SCons - a software construction tool

Change Log

NOTE: The 4.0.0 release of SCons dropped Python 2.7 support. Use 3.1.2 if

Python 2.7 support is required (but note old SCons releases are unsupported).

NOTE: Since SCons 4.3.0, Python 3.6.0 or above is required.

NOTE: Python 3.6 support is deprecated and will be dropped in a future release.

python.org no longer supports 3.6 or 3.7, and will drop 3.8 in Oct. 2024.

RELEASE VERSION/DATE TO BE FILLED IN LATER

From Ruben Di Battista:

- Expose `extra_libs` kwarg in Configure checks `CheckLibWithHeader`

and 'CheckLib' and forward it downstream to `CheckLib`

From Joseph Brill:

- Added error handling when creating MSVC detection debug log file specified by

SCONS_MSCOMMON_DEBUG.

- MSVS: Added default HOST_ARCH values to sconstruct/sconscript environment for

select msvs test scripts to allow tests to run on platforms not recognized by

the msvs/msvc tool implementations. Fixes #4608.

- MSVS: Fix early exit after the first msvc version loop execution in select msvs

test scripts. Select msvs test scripts were being invoked for msvc version 8.0

only. Fixes #4609.

- MSVS: Additional minor select msvs test script fixes as a result of the msvs

tests being invoked for all msvc versions: fix vs version number for vc version

14.3, fix expected platform toolset version, add and use a default known

project GUID for some select tests, add AdditionalOptions Condition to expected

vcx project file.

- MSVS: Additional minor changes to the msvs tool as a result of the msvs tests

being invoked for all msvc versions: use environment MSVS_PROJECT_GUID when

generating project files information, fix the visual studio string for VS2015,

add .vcxproj as an expected suffix for assigning the name to the file basename.

- MSVS: Add additional msvs tests for multi-project and solution builds.

- MSVS: Check for variant directory build of MSVSSolution and adjust the source

node similar to the handling for MSVSProject. The solution was generated in

the build directory instead of the source directory. The placeholder solution

file is not generated in the build directory and the solution file is generated

in the source directory similar to the handling for project files.

Fixes #4612.

- MSVS: Add project dsp nodes to the dsw source node list in the msvs tool. This

appears to always cause the project files to be generated before the solution

files which is necessary to retrieve the project GUIDs for use in the solution

file. This does change the behavior of clean for a project generated with

auto_build_solution disabled and explicit solution generation: when the

solution files are cleaned, the project files are also cleaned. The tests for

vs 6.0-7.1 were changed accordingly.

- MSVS: Add an optional keyword argument, auto_filter_projects, to MSVSSolution.

Accepted values for auto_filter_projects are:

- None [default]: raise an exception when solution file names or nodes are

detected in the projects argument list.

- True or evaluates True: automatically remove solution file names and nodes

from the project argument list.

- False or evaluates False: leave solution file names and nodes in the project

argument list. An exception is not raised.

Solution file names and/or nodes in the project argument list cause erroneous

Project records to be produced in the generated solution file. As a

convenience, an end-user may elect to ignore solution file names and nodes in

the projects argument list rather than manually removing solution file names

and nodes from the MSVSProject return values. Resolves #4613.

- MSVS: Remove the platform specification (i.e., platform = 'win32') from select

test script environments. The platform specification appears superfluous.

- SCons C preprocessor changes:

- Preserve literals that contain valid integer substring specifications.

Previously, the integer suffix could be stripped from a symbol that contained

an integer and suffix substring.

- Update the optional integer suffixes to include the z|Z and wb|WB suffixes.

- Update the optional integer suffixes to include support for alternate

orderings of unsigned with long or long long as defined in the c/cpp

grammar.

- Update the optional integer suffixes for case insensitive specifications as

defined in the c/cpp grammar.

- Add support for binary integer constants.

- Add support for octal integer constants. Previously, octal integers were

evaluated as decimal integers. A literal zero (0) is treated as an octal

number.

- Change the attempted conversion of a define expansion from using int() to

a constant expression evaluation.

From Thaddeus Crews:

- Removed Python 3.6 support.

- Ruff/Mypy: Excluded items now synced.

- Ruff: Linter includes new rules - `FA`, `UP006`, `UP007`, and `UP037` - to

detect and upgrade legacy type-hint syntax.

- Removed "SCons.Util.sctyping.py", as the functionality can now be substituted

via top-level `from __future__ import annotations`.

- Implemented type hints for Nodes.

From William Deegan:

- Update ninja tool to use ninja.BIN_DIR to find pypi packaged ninja binary.

python ninja package version 1.11.1.2 changed the location and previous

logic no longer worked.

