Issue 2276: Fix use of codecs module in pre-2.3 Python versions.

[scons.git] / src / RELEASE.txt

# __COPYRIGHT__
# __FILE__ __REVISION__ __DATE__ __DEVELOPER__


                 SCons - a software construction tool

                            Release Notes


This is SCons, a tool for building software (and other files).  SCons is
implemented in Python, and its "configuration files" are actually Python
scripts, allowing you to use the full power of a real scripting language
to solve build problems.  You do not, however, need to know Python to
use SCons effectively.

So that everyone using SCons can help each other learn how to use it
more effectively, please sign up for the scons-users mailing list at:

    http://lists.sourceforge.net/lists/listinfo/scons-users



RELEASE XXX -

  Please consult the CHANGES.txt file for a list of specific changes
  since last release.

  Please note the following important changes since release 1.1.0:

    --  THE $CHANGED_SOURCES, $CHANGED_TARGETS, $UNCHANGED_SOURCES
        AND $UNCHANGED_TARGETS VARIABLES WILL BECOME RESERVED

        A future release (probably 1.3.0) will make the construction
        variable names $CHANGED_SOURCES, $CHANGED_TARGETS,
        $UNCHANGED_SOURCES and $UNCHANGED_TARGETS into reserved
        construction variable names controlled by SCons itself (like
        the current $SOURCE, $TARGETS, etc.).

        Setting these variable names in the current release will generate
        a warning but still set the variables.  When they become reserved
        variable names, they will generate a different warning message
        and attempts to set these variables will be ignored.

        SCons configurations that happen to use these variable names
        should be changed to use different variable names, in order
        to ensure that the configuration continues to work with future
        versions of SCons.

  Please note the following important changes since release 0.98.4:

    --  scons.bat NOW RETURNS THE REAL SCONS EXIT STATUS

        The scons.bat script shipped with SCons used to exit with
        a status of 1 when it detected any failed (non-zero) exit
        status from the underlying Python execution of SCons itself.
        The scons.bat script now exits with the actual status
        returned by SCons.

    --  SCONS NOW WARNS WHEN TRYING TO LINK C++ AND FORTRAN OBJECT FILES

        Some C++ toolchains do not understand Fortran runtimes and create
        unpredictable executables when linking C++ and Fortran object
        files together.  SCons now issues a warning if you try to link
        C++ and Fortran object files into the same executable:

            scons: warning: Using $CXX to link Fortran and C++ code together.
                    This may generate a buggy executable if the '/usr/bin/gcc'
                    compiler does not know how to deal with Fortran runtimes.

        The warning may be suppressed with either the --warning=no-link
        or --warning=no-fortran-cxx-mix command line options, or by
        adding either of the following lines to a SConscript file:

            SetOption('warn', 'no-link')
            SetOption('warn', 'no-fortran-cxx-mix')

  Please note the following important changes since release 0.98:

    --  SCONS NO LONGER SETS THE GNU TOOLCHAIN -fPIC FLAG IN $SHCXXFLAGS

        The GNU toolchain support in previous versions of SCons would
        add the -fPIC flag to the $SHCXXFLAGS construction variable.
        The -fPIC flag has been now been removed from the default
        $SHCXXFLAGS setting.  Instead, the $SHCXXCOM construction variable
        (the default SCons command line for compiling shared objects
        from C++ source files) has been changed to add the $SHCCFLAGS
        variable, which contains the -fPIC flag.

        This change was made in order to make the behavior of the default
        C++ compilation line including $SHCCFLAGS consistent with the
        default C compilation line including $CCFLAGS.

        This change should have no impact on configurations that use
        the default $SHCXXCOM command line.  It may have an impact on
        configurations that were using the default $SHCXXFLAGS value
        *without* the $SHCCFLAGS variable to get the -fPIC flag into a
        custom command line.  You can fix these by adding the $SHCCFLAGS
        to the custom command line.

        Adding $SHCCFLAGS is backwards compatible with older SCons
        releases, although it might cause the -fPIC flag to be repeated
        on the command line if you execute it on an older version of
        SCons that sets -fPIC in both the $SHCCLAFGS and $SHCXXFLAGS
        variables.  Duplicating the -fPIC flag on the g++ command line
        will not cause any compilation problems, but the change to the
        command line may cause SCons to rebuild object files.

