Scons

From Joseph Brill:
- For msvc version specifications without an 'Exp' suffix, an express installation
is used when no other edition is detected for the msvc version. Similarly, an
express installation of the IDE binary is used when no other IDE edition is
detected.
- VS2015 Express (14.0Exp) does not support the sdk version argument. VS2015 Express
does not support the store argument for target architectures other than x86.
Script argument validation now takes into account these restrictions.
- VS2015 BuildTools (14.0) does not support the sdk version argument and does not
support the store argument. Script argument validation now takes into account
these restrictions.
- The Windows SDK for Windows 7 and .NET Framework 4" (SDK 7.1) populates the
registry keys in a manner in which the msvc detection would report that VS2010
(10.0) is installed when only the SDK was installed. The installed files are
intended to be used via the sdk batch file setenv.cmd. The installed msvc
batch files will fail. The msvc detection logic now ignores SDK-only VS2010
installations. Similar protection is implemented for the sdk-only installs that
populate the installation folder and registry keys for VS2008 (9.0), if necessary.
- For VS2005 (8.0) to VS2015 (14.0), vsvarsall.bat is employed to dispatch to a
dependent batch file when configuring the msvc environment. Previously, only the
existence of the compiler executable was verified. In certain installations, the
dependent batch file (e.g., vcvars64.bat) may not exist while the compiler
executable does exist resulting in build failures. The existence of vcvarsall.bat,
the dependent batch file, and the compiler executable are now validated.
- MSVC configuration data specific to versions VS2005 (8.0) to VS2008 (9.0) was added
as the dependent batch files have different names than the batch file names used
for VS2010 (10.0) and later. The VS2008 (9.0) Visual C++ For Python installation
is handled as a special case as the dependent batch files are: (a) not used and (b)
in different locations.
- When VS2008 (9.0) Visual C++ For Python is installed using the ALLUSERS=1 option
(i.e., msiexec /i VCForPython27.msi ALLUSERS=1), the registry keys are written to
HKEY_LOCAL_MACHINE rather than HKEY_CURRENT_USER. An entry was added to query the
Visual C++ For Python keys in HKLM following the HKCU query, if necessary.
- For VS2008, a full development edition (e.g., Professional) is now selected before
a Visual C++ For Python edition. Prior to this change, Visual C++ For Python was
selected before a full development edition when both editions are installed.
- The registry detection of VS2015 (14.0), and earlier, is now cached at runtime and
is only evaluated once for each msvc version.
- The vswhere executable is frozen upon initial detection. Specifying a different
vswhere executable via the construction variable VSWHERE after the initial
detection now results in an exception. Multiple bugs in the implementation of
specifying a vswhere executable via the construction variable VSWHERE have been
fixed. Previously, when a user specified vswhere executable detects new msvc
installations after the initial detection, the internal msvc installation cache
and the default msvc version based on the initial detection are no longer valid.
For example, when no vswhere executable is found for the initial detection
and then later an environment is constructed with a user specified vswhere
executable that detects new msvc installations.
- The vswhere detection of VS2017 (14.1), and later, is now cached at runtime and is
only evaluated once using a single vswhere invocation for all msvc versions.
Previously, the vswhere executable was invoked for each supported msvc version.
- The vswhere executable locations for the WinGet and Scoop package managers were
added to the default vswhere executable search list after the Chocolatey
installation location.
- Fix issue 4543: add support for msvc toolset versions 14.4X installed as the
latest msvc toolset versions for msvc buildtools v143. The v143 msvc buildtools
may contain msvc toolset versions from 14.30 to 14.4X.

From Thaddeus Crews:
- GetSConsVersion() to grab the latest SCons version without needing to
access SCons internals.
- Migrate setup.cfg logic to pyproject.toml; remove setup.cfg.
- Update .gitattributes to match .editorconfig; enforce eol settings.
- Replace black/flake8 with ruff for more efficient formatting & linting.
- When debugging (--debug=pdb), the filename SCsub is now recognized when
manipulating breakpoints.

From Raymond Li:
- Fix issue 3935: OSErrors are now no longer hidden during execution of
Actions. All exceptions during the execution of an Action are now
returned by value rather than by raising an exception, for more
consistent behavior.
NOTE: With this change, user created Actions should now catch and handle
expected exceptions (whereas previously many of these were silently
caught and suppressed by the SCons Action exection code).

