not individual
      typo fixes, even if they're mentioned in src/CHANGES.txt to give
      the contributor credit)

  DEVELOPMENT

    - List visible changes in the way SCons is developed

  Thanks to CURLY, LARRY, and MOE for their contributions to this release.
  Contributors are listed alphabetically by their last name.

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