    --  FORTRAN NOW COMPILES .f FILES WITH gfortran BY DEFAULT

        The Fortran Tool modules have had a major overhaul with the intent
        of making them work as-is for most configurations.  In general,
        most configurations that use default settings should not see
        any noticeable difference.

        One configuration that has changed is if you have both a gfortran
        and g77 compiler installed.  In this case, previous versions of
        SCons would, by default, use g77 by default to compile files with
        a .f suffix, while SCons 0.98.1 will use the gfortran compiler
        by default.  The old behavior may be preserved by explicitly
        initializing construction environments with the 'g77' Tool module:

            env = Environment(tools = ['g77', 'default'])
        
        The above code is backwards compatible to older versions of SCons.

        If you notice any other changes in the behavior of default
        Fortran support, please let us know so we can document them in
        these release notes for other users.

  Please note the following important changes since release 0.97.0d20071212:

    --  SUPPORT FOR PYTHON VERSIONS BEFORE 2.2 IS NOW DEPRECATED

        SCons now prints the following warning when it is run by any
        Python 1.5, 2.0 or 2.1 release or sub-release:

            scons: warning: Support for pre-2.2 Python (VERSION) is deprecated.
                If this will cause hardship, contact dev@scons.tigris.org.

        You may disable all warnings about deprecated features by adding
        the option "--warn=no-deprecated" to the command line or to the
        $SCONSFLAGS environment variable:

            $ scons --warn=no-deprecated

        Using '--warn=no-deprecated' is compatible with earlier versions
        of SCons.

        You may also, as of this version of SCons, disable all warnings
        about deprecated features by adding the following to any
        SConscript file:

            SetOption('warn', 'no-deprecated')

        You may disable only the specific warning about running under
        a deprecated Python version by adding the following to any
        SConscript file:

            SetOption('warn', 'no-python-version')

        The warning may also be suppressed on the command line:

            $ scons --warn=no-python-version

        Or by specifying the --warn=no-python-version option in the
        $SCONSFLAGS environment variable.

        Using SetOption('warn', ...), and the 'no-python-version'
        command-line option for suppressing this specific warning,
        are *not* backwards-compatible to earlier versions of SCons.

    --  THE env.Copy() METHOD IS NOW OFFICIALLY DEPRECATED

        The env.Copy() method is now officially deprecated and will
        be removed in a future release.  Using the env.Copy() method
        now generates the following message:

            scons: warning: The env.Copy() method is deprecated; use the env.Clone() method instead.

        You may disable all warnings about deprecated features by adding
        the option "--warn=no-deprecated" to the command line or to the
        $SCONSFLAGS environment variable:

            $ scons --warn=no-deprecated

        Using '--warn=no-deprecated' is compatible with earlier versions
        of SCons.

        You may also, as of this version of SCons, disable all warnings
        about deprecated features by adding the following to any
        SConscript file:

            SetOption('warn', 'no-deprecated')

        You may disable only the specific warning about the deprecated
        env.Copy() method by adding the following to any SConscript
        file:

            SetOption('warn', 'no-deprecated-copy')

        The warning may also be suppressed on the command line:

            $ scons --warn=no-deprecated-copy

        Or by specifying the --warn=no-deprecated-copy option in the
        $SCONSFLAGS environment variable.

        Using SetOption('warn', ...), and the 'no-deprecated-copy'
        command-line option for suppressing this specific warning,
        are *not* backwards-compatible to earlier versions of SCons.

    --  THE --debug=dtree, --debug=stree AND --debug=tree OPTIONS ARE DEPRECATED

        The --debug=dtree, --debug=stree and --debug=tree methods
        are now officially deprecated and will be removed in a
        future release.  Using these options now generate a warning
        message recommending use of the --tree=derived, --tree=all,status
        and --tree=all options, respectively.

        You may disable these warnings, and all warnings about
        deprecated features, by adding the option "--warn=no-deprecated"
        to the command line or to the $SCONSFLAGS environment
        variable:

            $ scons --warn=no-deprecated

        Using '--warn=no-deprecated' is compatible with earlier versions
        of SCons.