From Ryan Carsten Schmidt:
- Teach ParseFlags to put a --stdlib=libname argument into CXXFLAGS.
If placed in CCFLAGS (the default location), it could be fed to the
C compiler (gcc, clang) where it is not applicable and causes a
warning message.

From Mats Wichmann:
- Updated Value Node docs and tests.
- Python 3.13 compat: re.sub deprecated count, flags as positional args,
caused update-release-info test to fail.
- Dump() with json format selected now recognizes additional compound types
(UserDict and UserList), which improves the detail of the display.
json output is also sorted, to match the default display.
- Python 3.13 (alpha) changes the behavior of isabs() on Windows. Adjust
SCons usage of in NodeInfo classes to match. Fixes 4502, 4504.
- Drop duplicated __getstate__ and __setstate__ methods in AliasNodeInfo,
FileNodeInfo and ValueNodeInfo classes, as they are identical to the
ones in parent NodeInfoBase and can just be inherited.
- Update manpage for Tools, and for TOOL, which also gets a minor
tweak for how it's handled (should be more accurate in a few situations).
- Test framework now uses a subdirectory named "scons" below the base
temporary directory. This gives something invariant to tell antivirus
to ignore without having to exclude tmpdir itself. Fixes 4509.
- MSVS "live" tests of project files adjusted to look for the generated
executable with an exe sufffix
- Documentation build now properly passes through skipping the PDF
(and EPUB) builds of manpage and user guide; this can also be done
manually if directly calling doc/man/SConstruct and doc/user/SConstruct
by adding SKIP_PDF=1. This should help with distro packaging of SCons,
which now does not need "fop" and other tools to be set up in order to
build pdf versions which are then ignored.
- Add the ability to print a Variables object for debugging purposes
(provides a __str__ method in the class).
- Mark Python 3.6 support as deprecated.
- Clean up Variables: more consistently call them variables (finish the
old change from Options) in docstrings, etc.; some typing and other
tweaks. Update manpage and user guide for Variables usage.
- Regularize internal usage of Python version strings and drop one
old Python 2-only code block in a test.
- scons-time tests now supply a "filter" argument to tarfile.extract
to quiet a warning which was added in Python 3.13 beta 1.
- Improved the conversion of a "foreign" exception from an action
into BuildError by making sure our defaults get applied even in
corner cases. Fixes 4530.
- Restructured API docs build (Sphinx) so main module contents appear
on a given page *before* the submodule docs, not after. Also
tweaked the Util package doc build so it's structured more like the
other packages (a missed part of the transition when it was split).
- Updated manpage description of Command "builder" and function.
- Framework for scons-time tests adjusted so a path with a long username
Windows has squashed doesn't get re-expanded. Fixes a problem seen
on GitHub Windows runner which uses a name "runneradmin".
- SCons.Environment.is_valid_construction_var() now returns a boolean to
match the convention that functions beginning with "is" have yes/no
answers (previously returned either None or an re.match object).
Now matches the annotation and docstring (which were prematurely
updated in 4.6). All SCons usage except unit test was already fully
consistent with a bool.
- When a variable is added to a Variables object, it can now be flagged
as "don't perform substitution" by setting the argument subst.
This allows variables to contain characters which would otherwise
cause expansion. Fixes 4241.
- The test runner now recognizes the unittest module's return code of 5,
which means no tests were run. SCons/Script/MainTests.py currently
has no tests, so this particular error code is expected - should not
cause runtest to give up with an "unknown error code".
- Updated the notes about reproducible builds with SCons and the example.
- The Clone() method now respects the variables argument (fixes 3590)
- is_valid_construction_var() (not part of the public API) moved from
SCons.Environment to SCons.Util to avoid the chance of import loops. Variables
and Environment both use the routine and Environment() uses a Variables()
object so better to move to a safer location.
- Performance tweak: the __setitem__ method of an Environment, used for
setting construction variables, now uses the string method isidentifier
to validate the name (updated from microbenchmark results).
- AddOption and the internal add_local_option which AddOption calls now
recognize a "settable" keyword argument to indicate a project-added
option can also be modified using SetOption. Fixes 3983.
NOTE: If you were using ninja and using SetOption() for ninja options
in your SConscripts prior to loading the ninja tool, you will now
see an error. The fix is to move the SetOption() to after you've loaded
the ninja tool.
- ListVariable now has a separate validator, with the functionality
that was previously part of the converter. The main effect is to
allow a developer to supply a custom validator, which previously
could be inhibited by the converter failing before the validator
is reached.
- Regularized header (copyright, licens) at top of documentation files
using SPDX.
- Updated introductory section of manual page.
- Minor cleanups in tests - drop unused "% locals()" stanzas.

