Add emacs and vim editing settings to the bottom of *.py files.
[scons.git] / src / engine / SCons / Builder.py
index b7bc1a30c24d6072b4de7117c5ed62db22af7237..0f5bc76d97c5b2988551dd2205b84e2560d3c50d 100644 (file)
@@ -3,19 +3,76 @@
 Builder object subsystem.
 
 A Builder object is a callable that encapsulates information about how
-to execute actions to create a Node (file) from other Nodes (files), and
-how to create those dependencies for tracking.
+to execute actions to create a target Node (file) from source Nodes
+(files), and how to create those dependencies for tracking.
 
-The main entry point here is the Builder() factory method.  This
-provides a procedural interface that creates the right underlying
-Builder object based on the keyword arguments supplied and the types of
-the arguments.
+The main entry point here is the Builder() factory method.  This provides
+a procedural interface that creates the right underlying Builder object
+based on the keyword arguments supplied and the types of the arguments.
 
 The goal is for this external interface to be simple enough that the
 vast majority of users can create new Builders as necessary to support
 building new types of files in their configurations, without having to
 dive any deeper into this subsystem.
 
+The base class here is BuilderBase.  This is a concrete base class which
+does, in fact, represent the Builder objects that we (or users) create.
+
+There is also a proxy that looks like a Builder:
+
+    CompositeBuilder
+
+        This proxies for a Builder with an action that is actually a
+        dictionary that knows how to map file suffixes to a specific
+        action.  This is so that we can invoke different actions
+        (compilers, compile options) for different flavors of source
+        files.
+
+Builders and their proxies have the following public interface methods
+used by other modules:
+
+    __call__()
+        THE public interface.  Calling a Builder object (with the
+        use of internal helper methods) sets up the target and source
+        dependencies, appropriate mapping to a specific action, and the
+        environment manipulation necessary for overridden construction
+        variable.  This also takes care of warning about possible mistakes
+        in keyword arguments.
+
+    add_emitter()
+        Adds an emitter for a specific file suffix, used by some Tool
+        modules to specify that (for example) a yacc invocation on a .y
+        can create a .h *and* a .c file.
+
+    add_action()
+        Adds an action for a specific file suffix, heavily used by
+        Tool modules to add their specific action(s) for turning
+        a source file into an object file to the global static
+        and shared object file Builders.
+
+There are the following methods for internal use within this module:
+
+    _execute()
+        The internal method that handles the heavily lifting when a
+        Builder is called.  This is used so that the __call__() methods
+        can set up warning about possible mistakes in keyword-argument
+        overrides, and *then* execute all of the steps necessary so that
+        the warnings only occur once.
+
+    get_name()
+        Returns the Builder's name within a specific Environment,
+        primarily used to try to return helpful information in error
+        messages.
+
+    adjust_suffix()
+    get_prefix()
+    get_suffix()
+    get_src_suffix()
+    set_src_suffix()
+        Miscellaneous stuff for handling the prefix and suffix
+        manipulation we use in turning source file names into target
+        file names.
+
 """
 
 #
@@ -43,12 +100,14 @@ dive any deeper into this subsystem.
 
 __revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"
 
-import os.path
 import UserDict
+import UserList
 
 import SCons.Action
+from SCons.Debug import logInstanceCreation
 from SCons.Errors import InternalError, UserError
 import SCons.Executor
+import SCons.Memoize
 import SCons.Node
 import SCons.Node.FS
 import SCons.Util
@@ -59,58 +118,72 @@ class _Null:
 
 _null = _Null
 
-class DictCmdGenerator:
+def match_splitext(path, suffixes = []):
+    if suffixes:
+        matchsuf = filter(lambda S,path=path: path[-len(S):] == S,
+                          suffixes)
+        if matchsuf:
+            suf = max(map(None, map(len, matchsuf), matchsuf))[1]
+            return [path[:-len(suf)], path[-len(suf):]]
+    return SCons.Util.splitext(path)
+
+class DictCmdGenerator(SCons.Util.Selector):
     """This is a callable class that can be used as a
     command generator function.  It holds on to a dictionary
     mapping file suffixes to Actions.  It uses that dictionary
     to return the proper action based on the file suffix of
     the source file."""
-    
-    def __init__(self, action_dict):
-        self.action_dict = action_dict
+
+    def __init__(self, dict=None, source_ext_match=1):
+        SCons.Util.Selector.__init__(self, dict)
+        self.source_ext_match = source_ext_match
 
     def src_suffixes(self):
-        return self.action_dict.keys()
+        return self.keys()
 