    --  THE TargetSignatures() AND SourceSignatures() FUNCTIONS ARE DEPRECATED

        The TargetSignatures() and SourceSignatures() functions,
        and their corresponding env.TargetSignatures() and
        env.SourceSignatures() methods, are now officially deprecated
        and will be be removed in a future release.  Using ahy of
        these functions or methods now generates a message
        similar to the following:

            scons: warning: The env.TargetSignatures() method is deprecated;
                    convert your build to use the env.Decider() method instead.

        You may disable all warnings about deprecated features by adding
        the option "--warn=no-deprecated" to the command line or to the
        $SCONSFLAGS environment variable:

            $ scons --warn=no-deprecated

        Using '--warn=no-deprecated' is compatible with earlier versions
        of SCons.

        You may also, as of this version of SCons, disable all warnings
        about deprecated features by adding the following to any
        SConscript file:

            SetOption('warn', 'no-deprecated')

        You may disable only the specific warning about the use of
        TargetSignatures() or SourceSignatures() by adding the
        following to any SConscript file:

            SetOption('warn', 'no-deprecated-target-signatures')
            SetOption('warn', 'no-deprecated-source-signatures')

        The warnings may also be suppressed on the command line:

            $ scons --warn=no-deprecated-target-signatures --warn=no-deprecated-source-signatures

        Or by specifying these options in the $SCONSFLAGS environment
        variable.

        Using SetOption('warn', ...), or the command-line options
        for suppressing these warnings, is *not* backwards-compatible
        to earlier versions of SCons.

    --  File(), Dir() and Entry() NOW RETURN A LIST WHEN THE INPUT IS A SEQUENCE

        Previously, if these methods were passed a list, the list was
        substituted and stringified, then passed as a single string to
        create a File/Dir/Entry Node.  This rarely if ever worked with
        more than one element in the list.  They now return a list of
        Nodes when passed a list.

        One case that works differently now is a passing in a
        single-element sequence; that formerly was stringified
        (returning its only element) and then a single Node would be
        returned.  Now a single-element list containing the Node will
        be returned, for consistency.

    --  THE env.subst() METHOD NOW RETURNS A LIST WHEN THE INPUT IS A SEQUENCE

        The env.subst() method now returns a list with the elements
        expanded when given a list as input.  Previously, the env.subst()
        method would always turn its result into a string.

        This behavior was changed because it interfered with being able
        to include things like lists within the expansion of variables
        like $CPPPATH and then have SCons understand that the elements
        of the "internal" lists still needed to be treated separately.
        This would cause a $CPPPATH list like ['subdir1', 'subdir']
        to show up in a command line as "-Isubdir1 subdir".

    --  THE Jar() BUILDER NOW USES THE Java() BUILDER CLASSDIR BY DEFAULT

        By default, the Jar() Builder will now use the class directory
        specified when the Java() builder is called.  So the following
        input:

            classes = env.Java('classes', 'src')
            env.Jar('out.jar', classes)

        Will cause "-C classes" to be passed the "jar" command invocation,
        and the Java classes in the "out.jar" file will not be prefixed
        "classes/".

        Explicitly setting the $JARCHDIR variable overrides this default
        behavior.  The old behavior of not passing any -C option to the
        "jar" command can be preserved by explicitly setting $JARCHDIR
        to None:

            env = Environment(JARCHDIR = None)

        The above setting is compatible with older versions of SCons.

  Please note the following important changes since release 0.97.0d20070918:

    --  SCons REDEFINES PYTHON open() AND file() ON Windows TO NOT PASS
        ON OPEN FILE HANDLES TO CREATED PROCESSES

        On Windows systems, SCons now redefines the Python open()
        and file() functions so that, if the Python Win32 extensions
        are available, the file handles for any opened files will *not*
        be inherited by subprocesses, such as the spawned compilers and
        other tools invoked to build the software.

        This prevents certain race conditions where a file handle for
        a file opened by Python (either in a Python function action,
        or directly in a SConscript file) could be inherited and help
        open by a subprocess, interfering with the ability of other
        processes to create or modify the file.