From Ataf Fazledin Ahamed:
- Use of NotImplemented instead of NotImplementedError for special methods
of _ListVariable class

From Joseph Brill:
- Fix issue 2755: the msvs tool no longer writes the OS environment SCONS_HOME
value into the SCons environment when the SCONS_HOME variable already exists
in the SCons environment. Prior to this change, a valid user-defined SCons
environment value for SCONS_HOME would be overwritten with the OS environment
value of SCONS_HOME which could be None (i.e., undefined).
- Update the windows registry keys for detection of Visual Studio 2015 Express
('14.0Exp'): the VS2015 registry key ('WDExpress') appears to be different
than the registry key ('VCExpress') for earlier Visual Studio express
versions. The registry key value is relative to the installation root rather
than the VC folder and requires additional path components during evaluation.
- Fix the vs-6.0-exec.py test script: the msvs generated project is 'foo.dsp'
and the command-line invocation of the Visual Studio development environment
program was attempting to build 'test.dsp'. The command-line invocation was
changed to build 'foo.dsp'.
- Update the msvs project generation test scripts: the msvs project execution
tests could produce a "false positive" test result when the test executable is
correctly built via the SConstruct env.Program() call and the command-line
invocation of the Visual Studio development environment program fails. The
test passes due to the existence of the test executable from the initial
build. The tests were modified to delete the test executable, object file,
and sconsign file prior to the command-line invocation of the VS development
binary.
- Method unlink_files was added to the TestCmd class that unlinks a list of
files from a specified directory. An attempt to unlink a file is made only
when the file exists; otherwise, the file is ignored.
- Fix issue 4320: add an optional argument list string to configure's CheckFunc
method so that the generated function argument list matches the function's
prototype when including a header file.

From Thaddeus Crews:
- Explicitly wrap non-serializable values in json dump
- Implemented SCons.Util.sctyping as a safe means of hinting complex types. Currently
only implemented for `Executor` as a proof-of-concept.

From William Deegan:
- Fix sphinx config to handle SCons versions with post such as: 4.6.0.post1

From Michał Górny:
- Remove unnecessary dependencies on pypi packages from setup.cfg

From Sten Grüner:
- Fix of the --debug=sconscript option to return exist statements when using return
statement with stop flag enabled

From Prabhu S. Khalsa:
- Fix typo in user documentation (issue 4458)

From Andrew Morrow:
- The NewParallel scheduler is now the default, the `tm_v2` flag is removed,
and the old scheduler is opt-in under `--experimental=legacy_sched`. Additionally,
the new scheduler is now used for -j1 builds as well.
- A python interpreter with support for the `threading` package is now required,
and this is enforced on startup. SCons currently sets its minimum supported
Python to 3.6, and it was not until Python 3.7 where `threading` became
default supported. In practice, we expect most real world Python 3.6 deployments
will have `threading` support enabled, so this will not be an issue.
- CacheDir writes no longer happen within the taskmaster critical section,
and therefore can run in parallel with both other CacheDir writes and the
taskmaster DAG walk.
- The NewParallel scheduler now only adds threads as new work requiring execution
is discovered, up to the limit set by -j. This should reduce resource utilization
when the achievable parallelism in the DAG is less than the -j limit.