- Added TestSCons.NINJA_BINARY to TestSCons to centralize logic to find ninja binary

- Refactored SCons.Tool.ninja -> SCons.Tool.ninja_tool, and added alias so

env.Tool('ninja') will still work. This avoids conflicting with the pypi module ninja.

- Renamed env.Help() & Help()'s argument `keep_local` to `local_only`, previously the documentation

specified `local_only`, but the code and tests were using `keep_local`. The functionality

more closely matches local only. NOTE: It doesn't seem like any code in the wild was using

local_only as we'd not received any reports of such until PR #4606 from hedger.

- Fix Issue #2281, AddPreAction() & AddPostAction() were being ignored if no action

was specified when the Alias was initially created.

From Alex James:

- On Darwin, PermissionErrors are now handled while trying to access

/etc/paths.d. This may occur if SCons is invoked in a sandboxed

environment (such as Nix).

From Prabhu S. Khalsa:

- Fix typo in man page

From Dillan Mills:

- Fix support for short options (`-x`).

From Keith F Prussing:

- Added support for tracking beamer themes in the LaTeX scanner.

From Alex Thiessen:

- Many grammatical and spelling fixes in the documentation.

From Mats Wichmann:

- PackageVariable now does what the documentation always said it does

if the variable is used on the command line with one of the enabling

string as the value: the variable's default value is produced (previously

it always produced True in this case).

- Minor updates to test framework. The functional change is that

test.must_exist() and test.must_exist_one_of() now take an optional

'message' keyword argument which is passed on to fail_test() if

the test fails. The rest is cleanup and type annotations. Be more

careful that the returns from stderr() and stdout(), which *can*

return None, are not used without checking.

- The optparse add_option method supports an additional calling style

that is not directly described in SCons docs, but is included

by reference ("see the optparse documentation for details"):

a single arg consisting of a premade option object. Because optparse

detects that case based on seeing zero kwargs and we always

added at least one (default=) that would fail for AddOption. Fix

for consistency, but don't advertise it further - not added to

manpage synopsis/description.

- Temporary files created by TempFileMunge() are now cleaned up on

scons exit, instead of at the time they're used. Fixes #4595.

- Override environments, created when giving construction environment

keyword arguments to Builder calls (or manually, through the undocumented

Override method), were modified not to "leak" on item deletion. The item

will now not be deleted from the base environment. Override Environments

now also pretend to have a _dict attribute so that regular environment

methods don't have a problem if passed an OE instance.

- Fix a problem with compilation_db component initialization - the

entries for assembler files were not being set up correctly.

- Add clang and clang++ to the default tool search orders for POSIX

and Windows platforms. These will be searched for after gcc and g++,

respectively. Does not affect explicitly requested tool lists.

Note: on Windows, SCons currently only has builtin support for

clang, not for clang-cl, the version of the frontend that uses

cl.exe-compatible command line switches.

- Some manpage cleanup for the gettext and pdf/ps builders.

- Some clarifications in the User Guide "Environments" chapter.

- Fix nasm test for missing include file, cleanup.

- Change long-standing irritant in Environment tests - instead of using

a while loop to pull test info from a list of tests and then delete

the test, structure the test data as a list of tuples and iterate it.

- Skip running a few validation tests if the user is root and the test is

not designed to work for the root user.

- Clarify documentation of Repository() in manpage and user guide.

- Add a tag to each CacheDir to let systems ignore backing it up

(per https://bford.info/cachedir/). Update the way a CacheDir

is created, since it now has to create two files.

- The Dictionary method now has an as_dict flag. If true, Dictionary

always returns a dict. The default remains to return different

types depending on whether zero, one, or multiple construction

variable names are given.

- Update Clean and NoClean documentation.

- Make sure unknown variables from a Variables file are recognized

as such. Previously only unknowns from the command line were

recognized (issue #4645).

- A Variables object now makes available a "defaulted" attribute,

a list of variable names that were set in the environment with

their values taken from the default in the variable description

(if a variable was set to the same value as the default in one

of the input sources, it is not included in this list).

- If a build Variable is created with no aliases, the name of the

Variable is no longer listed in its aliases. Internally, the name

and aliases are considered together anyway so this should not have

any effect except for being visible to custom help text formatters.

- A build Variable is now a dataclass, with initialization moving to

the automatically provided method; the Variables class no longer

writes directly to a Variable (makes static checkers happier).

- Improved Variables documentation.

- The (optional) C Conditional Scanner now does limited macro

replacement on the contents of CPPDEFINES, to improve finding deps

that are conditionally included. Previously replacement was only

done on macro definitions found in the file being scanned.

Only object-like macros are replaced (not function-like), and

only on a whole-word basis; recursion is limited to five levels

and does not error out if that limit is reached (issue #4523).