        In general, this should not cause problems for the vast majority
        of configurations.  The only time this would be a problem would be
        in the unlikely event that a process spawned by SCons specifically
        *expected* to use an inherited file handle opened by SCons.

        If the Python Win32 extensions are not installed or are an
        earlier version that does not have the ability to disable file
        handle inheritance, SCons will print a warning message when the
        -j option is used.  The warning message may be suppressed by
        specifying --warn=no-parallel-support.

  Please note the following important changes since release 0.97.0d20070809:

    --  "content" SIGNATURES ARE NOW THE DEFAULT BEHAVIOR

        The default behavior of SCons is now to use the MD5 checksum of
        all file contents to decide if any files have changed and should
        cause rebuilds of their source files.  This means that SCons may
        decide not to rebuild "downstream" targets if a a given input
        file is rebuilt to the exact same contents as the last time.
        The old behavior may preserved by explicity specifying:

            TargetSignatures("build")

        In any of your SConscript files.

    --  TARGETS NOW IMPLICITLY DEPEND ON THE COMMAND THAT BUILDS THEM

        For all targets built by calling external commands (such as a
        compiler or other utility), SCons now adds an implicit dependency
        on the command(s) used to build the target.

        This will cause rebuilds of all targets built by external commands
        when running SCons in a tree built by previous version of SCons,
        in order to update the recorded signatures.

        The old behavior of not having targets depend on the external
        commands that build them can be preserved by setting a new
        $IMPLICIT_COMMAND_DEPENDENCIES construction variable to a
        non-True value:

            env = Environment(IMPLICIT_COMMAND_DEPENDENCIES = 0)
        
        or by adding Ignore() calls for any targets where the behavior
        is desired:

            Ignore('/usr/bin/gcc', 'foo.o')

        Both of these settings are compatible with older versions
        of SCons.

    --  CHANGING SourceSignature() MAY CAUSE "UNECESSARY" REBUILDS

        If you change the SourceSignature() value from 'timestamp' to
        'MD5', SCons will now rebuild targets that were already up-to-date
        with respect to their source files.

        This will happen because SCons did not record the content
        signatures of the input source files when the target was last
        built--it only recorded the timestamps--and it must record them
        to make sure the signature information is correct.  However,
        the content of source files may have changed since the last
        timestamp build was performed, and SCons would not have any way to
        verify that.  (It would have had to open up the file and record
        a content signature, which is one of the things you're trying to
        avoid by specifying use of timestamps....)  So in order to make
        sure the built targets reflect the contents of the source files,
        the targets must be rebuilt.

        Change the SourceSignature() value from 'MD5' to 'timestamp'
        should correctly not rebuild target files, because the timestamp
        of the files is always recorded.

        In previous versions of SCons, changing the SourceSignature()
        value would lead to unpredictable behavior, usually including
        rebuilding targets.

    --  THE Return() FUNCTION NOW ACTUALLY RETURNS IMMEDIATELY

        The Return() function now immediately stops processing the
        SConscript file in which it appears and returns the values of the
        variables named in its arguments.  It used to continue processing
        the rest of the SConscript file, and then return the values of the
        specified variables at the point the Return() function was called.

        The old behavior may be requested by adding a "stop=False"
        keyword argument to the Return() call:

                Return('value', stop=False)

        The "stop=" keyword argument is *not* compatible with SCons
        versions 0.97.0d20070809 or earlier.

  Please note the following important changes since release 0.97:

    --  env.CacheDir() NOW ONLY AFFECTS CONSTRUCTION ENVIRONMENT TARGETS

        The env.CacheDir() method now only causes derived files to be
        retrieved from the specified cache directory for targets built
        with the specified specified construction environment ("env").

        Previously, any call to env.CacheDir() or CacheDir() would modify
        a global setting and cause all built targets to be retrieved
        from the specified cache directory.  This behavior was changed so
        that env.CacheDir() would be consistent with other construction
        environment methods, which only affect targets built with the
        specified construction environment.

        The old behavior of changing the global behavior may be preserved
        by changing any env.CacheDir() calls to:

                CacheDir('/path/to/cache/directory')

        The above change is backwards-compatible and works in all earlier
        versions of SCons that support CacheDir().