From Mats Wichmann:
- Add support for Python 3.13 (as of alpha 2). So far only affects
expected bytecodes in ActionTests.py.
- sconsign cleanup - remove some dead code, minor manpage tweaks.
- Be more cautious about encodings fetching command output on Windows.
Problem occurs in piped-spawn scenario, used by Configure tests.
Fixes 3529.
- Clarify/fix documentation of Scanners in User Guide and Manpage.
Fixes 4468.
- Fix bad typing in Action.py: process() and strfunction().
- Add Pseudo() to global functions, had been omitted. Fixes 4474.
- Improve handling of file data that SCons itself processes - try
harder to decode non-UTF-8 text. SCons.Util.to_Text now exists
to convert a byte stream, such as "raw" file data. Fixes 3569, 4462.
The Pseudo manpage entry was updated to provide more clarity.
- Clarify how SCons finds the project top directory, and what that is used for.
- The internal routine which implements the PyPackageDir function
would fail with an exception if called with a module which is
not found. It will now return None. Updated manpage entry and
docstring..
- Doc update: standardized on the use of a new entity &MSVC; to
describe the Microsoft C++ compiler. Update the version table slightly.
Amplified the usage of MSVC_VERSION.
- Improve SharedLibrary docs a bit.
- More consistent use of &Python; in the manpage. A few links added.
A warning about overwriting env['ENV'] and one about Configure
checks possibly not running in in no-exec mode also added.
- Update warnings module: adds docstrings, drop three unused warnings
(DeprecatedSourceCodeWarning, TaskmasterNeedsExecuteWarning,
DeprecatedMissingSConscriptWarning) add two warnings to manpage
(cache-cleanup-error, future-reserved-variable), improve unittest, tweak
Sphinx build.
- Add locking around creation of CacheDir config file. Fixes 4489.
- Clarify MergeFlags usage of a dict argument.
- SCons documentation build can now be controlled through SKIP_DOC
variable - rather than just true/false can now specify
skip none, skip all, skip pdf docs, skip api docs.

From Max Bachmann:
- Add missing directories to searched paths for mingw installs

From Joseph Brill:
- Fix issue 4312: the cached installed msvc list had an indirect dependency
on the target architecture in the environment dictionary. The first call
to construct the installed msvc list now forces the target architecture to be
undefined, constructs the installed msvc list, and then restores the original
target architecture.
Note: an indirect dependency on the VSWHERE construction variable in the
environment remains.
- Fix issue 4312: explicitly guard against an empty regular expression list
when msvc is not installed.
- When trying to find a valid msvc batch file, check that the compiler executable
(cl.exe) exists for VS6 to VS2015 to avoid executing the msvc batch file. Always
check that the compiler executable is found on the msvc script environment path
after running the msvc batch file. Only use the sdk batch files when all of the
msvc script host/target combinations have been exhausted and a valid script was
not found.
- Add ARM64 host configurations for windows and msvc.
Note: VS2013 and earlier has not been tested on ARM64.
- If necessary, automatically define VSCMD_SKIP_SENDTELEMETRY for VS2019 and later
on ARM64 hosts when using an arm32 build of python to prevent a powershell dll
not found error pop-up window.
- Fix an issue where test SConfTests.py would fail when mscommon debugging
was enabled. The mscommon debug filter class registered with the logging
module was refactored.
- Add arm64 to the MSVS supported architectures list for VS2017 and later to be
consistent with the current documentation of MSVS_ARCH.
- Fix an issue with an unhandled MissingConfiguration exception due to an msvc
registry query that returns a path that does not exist. Multiple invocation
paths were not prepared to handle the MissingConfiguration exception. The
MissingConfiguration exception type was removed.
- The MSCommon module import was 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 detection of the msvc compiler executable (cl.exe) has been modified:
* The host os environment path is no longer evaluated for the existence of the
msvc compiler executable when searching the detection dictionary.
* The existence of the msvc compiler executable is checked in the detection
dictionary and the scons ENV path before the detection dictionary is merged
into the scons ENV.
* Different warnings are produced when the msvc compiler is not detected in the
detection dictionary based on whether or not an msvc compiler was detected in
the scons ENV path (i.e., a msvc compiler executable already exists in the
user's ENV path prior to detection).
* The warning message issued when a msvc compiler executable is not found in the
detection dictionary was modified by adding the word "requested":
Old warning: "Could not find MSVC compiler 'cl'."
New warning: "Could not find requested MSVC compiler 'cl'.".
* An additonal sentence is appended to the warning message issued when an msvc
compiler executable is not found in the msvc detection dictionary and is found
in the user's ENV path prior to detection:
" A 'cl' was found on the scons ENV path which may be erroneous."

From Vitaly Cheptsov:
- Fix race condition in `Mkdir` which can happen when two `SConscript`
are processed simultaneously by two separate build commands.

From William Deegan:
- 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, being replaced by YACC_GRAPH_FILE_SUFFIX.
If YACC_GRAPH_FILE_SUFFIX is not set, it will respect YACCVCGFILESUFFIX.

From Sten Grüner
- The newly added --debug=sconscript option (new) will output notices when
entering an exiting each SConscript as they are processed.

From Philipp Maierhöfer:
- 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,..)