- Minor modernization: make use of stat object's st_mode, st_mtime

and other attributes rather than indexing into stat return.

- The update-release-info test is adapted to accept changed help output

introduced in Python 3.12.8/3.13.1.

- Update the User Guide Command() example which now shows a target name

being created from '${SOURCE.base}.out' to use a valid special

attribute and to explain what's being done in the example.

- Test framework reformatted using settings from pyproject.toml.

Includes code embedded in docstrings.

- Handle case of "memoizer" as one member of a comma-separated

--debug string - this was previously missed.

From Adam Scott:

- Changed Ninja's TEMPLATE rule pool to use `install_pool` instead of

`local_pool`, hoping it will fix a race condition that can occurs when

Ninja defers to SCons to build.

RELEASE 4.8.1 - Tue, 03 Sep 2024 17:22:20 -0700

From Thaddeus Crews:

- Add explicit return types to sctypes `is_*` functions. For Python <=3.9,

the return type is simply `bool`, same as before. Python 3.10 and later

will benefit from `TypeGuard`/`TypeIs`, to produce intellisense similar

to using `isinstance` directly.

From Anthony Siegrist;

- On win32 platform, handle piped process output more robustly. Output encoding

now uses 'oem' which should be the systems default encoding for the shell where

the process is being spawned.

From Mats Wichmann:

- env.Dump() now considers the "key" positional argument to be a varargs

type (zero, one or many). However called, it returns a serialized

result that looks like a dict. Previously, only a single "key" was

accepted, and unlike the zero-args case, it was serialized to a

string containing just the value (without the key). For example, if

"print(repr(env.Dump('CC'))" previously returned "'gcc'", it will now

return "{'CC': 'gcc'}".

- Add a timeout to test/ninja/default_targets.py - it's gotten stuck on

the GitHub Windows action and taken the run to the full six hour timeout.

Usually runs in a few second, so set the timeout to 3min (120).

- SCons 4.8.0 added an `__all__` specifier at the top of the Variables

module (`Variables/__init__.py`) to control what is made available in

a star import. However, there was existing usage of doing

`from SCons.Variables import *` which expected the variable *types*

to be available. While we never advertised this usage, there's no

real reason it shouldn't keep working - add to `__all__`.

- Switch SCons build to use setuptools' supported version fetcher from

the old homegrown one.

- Improve wording of manpage "Functions and Environment Methods" section.

Make doc function signature style more consistent - tweaks to AddOption,

DefaultEnvironment and Tool,.

- Fix a problem with AppendUnique and PrependUnique where a value could

be erroneously removed due to a substring match.

- Fix handling of ListVariable when supplying a quoted choice containing

a space character (issue #4585).

RELEASE 4.8.0 - Sun, 07 Jul 2024 17:22:20 -0700

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 execution 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.

RELEASE 4.7.0 - Sun, 17 Mar 2024 17:22:20 -0700

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.

RELEASE 4.6.0 - Sun, 19 Nov 2023 17:22:20 -0700

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.

RELEASE 4.5.2 - Sun, 21 Mar 2023 14:08:29 -0700

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'})

RELEASE 4.5.1 - Mon, 06 Mar 2023 14:08:29 -0700

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.

RELEASE 4.5.0 - Sun, 05 Mar 2023 14:08:29 -0700

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.

3.12 is in alpha for this SCons release, the bytecode sequences

embedded in SCons/ActionTests.py may need to change later, but

based on what is known now, 3.12 itself should work with this release.

- Add "append" keyword argument to Configure context's CheckLib and

CheckLibWithHeader to control whether to append or prepend (issue #2767)

Also added "unique" keyword, to control whether a library is added

or not if it is already in the $LIBS construction var in the

configure context. (issue #2768).

- Completely refactored the CPPDEFINES logic in Append/AppendUnique/Prepend/PrependUnique

This change fixes the following GH Issues:

- GH Issue #3876 - Append() and AppendUnique() will handle CPPDEFINES the same

- GH Issue #4254 - Make handling tuples in CPPDEFINES consistent.

- We no longer sort the keys added to CPPDEFINES by their dictionary keys.

We take advantage that their order is now stable based on insertion order

in Python 3.5+

- Added/modifed unit and system tests to verify these changes.

RELEASE 4.4.0 - Sat, 30 Jul 2022 14:08:29 -0700

From Joseph Brill:

- Verify that a user specified msvc script (via MSVC_USE_SCRIPT) exists and raise an exception

when the user specified msvc script does not exist.

- Fix issue where if you only had mingw installed on a Windows system and no MSVC compiler, and

did not explicitly request the mingw tool, mingw tool initialization would fail and set the

default compiler to MSVC which wasn't installed, yielding broken build.

Updated mingw tool so that the generate and exists methods use the same mingw search paths

(issue #4134).