    --  INTERPRETATION OF SUFFIX-LESS SOURCE ARGUMENTS HAS CHANGED

        The interpretation of source arguments (files) without suffixes
        has changed in one specific configuration.

        Previously, if a Builder had a src_suffix specified (indicating
        that source files without suffixes should have that suffix
        appended), the suffix would only be applied to suffix-less source
        arguments if the Builder did *not* have one or more attached
        source Builders (that is, the Builder was not a "multi-stage"
        Builder).  So in the following configuration:

                build_foo = Builder(src_suffix = '.foo')
                build_bar = Builder(src_suffix = '.bar',
                                    src_builder = build_bar)

                env = Environment(BUILDERS = {
                                   'Foo' : build_foo,
                                   'Boo' : build_bar,
                                  })

                env.Foo('tgt1', 'src1')
                env.Bar('tgt2', 'src2')
        
        SCons would have expected to find a source file 'src1.foo' for the
        env.Foo() call, but a source file 'src2' for the env.Bar() call.

        This behavior has now been made consistent, so that the two
        above calls would expect source files named 'src1.foo' and
        'src2.bar', respectively.

        Note that, if genuinely desired, the old behavior of building
        from a source file without a suffix at all (when the Builder has
        a src_suffix *and* a src_builder) can be specified explicity by
        turning the string into a File Node directly:

                env.Bar('tgt2', File('src2'))

        The above use of File() is backwards-compatible and will work
        on earlier versions of SCons.

    --  THE DEFAULT EXECUTION PATH FOR Solaris HAS CHANGED

        On Solaris systems, SCons now adds the "/opt/SUNWspro/bin"
        directory to the default execution $PATH variable before the
        "/usr/ccs/bin" directory.  This was done to reflect the fact
        that /opt/SUNWspro/ is the default for SUN tools, but it may
        cause a different compiler to be used if you have compilers
        installed in both directories.

    --  GENERATED config.h FILES NOW SAY "#define HAVE_{FEATURE} 1"

        When generating a "config.h" file, SCons now defines values that
        record the existence of a feature with a "1" value:

            #define HAVE_FEATURE 1

        Instead of printing the line without a "1", as it used to:

            #define HAVE_FEATURE

        This should not cause any problems in the normal use of "#ifdef
        HAVE_{FEATURE}" statements interpreted by a C preprocessor, but
        might cause a compatibility issue if a script or other utility
        looks for an exact match of the previous text.

  Please note the following planned, future changes:

    --  THE Options OBJECT AND RELATED FUNCTIONS WILL BE DEPRECATED

        The Options object is being replaced by a new Variables
        object, which uses a new Variables.AddVariable() method
        where the previous interface used Options.AddOptions().

        Similarly, the following utility functions are being replaced
        by the following similarly-named functions:

                BoolOption()            BoolVariable()
                EnumOption()            EnumVariable()
                ListOption()            ListVariable()
                PackageOption()         PackageVariable()
                PathOption()            PathVariable()

        And also related, the options= keyword argument when creating
        construction environments with the Environment() functions is
        being replaced with a variables= keyword argument.

        In some future release a deprecation warning will be added to
        existing uses of the Options object, its methods, the above
        utility functions, and the options= keyword argument of the
        Environment() function.  At some point after the deprecation
        warning is added, the Options object, related functions and
        options= keyword argument will be removed entirely.

        You can prepare for this by changing all your uses of the Options
        object and related functions to the Variables object and the new
        function names, and changing any uses of the options= keyword
        argument to variables=.

        NOTE:  CONVERTING TO USING THE NEW Variables OBJECT OR THE
        RELATED *Variable() FUNCTIONS, OR USING THE NEW variable=
        KEYWORD ARGUMENT, IS NOT BACKWARDS COMPATIBLE TO VERSIONS OF
        SCons BEFORE 0.98.  YOUR SConscript FILES WILL NOT WORK ON
        EARLIER VERSIONS OF SCons AFTER MAKING THIS CHANGE.