From Jonathon Reinhart:
- Fix another instance of `int main()` in CheckLib() causing failures
when using -Wstrict-prototypes.

From Mats Wichmann
- 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]
- Minor cleanup for ValidateOptions - docs and docstring tweaked,
add missed versionadded indicator.
- Added some typing annotations generated by a tool, to eliminate manual
work in future on things which are safe for the tool to produce.
Then manually fixed up some things related to bool that the tool did
not handly ideally. For example, simple functions which just did
"return 1" were interpreted by the tool as returning int, when bool
was really the intent. Functions/methods named like "is_*", "has_*",
"exists" are now pretty consistently marked as "-> bool".
- Simplify some code due to pylint observation: "C2801: Unnecessarily
calls dunder method __call__. Invoke instance directly."
- Python 3.9 dropped the alias base64.decodestring, deprecated since 3.1.
Only used in msvs.py. Use base64.decodebytes instead.
- 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.
- SCons test runner now uses pathlib to normalize and compare paths
to test files.
- 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.
- 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.
- Added effort to find mingw if it comes from Chocolatey install of msys2.
- Minor doc fixes: signature of Alias() now matches implementation
to avoid problem if kwargs used; case of Alias with no targets is
mentioned in text (was already shown in example); now mention that
Action([item]) does not return a ListAction - previously implied
that if arg was a list, a ListAction was *always* returned; mention
default Decider and sort the names of available decider functions,
and add a version marking. Minor fiddling with Alias.py docstrings.
- Python 3.12 support: new bytecodes for ActionTests.py, adapt to
changes to pathlib module in runtest.py (PosixPath no longer
converts slashes if given a Windows-style path). Also switch to
using `subTest` in `ActionTests`, so that we can see all 21 fails
due to bytecode changes (previously testcases aborted on the first
assert fail so we only saw seven), and use unittest asserts to
simplify complex printing stanzas.
- Added copyright headers to files in test/ that didn't have them.
- Drop three unused methods from the Environment Base class:
get_src_sig_type and get_tgt_sig_type, as well as "private"
_changed_source. These were orphaned when the long-deprecated
Source Signatures and Target Signatures were removed, these were
missed at that time.
- Remove dead code: some mocked classes in unit tests had methods
which have been removed from the Node class they're mocking,
there's no need to shadow those any more as there are no callers.
The methods are depends_on (base functionality removed in 2005)
and is_pseudeo_derived (base functionality removed in 2006). There
may well be more!
- Added pass_test() call to test/MSVC/MSVC_BATCH-spaces-targetdir.py.
It looked it was missing a more detailed check, but it should be
sufficient just to check the build worked. Renamed the fixture
dir to follow naming convention in test/MSVC overall, and added
a sconstest.skip file, also to follow convention.
- Marked some scanner methods as staticmethod.
- 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.
- The yacc tool now understands the bison behavior of --header,
--defines and --graph being called without 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. The graph file name (-g) is now generated
relative to the requested target file name, not to the source file
name, to match actual current behavior (only affects if target
explicitly requested with a different base name
than source). Docs updated. Fixes 4326 and 4327.
- Cleaned up dblite module (checker warnings, etc.).
- Some cleanup in the FortranCommon tool.
- Rewrite the internal _subproc routine - a new scons_subproc_run() now
makes use of Python's subprocess.run in a more natural way, getting
around some of the issues with attempted context manager use, fetching
output, etc. - we let the subprocess module do the hard work,
since it's well debugged and supported. _subproc is no longer
called by internal code, but remains in place in case there are builds
which call to it (even though it was never "published API").
- Changed the message about scons -H to clarify it shows built-in options.
- Improve CacheDir() Documentation.
- Release-building setup tweaked. (most of) the targets listed in
SCons' own "scons --help" now work again.
- Fix platform unit test on Windows for Py 3.12+. Fixes 4376.
- More tweaking of test framework overview (which is duplicated onto
the website, but not in the regular documentation section).
- Extend range of recognized Java versions to 20.
- Builder calls now accept PathLike objects in source lists. Fixes 4398.
- 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, but omit help for SCons' own
command-line options with "Help(newtext, append=True, local_only=True)".
- A little more code "modernization", done via "pypgrade" tool set
to "3.6 and above" setting.
- Finish the change to make calling SConscript() with a nonexistent
file an error. It has issued a warning since 3.0, with "warn instead
of fail" deprecated since 3.1. Fixes 3958.
- Minor (non-functional) cleanup of some tests, particuarly test/MSVC.
- 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 in certain CI
builds. Also add a simple filesystem-based locking protocol to try to
avoid the problem occuring.
- Update the first two chapters on building with SCons in the User Guide.
- Update docs on Export/Import - make sure mutable/immutable status has
been mentioned.
- Some cleanup to the Util package, including renaming SCons.Util.types
to SCons.Util.sctypes to avoid any possible confusion with the
Python stdlib types module.
- TeX tests: skip tests that use makeindex or epstopdf not installed, or
if `kpsewhich glossaries.sty` fails.
- Added a .note.GNU-stack section to the test assembler files to
avoid the GNU linker issuing warnings for its absence.
- Eliminate more http: references (mostly in comments/docstrings where
they really weren't harmful). A few links labeled dead with no alt.
- Add JDK 21 LTS support
- 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.
- Update PCH builder docs with some usage notes.

