[scons.git] / src / RELEASE.txt

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                 SCons - a software construction tool

                            Release Notes


This is a beta release of 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 0.96 - XXX

  This is the seventh beta release of SCons.  Please consult the
  CHANGES.txt file for a list of specific changes since last release.

  Please note the following important changes since release 0.95:

    - All Builder calls (both built-in like Program(), Library(),
      etc. and customer Builders) now always return a list of target
      Nodes.   If the Builder only builds one target, the Builder
      call will now return a list containing that target Node, not
      the target Node itself as it used to do.

      This change should be invisibile to most normal uses of the
      return values from Builder calls.  It will cause an error if the
      SConscript file was performing some direct manipulation of the
      returned Node value.  For example, an attempt to print the name
      of a target returned by the Object() Builder:

            target = Object('foo.c')
            # OLD WAY
            print target

      Will now need to access the first element in the list returned by
      the Object() call:

            target = Object('foo.c')
            # NEW AY
            print target[0]

      This change was introduced to make the data type returned by Builder
      calls consistent (always a list), regardless of platform or number
      of returned targets.

    - The SConsignFile() function now uses an internally-supplied
      SCons.dblite module as the default DB scheme for the .sconsign file.
      If you are using the SConsignFile() function without an explicitly
      specified dbm_module argument, this will cause all of your targets
      to be recompiled the first time you use SCons 0.96.  To preserve the
      previous behavior, specify the "anydbm" module explicitly:

          import anydbm
          SConsignFile('.sconsign_file_name', anydbm)

    - The internal format of .sconsign files has been changed.  This might
      cause warnings about "ignoring corrupt .sconsign files" and rebuilds
      when you use SCons 0.96 for the first time in a tree that was
      previously built with SCons 0.95 or earlier.

    - The scan_check function that can be supplied to a custom Scanner now
      must take two arguments, the Node to be checked and a construction
      environment.  It previously only used the Node as an argument.

    - The internal Scanner.add_skey() method no longer works for the
      default scanners, which now use construction variables to hold their
      lists of suffixes.  If you had a custom Tool specification that was
      reaching into the internals in this way to add a suffix to one of
      the following scanner, you must now add the suffix to a construction
      environment through which you plan to call the scanner, as follows:

          CScan.add_skey('.x')       => env.Append(CPPSUFFIXES = ['.x'])
          DScan.add_skey('.x')       => env.Append(DSUFFIXES = ['.x'])
          FortranScan.add_skey('.x') => env.Append(FORTRANSUFFIXES = ['.x'])

    - The internal "node_factory" keyword argument has been removed;
      the separate and more flexible "target_factory" and "source_factory"
      keywords should be used instead.

    - SCons now treats file "extensions" that contain all digits (for
      example, "file.123") as part of the file basename, for easier
      handling of version numbers in the names of shared libraries
      and other files.  Builders will now add their file extensions to
      file names specified with all-digit extensions.  If you need to
      generate a file with an all-digit extension using a Builder that
      adds a file extension, you can preserve the previous behavior by
      wrapping the file name in a File() call.

    - The behavior of the env.Append() and env.Prepend() methods has
      changed when appending a string value to a UserList, or vice versa.
      They now behave like normal Python addition of a string to
      a UserList.  Given an initialization and an env.Append() call like:

          env = Environment(VAR1=UserList(['foo']), VAR2='foo')
          env.Append(VAR1='bar', VAR2=UserList(['bar'])

      The resulting values of $VAR1 and $VAR2 will now be ['foo', 'b',
      'a', 'r'] and ['f', 'o', 'o', 'bar'], respectively.  This is because
      Python UserList objects treat strings as sequences of letters when
      adding them to the value of the UserList.

      The old behavior of yielding $VAR1 and $VAR2 values of ['foo',
      'bar'] when either variable is a UserList object now requires that
      the string variables be enclosed in a list:

          env = Environment(VAR1=UserList(['foo']), VAR2=['foo'])
          env.Append(VAR1='bar', VAR2=UserList(['bar']))

      Note that the SCons behavior when appending to normal lists has
      *not* changed, and the behavior of all of the default values that
      SCons uses to initialize all construction variables has *not*
      changed.  This change *only* affects any cases where you explicitly
      use UserList objects to initialize or append to a variable.