        If you change SConscript files in software that you make available
        for download or otherwise distribute, other users may try to
        build your software with an earlier version of SCons that does
        not have the Variables object or related *Variable() functions.
        We recommend preparing for this in one of two ways:

            --  Make your SConscript files backwards-compatible by
                modifying your calls with  Python try:-except: blocks
                as follows:

                    try:
                        vars = Variables('custom.py', ARGUMENTS)
                        vars.AddVariables(
                            BoolVariable('WARNINGS', 'cmopile with -Wall', 1),
                            EnumVariable('DEBUG', 'debug version', 'no'
                                       allowed_values=('yes', 'no', 'full'),
                                       map={}, ignorecase=0),
                            ListVariable('SHAREDLIBS',
                                         'libraries to build shared',
                                         'all',
                                         names = list_of_libs),
                            PackageVariable('X11',
                                            'use X11 from here',
                                            '/usr/bin/X11'),
                            PathVariable('QTDIR', 'root of Qt', qtdir),
                        )
                    except NameError:
                        vars = Options('custom.py', ARGUMENTS)
                        vars.AddOptions(
                            BoolOption('WARNINGS', 'cmopile with -Wall', 1),
                            EnumOption('DEBUG', 'debug version', 'no'
                                       allowed_values=('yes', 'no', 'full'),
                                       map={}, ignorecase=0),
                            ListOption('SHAREDLIBS',
                                       'libraries to build shared',
                                       'all',
                                       names = list_of_libs),
                            PackageOption('X11',
                                          'use X11 from here',
                                          '/usr/bin/X11'),
                            PathOption('QTDIR', 'root of Qt', qtdir),
                        )

                Additionally, you can check for availability of the new
                variables= keyword argument as follows:

                    try:
                        env = Environment(variables=vars)
                    except TypeError:
                        env = Environment(options=vars)

                (Note that we plan to maintain the existing Options object
                name for some time, to ensure backwards compatibility,
                so in practice it may be easier to just continue to use
                the old name until you're reasonably sure you won't have
                people trying to build your software with versions of
                SCons earlier than 0.98.1.)

            --  Use the EnsureSConsVersion() function to provide a
                descriptive error message if your SConscript files
                are executed by an earlier version of SCons:

                    EnsureSConsVersion(0, 98, 1)

    --  THE BuildDir() METHOD AND FUNCTION WILL BE DEPRECATED

        The env.BuildDir() method and BuildDir() function are being
        replaced by the new env.VariantDir() method and VariantDir()
        function.

        In some future release a deprecation warning will be added
        to existing uses of the env.BuildDir() method and BuildDir()
        function.  At some point after the deprecation warning, the
        env.Builder() method and BuildDir() function will either
        be removed entirely or have their behavior changed.

        You can prepare for this by changing all your uses of the
        env.BuildDir() method to env.VariantDir() and uses of the
        global BuildDir() function to VariantDir().  If you use a
        named keyword argument of "build_dir" when calling
        env.BuildDir() or BuildDir():

            env.BuildDir(build_dir='opt', src_dir='src')

        The keyword must be changed to "variant_dir":

            env.VariantDir(variant_dir='opt', src_dir='src')

        NOTE:  CHANGING USES OF env.BuildDir() AND BuildDir() to
        env.VariantDir() AND VariantDir() IS NOT BACKWARDS COMPATIBLE
        TO VERSIONS OF SCons BEFORE 0.98.  YOUR SConscript FILES
        WILL NOT WORK ON EARLIER VERSIONS OF SCons AFTER MAKING
        THIS CHANGE.

        If you change SConscript files in software that you make
        available for download or otherwise distribute, other users
        may try to build your software with an earlier version of
        SCons that does not have the env.VariantDir() method or
        VariantDir() fnction.  We recommend preparing for this in
        one of two ways:

            --  Make your SConscript files backwards-compatible by
                including the following code near the beginning of your
                top-level SConstruct file:

                    import SCons.Environment
                    try:
                        SCons.Environment.Environment.VariantDir
                    except AttributeError:
                        SCons.Environment.Environment.VariantDir = \
                              SCons.Environment.Environment.BuildDir

            --  Use the EnsureSConsVersion() function to provide a
                descriptive error message if your SConscript files
                are executed by an earlier version of SCons:

                    EnsureSConsVersion(0, 98)

    --  THE SConscript() "build_dir" KEYWORD ARGUMENT WILL BE DEPRECATED

        The "build_dir" keyword argument of the SConscript function
        and env.SConscript() method are being replaced by a new
        "variant_dir" keyword argument.