From Michał Górny:
- Remove the redundant `wheel` dependency from `pyproject.toml`,
as it is added automatically by the setuptools PEP517 backend.

From Mats Wichmann
- Fix a problem (4321) in 4.5.0/4.5.1 where ParseConfig could cause an
exception in MergeFlags when the result would be to add preprocessor
defines to existing CPPDEFINES. The following code illustrates the
circumstances that could trigger this:
env=Environment(CPPDEFINES=['a'])
env.Append(CPPDEFINES=['b'])
env.MergeFlags({'CPPDEFINES': 'c'})

From Mats Wichmann
- Fix a problem in 4.5.0 where using something like the following code
will cause a Clone()'d environment to share the CPPDEFINES with the
original Environment() which was cloned. Causing leakage of changes
to CPPDEFINES when they should be completely independent after the Clone.
env=Environment(CPPDEFINES=['a'])
env.Append(CPPDEFINES=['b']) (or AppendUnique,Prepend,PrependUnique)
env1=env.Clone()
env1.Append(CPPDEFINES=['c']) (or any other modification, but not overwriting CPPDEFINES
Now env['CPPDEFINES'] will contain 'c' when it should not.

From Anatoli Babenia:
- Do not initialize DefaultEnvironment when calling EnsureSConsVersion(),
EnsurePythonVersion(), Exit(), GetLaunchDir() and SConscriptChdir().
- Remove unused private method SConsEnvironment._exceeds_version().

From William Deegan:
- Added ValidateOptions() which will check that all command line options are in either
those specified by SCons itself, or by AddOption() in SConstruct/SConscript. It should
not be called until all AddOption() calls are completed. Resolves Issue 4187
- Refactored SCons/Taskmaster into a package. Moved SCons/Jobs.py into that package.
NOTE: If you hook into SCons.Jobs, you'll have to change that to use SCons.Taskmaster.Jobs
- Changed the Taskmaster trace logic to use python's logging module. The output formatting
should remain (mostly) the same. Minor update to unittest for this to adjust for 1 less newline.
- Migrated logging logic for --taskmastertrace to use Python's logging module. Added logging
to NewParallel Job class (Andrew Morrow's new parallel job implementation)
- Ninja: Fix execution environment sanitation for launching ninja. Previously if you set an
execution environment variable set to a python list it would crash. Now it
will create a string joining the list with os.pathsep
- Move execution environment sanitation from Action._subproc() to
SCons.Util.sanitize_shell_env(ENV)
- Moved rpm and debian directories under packaging
- Added logic to help packagers enable reproducible builds into packaging/etc/. Please
read packaging/etc/README.txt if you are interested.
- Added --experimental=tm_v2, which enables Andrew Morrow's new NewParallel Job implementation.
This should scale much better for highly parallel builds. You can also enable this via SetOption().
- Fixed command line argument --diskcheck: previously a value of 'none' was ignored.
SetOption('diskcheck','none') is unaffected, as it did not have the problem.
- Added overrides argument to SCons.Subst.scons_subst(), subst_list(), subst(), and Action's process(),
strfunction(). This allows passing a dictionary of envvars to override when evaluating subst()'d strings/lists
- Fixed Issue 4275 - when outputting compilation db and TEMPFILE was in use, the compilation db would have
command lines using the generated tempfile for long command lines, instead of the full command line for
the compilation step for the source/target pair.
- Renamed the qt tools to qt3 since the logic in that tool is only for QT version 3. Renamed all env vars
which affect qt3 from QT_ to QT3_. If you are still using SCons to build QT 3 code, you'll need to update
your SConscripts. Note that using 'qt' tool has been deprecated for some time.