  Please note the following important changes since release 0.94:

    - The internal Python function used by the Zip Builder in Python
      releases 1.6 or later now compresses the resulting .zip file
      by default.  The old behavior of creating an uncompressed file
      may be preserved by setting the new ZIPCOMPRESSION construction
      variable to 0 (or zipfile.ZIP_STORED, if you import the
      underlying zipfile module).

    - The "overrides" keyword argument to calls to the Builder() function
      used to create new Builder objects has been deprecated and will
      be removed in a future release.  The items in an "overrides"
      dictionary should now be specified as keyword arguments:

          # Old way, "overrides" is a dictionary:
          Builder(action = 'cp $TDIR/$TARGET $SDIR/$SOURCE',
                  overrides = {'TDIR' : dir1, 'SDIR' : dir2})

          # New way, items are specified as keyword arguments:
          Builder(action = 'cp $TDIR/$TARGET $SDIR/$SOURCE',
                  TDIR = dir1, SDIR = dir2)

    - The meaning of some of the values of the "mode" argument to
      the SCons.Util.scons_subst() and SCons.Util.scons_subst_list()
      functions have been swapped.  The wrapper Environment.subst() and
      Environment.subst_list() methods remain completely unchanged, so
      this should have no external effect.  (We've listed the change here
      because it might cause a problem if you're reaching into the SCons
      internals and calling either of these SCons.Util functions directly.)

  Please note the following FUTURE changes that you may wish to prepare
  for:

    - When compiling with Microsoft Visual Studio, SCons currently adds
      the ATL and MFC directories to the INCLUDE and LIB environment
      variables by default.  This default behavior will be changed in
      a future release; the current plan is to change it for the 0.97
      release (next release).

      Whether or not the ATL and MFC directories are added to these
      environment variables is now controlled by a new MSVS_USE_MFC_DIRS
      *construction* variable.  Setting this variable to a non-zero
      value when you initialize an Environment will ensure that these
      directories will be included in your external path(s) even when
      the default behavior changes:

          env = Environment(MSVS_USE_MFC_DIRS = 1)

      The MSVS_USE_MFC_DIRS variable may, of course, be set to 0 (or
      None) to prevent SCons from adding the ATL and MFC directories to
      the INCLUDE and LIB environment variables.

  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 "beta" status of the release reflects that we
  still may change interfaces in future releases, which may require
  modifications to your SConscript files.  We strive to hold these
  changes to a minimum.

  Nevertheless, please heed the following disclaimers:

    - 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... :-)

      In particular, the "SCons Design" documentation on the SCons web
      site is currently out of date, as we made significant changes to
      portions of the interface as we figured out what worked and what
      didn't during implementation.

    - 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 bug tracker
    page at SourceForge:

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

    - 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 currently out of date.  Take what you read there with a
      grain of salt.

    - If a file is specified to be built in multiple ways, the last
      processed builder specification overwrites all other builders,
      without any warning.

    - 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.

    - People have reported problems with SCons not stopping a build when
      an interrupt (CTRL+C) is received.  A fix was checked in to 0.11
      that should fix this behavior on many systems, but there are
      issues with the underlying Python os.system() call that suggest
      this fix does not work on all systems or in all circumstances.
      We're working to try to find a universal solution.

    - Modifying a construction environment in a subsidiary SConscript
      file modifies the global environment.

    - 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).

    - Switching content signatures from "MD5" to "timestamp" and back
      again can cause unusual errors.  These errors can be cleared up by
      removing all .sconsign 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.

    - A stray source file in a BuildDir can prevent targets from being
      (re)built when they should.

    - SCons does not automatically rebuild LaTeX files when the file
      has an undefined reference on the first build.

    - SideEffect() files are not retrieved properly from a CacheDir(),
      and can lead to a stack trace.

    - Use of --implicit-cache with TargetSignatures('content') can,
      for some changes, not rebuild a file when necessary.

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

    - The Command() global function (specified without a construction
      environment) is broken.

    - 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
        Steve Leblanc
        Gary Oberbrunner
        Anthony Roach
        Greg Spencer
        Christoph Wiedemann