        In some future release a deprecation warning will be added
        to existing uses of the SConscript()/env.SConscript()
        "build_dir" keyword argument.  At some point after the
        deprecation warning, support for this keyword argument will
        be removed entirely.

        You can prepare for this by changing all your uses of the
        SConscript()/env.SConscript() 'build_dir" keyword argument:

            SConscript('src/SConscript', build_dir='opt')

        To use the new "variant_dir" keyword argument:

            SConscript('src/SConscript', variant_dir='opt')

        NOTE:  USING THE NEW "variant_dir" KEYWORD IS NOT BACKWARDS
        COMPATIBLE TO VERSIONS OF SCons BEFORE 0.98.  YOUR SConscript
        FILES WILL NOT WORK ON EARLIER VERSIONS OF SCons AFTER
        MAKING THIS CHANGE.

        If you change SConscript files in software that you make
        available for download or otherwise distribute, other users
        may try to build your software with an earlier version of
        SCons that does not support the "variant_dir" keyword.

        If you can insist that users use a recent version of SCons
        that supports "variant_dir", we recommend using the
        EnsureSConsVersion() function to provide a descriptive error
        message if your SConscript files are executed by an earlier
        version of SCons:

                    EnsureSConsVersion(0, 98)

        If you want to make sure that your SConscript files will
        still work with earlier versions of SCons, then your best
        bet is to continue to use the "build_dir" keyword until the
        support is removed (which, in all likelihood, won't happen
        for quite some time).

    --  SCANNER NAMES HAVE BEEN DEPRECATED AND WILL BE REMOVED

        Several internal variable names in SCons.Defaults for various
        pre-made default Scanner objects have been deprecated and will
        be removed in a future revision.  In their place are several new
        global variable names that are now part of the publicly-supported
        interface:

            NEW NAME              DEPRECATED NAME
            --------              ----------------------------
            CScanner              SCons.Defaults.CScan
            DSCanner              SCons.Defaults.DScan
            SourceFileScanner     SCons.Defaults.ObjSourceScan
            ProgramScanner        SCons.Defaults.ProgScan

        Of these, only ObjSourceScan was probably used at all, to add
        new mappings of file suffixes to other scanners for use by the
        Object() Builder.  This should now be done as follows:

            SourceFileScanner.add_scanner('.x', XScanner)

    --  THE env.Copy() METHOD WILL CHANGE OR GO AWAY ENTIRELY

        The env.Copy() method (to make a copy of a construction
        environment) is being replaced by the env.Clone() method.

        As of SCons 0.98, a deprecation warning has been added to
        current uses of the env.Copy() method.  At some point in
        the future, the env.Copy() method will either be removed
        entirely or have its behavior changed.

        You can prepare for this by changing all your uses of env.Copy()
        to env.Clone(), which has the exact same calling arguments.

        NOTE:  CHANGING USES OF env.Copy() TO env.Clone() WILL MAKE
        YOUR SConscript FILES NOT WORK ON VERSIONS OF SCons BEFORE
        0.96.93.

        If you change SConscript files in software that you make
        available for download or otherwise distribute, other users
        may try to build your software with an earlier version of
        SCons that does not have the env.Clone() method.  We recommend
        preparing for this in one of two ways:

            --  Make your SConscript files backwards-compatible by
                including the following code near the beginning of your
                top-level SConstruct file:

                    import SCons.Environment
                    try:
                        SCons.Environment.Environment.Clone
                    except AttributeError:
                        SCons.Environment.Environment.Clone = \
                              SCons.Environment.Environment.Copy

            --  Use the EnsureSConsVersion() function to provide a
                descriptive error message if your SConscript files
                are executed by an earlier version of SCons:

                    EnsureSConsVersion(0, 96, 93)

  SCons is developed with an extensive regression test suite, and a
  rigorous development methodology for continually improving that suite.
  Because of this, SCons is of sufficient quality that you can use it
  for real work.