From David H:
- Added JAVAPROCESSORPATH construction variable which populates -processorpath.
- Updated JavaScanner to scan JAVAPROCESSORPATH.

From Nickolai Korshunov
- Added FILE_ENCODING, to allow explicitly setting the text encoding for files
written by the Textfile() and Substfile() builders. If not specified, Textfile() and Substfile() builders
will write files as UTF-8. Fixed Issue 4302.

From Dan Mezhiborsky:
- Add newline to end of compilation db (compile_commands.json).

From Daniel Moody:
- Added error message to handle the case when SCons attempts to retrieve all the targets
for a specified builder from the CacheDir, fails to do so, and then runs into an error
when deleting the files which were retrieved. Previously if this happened there was no
errors or warnings.
- Fix issue 2757, where Configure checks that perform a check which reads a modified source
(including program, source or header file(s)) would incorrectly mark that file "up to date" so the
actual build would not see the file as modified. Leading to incorrect incremental builds.
Now configure checks now clear node info for non conftest nodes, so they will be re-evaluated for
the real taskmaster run when the build commences.

From Andrew Morrow
- Avoid returning UniqueList for `children` and other `Executor` APIs. This type
iterates more slowly than the builtin types. Also simplify uniquer_hashables to
use an faster implementation under the assumption of ordered dictionaries.

From Ryan Saunders:
- Fixed runtest.py failure on Windows caused by excessive escaping of the path to python.exe.

From Lukas Schrangl:
- Run LaTeX after biber/bibtex only if necessary

From Flaviu Tamas:
- Added -fsanitize support to ParseFlags(). This will propagate to CCFLAGS and LINKFLAGS.

From Mats Wichmann:
- A list argument as the source to the Copy() action function is now
correctly handled by converting elements to string. Copy errors out
if asked to copy a list to an existing non-directory destination.
Both the implementation and the strfunction which prints the progress
message were adjusted. Fixes 3009.
- doc: EnsureSConsVersion, EnsurePythonVersion, Exit, GetLaunchDir and
SConscriptChdir are now listed as Global functions only; the
Environment versions still work but are not documented.
- The Java scanner processing of JAVACLASSPATH for dependencies was
changed to split on os.pathsep instead of space, to match usage of
passing a path string like "xxx:yyy:zzz". This is not portable -
passing a POSIX-style path string (with ':') won't work on Windows
(';') - which is now documented with a hint to use a list instead
to be portable. Splitting on space broke paths with embedded spaces.
Fixes 4243.
- Cleanup: make sure BoolVariable usage in tests and examples uses Python
boolean values instead of 0/1.
- Stop telling people to run "python setup.py install" in the User Guide.
Adds new content on using virtualenvs to be able to have multiple
different SCons versions available on one system.
- Added the "DefaultEnvironment(tools=[])" stanza to a number of tests
that are known to be particularly slow. It's still just a tiny
speedup, but the Windows CI had been occasionally timing out,
so maybe this helps a bit.
- Remove an extra existence check in one ninja test that caused it
to be skipped on some otherwise-valid Windows installations.
- test framework tests now pass on Linux and Windows (the latter can
still run into problems on some configurations), and automated
tests are now run on changes in this area so future problems can
be spotted.
- The single-file Util module was split into a package with a few
functional areas getting their own files - Util.py had grown to
over 2100 lines.
- Add a zipapp package of scons-local: can use SCons from a local
file which does not need unpacking.
- Additional explanations for MSVSProject and MSVSSolution builders.
- Fix a problem (present in 4.4.0 only) where a Java inner class could
not be cached because the emitted filename contained a '$' and when
looked up through a node ended up generating a Python SyntaxError
because it was passed through scons_subst().
- Have the gfortran tool do a better job of honoring user preferences
for the dialect tools (F77, F90, F03 and F09, as well as the shared-library
equivalents SHF77, SHF90, SHF03, SHF09). Previously these were
unconditionally overwritten to 'gfortran'; the change should be more
in line with expectations of how these variables should work.
Also cleaned a few Fortran tests - test behavior does not change.
- Updated MSVC documentation - adds "version added" annotations on recently
added construction variables and provides a version-mapping table.
- Add Python 3.12 support, and indicate 3.11/3.12 support in package.