- Update the debug output written to stdout for MSVC initialization which is enabled by setting

SCONS_MSCOMMON_DEBUG=- to use the logging module. Also changed the debug output format

written to stdout to include more information about the source for each message of MSVC

initialization debugging output. A single space was added before the message for all

debugging output records written to stdout and to files.

- Refactor the data definitions for msvc configurations to allow derived data structures to be

constructed during initialization that removes the need for special case handling during

runtime execution. Special case handling of host/target combinations is eliminated and

replaced with pre-computed search lists that implicitly handle the differences between full

versions and express versions of msvc. This fixes an issue where Express versions of the MSVC

compiler were not detected due to differences in initial msvc detection and msvc batch file

determination when configuring the build environment. This could lead to build failures when

only an MSVC Express instance is installed and the MSVC version is not explicitly specified

(issue #2668 and issue #2697).

- Added MSVC_USE_SETTINGS construction variable to pass a dictionary to configure the msvc compiler

system environment as an alternative to bypassing Visual Studio autodetection entirely.

- Added MSVC_SDK_VERSION construction variable which allows building with a specific Microsoft

SDK version. This variable is used with the msvc batch file determined via autodetection subject

to validation constraints. Refer to the documentation for additional requirements and validation

details.

- Added MSVC_TOOLSET_VERSION construction variable which allows building with a specific toolset

version. This variable is used with the msvc batch file determined via autodetection subject to

validation constraints. This variable does not affect the autodetection and selection of msvc

instances. The toolset version is applied after an msvc instance is selected. This could be the

default version of msvc. Refer to the documentation for additional requirements and validation

details. Addresses issue #3265, issue #3664, and pull request #4149.

- Added MSVC_SPECTRE_LIBS construction variable which allows building with spectre-mitigated

Visual C++ libraries. This variable is used with the msvc batch file determined via autodetection

subject to validation constraints. Refer to the documentation for additional requirements and

validation details.

- Added MSVC_SCRIPT_ARGS construction variable which specifies command line arguments that are

passed to the msvc batch file determined via autodetection subject to validation constraints.

Refer to the documentation for additional requirements and validation details. Addresses

enhancement issue #4106.

- An exception is raised when MSVC_UWP_APP is enabled for Visual Studio 2013 and earlier.

Previous behavior was to silently ignore MSVC_UWP_APP when enabled for Visual Studio 2013

and earlier. Refer to the documentation for additional requirements and validation details.

MSVC_UWP_APP was extended to accept True, False, and None in addition to '1' and '0'.

- The imported system environment variable names for MSVC 7.0 and 6.0 have been changed to the

names set by their respective installers. Prior to this change, bypassing MSVC detection by

specifying the MSVC 7.0 batch file directly would fail due to using an erroneous environment

variable name. Arguments are no longer passed to the MSVC 6.0 to 7.1 batch files as no

arguments are required and could improve the effectiveness of the internal MSVC cache.

- Propagate the OS and windir environment variables from the system environment to the msvc

environment. The OS and windir environment variables are used in the MSVC 6.0 batch file

and the SDK 6.0-7.1 SetEnv.cmd batch files. Inclusion of the OS and windir environment

variables eliminates some partial paths and warnings generated by the MSVC 6.0 and SDK

6.0-7.1 batch files when the variables are not defined.

Note: Attempting to run the SDK 6.0-7.1 batch files directly via MSVC_USE_SCRIPT can lead to

build failures and/or incomplete build environments. The SDK 6.0-7.1 batch files

require delayed expansion to be enabled which is currently not supported and is

typically not enabled by default on the host system. The batch files may also require

environment variables that are not included by default in the msvc environment.

- Suppress issuing a warning when there are no installed Visual Studio instances for the default

tools configuration (issue #2813). When msvc is the default compiler because there are no

compilers installed, a build may fail due to the cl.exe command not being recognized. At

present, there is no easy way to detect during msvc initialization if the default environment

will be used later to build a program and/or library. There is no error/warning issued for the

default tools as there are legitimate SCons uses that do not require a c compiler.

- Added a global policy setting and an environment construction variable for specifying the

action to be taken when an msvc request cannot be satisfied. The available options are "error",

"exception", "warning", "warn", "ignore", and "suppress". The global policy variable may be

set and retrieved via the functions msvc_set_notfound_policy and msvc_get_notfound_policy,

respectively. These two methods may be imported from SCons.Tool.MSCommon. The environment

construction variable is MSVC_NOTFOUND_POLICY. When defined, the environment construction

variable overrides the global policy setting for a given environment. When the active policy

is "error" or "exception", an MSVCVersionNotFound exception is raised. When the active policy

is "warning" or "warn", a VisualCMissingWarning warning is issued and the constructed