  The interfaces in release 1.0 will *not* be knowingly changed in
  any new, future 1.x release.  If an interface change should ever
  become necessary due to extraordinary circumstances, the change
  and an appropriate transition strategy will be documented in these
  RELEASE notes.

  As you use SCons, please heed the following:

    - Please report any bugs or other problems that you find to our bug
      tracker at our SourceForge project page:

      http://sourceforge.net/tracker/?func=add&group_id=30337&atid=398971

      We have a reliable bug-fixing methodology already in place and
      strive to respond to problems relatively quickly.

    - Documentation is spottier than we'd like.  You may need to dive
      into the source code to figure out how to do something.  Asking
      questions on the scons-users mailing list is also welcome.  We
      will be addressing the documentation in upcoming releases, but
      would be more than glad to have your assistance in correcting this
      problem... :-)

    - The "SCons Design" documentation on the SCons web site is very
      out of date, as we made significant changes to portions of the
      interface as we figured out what worked and what didn't during the
      extensive beta implementation.  The "SCons Design" document should
      be used only for historical purposes, or for just an extremely
      general understanding of SCons' architectural goals.

    - There may be performance issues.  Improving SCons performance
      is an ongoing priority.  If you still find the performance
      unacceptable, we would very much like to hear from you and learn
      more about your configuration so we can optimize the right things.

    - Error messages don't always exist where they'd be helpful.
      Please let us know about any errors you ran into that would
      have benefitted from a (more) descriptive message.

  KNOWN PROBLEMS IN THIS RELEASE:

    For a complete list of known problems, consult the SCons Issue Tracker
    at tigris.org:

        http://scons.tigris.org/project_issues.html

    - Support for parallel builds (-j) does not work on WIN32 systems
      prior to *official* Python release 2.2 (not 2.2 pre-releases).

      Prior to Python 2.2, there is a bug in Python's Win32
      implementation such that when a thread spawns an external command,
      it blocks all threads from running.  This breaks the SCons
      multithreading architecture used to support -j builds.

      We have included a patch file, os_spawnv_fix.diff, that you can
      use if you you want to fix your version of Python to support
      parallel builds in SCons.

    - Again, the "SCons Design" documentation on the SCons web site is
      out of date.  Take what you read there with a grain of salt.

    - On Win32 systems, you must put a space between the redirection
      characters < and >, and the specified files (or construction
      variable expansions):

        command < $SOURCE > $TARGET

      If you don't supply a space (for example, "<$SOURCE"), SCons will
      not recognize the redirection.

    - MSVC .res files are not rebuilt when icons change.

    - The -c option does not clean up .sconsign files or directories
      created as part of the build, and also does not clean up
      SideEffect files (for example, Visual Studio .pdb files).

    - When using multiple Repositories, changing the name of an include
      file can cause an old version of the file to be used.

    - There is currently no way to force use of a relative path (../*)
      for directories outside the top-level SConstruct file.

    - The Jar() Builder will, on its second or subsequent invocation,
      package up the .sconsign files that SCons uses to track signatures.
      You can work around this by using the SConsignFile() function
      to collect all of the .sconsign information into a single file
      outside of the directory being packaged by Jar().

    - SCons does not currently have a way to detect that an intermediate
      file has been corrupted from outside and should be rebuilt.

    - Unicode characters in path names do not work in all circumstances.

    - SCons does not currently automatically check out SConstruct or
      SConscript files from SCCS, RCS or BitKeeper.

    - No support yet for the following planned command-line options:

         -d -e -l --list-actions --list-derived --list-where
         -o --override -p -r -R -w --write-filenames
         -W --warn-undefined-variables



Thank you for your interest, and please let us know how we can help
improve SCons for your needs.

Steven Knight
knight at baldmt dot com
http://www.baldmt.com/~knight/

With plenty of help from the SCons Development team:
        Chad Austin
        Charles Crain
        Bill Deegan
        Steve Leblanc
        Greg Noel
        Gary Oberbrunner
        Anthony Roach
        Greg Spencer
        Christoph Wiedemann