     def add_action(self, suffix, action):
         """Add a suffix-action pair to the mapping.
         """
-        self.action_dict[suffix] = action
+        self[suffix] = action
 
     def __call__(self, target, source, env, for_signature):
-        ext = None
-        for src in map(str, source):
-            my_ext = SCons.Util.splitext(src)[1]
-            if ext and my_ext != ext:
-                raise UserError("While building `%s' from `%s': Cannot build multiple sources with different extensions: %s, %s" % (repr(map(str, target)), src, ext, my_ext))
-            ext = my_ext
+        if not source:
+            return []
+
+        if self.source_ext_match:
+            suffixes = self.src_suffixes()
+            ext = None
+            for src in map(str, source):
+                my_ext = match_splitext(src, suffixes)[1]
+                if ext and my_ext != ext:
+                    raise UserError("While building `%s' from `%s': Cannot build multiple sources with different extensions: %s, %s" % (repr(map(str, target)), src, ext, my_ext))
+                ext = my_ext
+        else:
+            ext = match_splitext(str(source[0]), self.src_suffixes())[1]
 
         if not ext:
+            #return ext
             raise UserError("While building `%s': Cannot deduce file extension from source files: %s" % (repr(map(str, target)), repr(map(str, source))))
+
         try:
-            return self.action_dict[ext]
-        except KeyError:
-            # Before raising the user error, try to perform Environment
-            # substitution on the keys of action_dict.
-            s_dict = {}
-            for (k,v) in self.action_dict.items():
-                s_k = env.subst(k)
-                if s_dict.has_key(s_k):
-                    # XXX Note that we do only raise errors, when variables
-                    # point to the same suffix. If one suffix is a
-                    # literal and a variable suffix contains this literal
-                    # we don't raise an error (cause the literal 'wins')
-                    raise UserError("Ambiguous suffixes after environment substitution: %s == %s == %s" % (s_dict[s_k][0], k, s_k))
-                s_dict[s_k] = (k,v)
-            try:
-                return s_dict[ext][1]
-            except KeyError:
-                raise UserError("While building `%s': Don't know how to build a file with suffix %s." % (repr(map(str, target)), repr(ext)))
+            ret = SCons.Util.Selector.__call__(self, env, source, ext)
+        except KeyError, e:
+            raise UserError("Ambiguous suffixes after environment substitution: %s == %s == %s" % (e[0], e[1], e[2]))
+        if ret is None:
+            raise UserError("While building `%s' from `%s': Don't know how to build from a source file with suffix `%s'.  Expected a suffix in this list: %s." % \
+                            (repr(map(str, target)), repr(map(str, source)), ext, repr(self.keys())))
+        return ret
 
-    def __cmp__(self, other):
-        return cmp(self.action_dict, other.action_dict)
+class CallableSelector(SCons.Util.Selector):
+    """A callable dictionary that will, in turn, call the value it
+    finds if it can."""
+    def __call__(self, env, source):
+        value = SCons.Util.Selector.__call__(self, env, source)
+        if callable(value):
+            value = value(env, source)
+        return value
 
-class DictEmitter(UserDict.UserDict):
+class DictEmitter(SCons.Util.Selector):
     """A callable dictionary that maps file suffixes to emitters.
     When called, it finds the right emitter in its dictionary for the
     suffix of the first source file, and calls that emitter to get the
@@ -119,37 +192,69 @@ class DictEmitter(UserDict.UserDict):
     returned.
     """
     def __call__(self, target, source, env):
-        ext = SCons.Util.splitext(str(source[0]))[1]
-        if ext:
-            try:
-                emitter = self[ext]
-            except KeyError:
-                # Before raising the user error, try to perform Environment
-                # substitution on the keys of emitter_dict.
-                s_dict = {}
-                for (k,v) in self.items():
-                    s_k = env.subst(k)
-                    s_dict[s_k] = v
-                try:
-                    emitter = s_dict[ext]
-                except KeyError:
-                    emitter = None
-            if emitter:
-                target, source = emitter(target, source, env)
+        emitter = SCons.Util.Selector.__call__(self, env, source)
+        if emitter:
+            target, source = emitter(target, source, env)
+        return (target, source)
+
+class ListEmitter(UserList.UserList):
+    """A callable list of emitters that calls each in sequence,
+    returning the result.
+    """
+    def __call__(self, target, source, env):
+        for e in self.data:
+            target, source = e(target, source, env)
         return (target, source)
 
+# These are a common errors when calling a Builder;
+# they are similar to the 'target' and 'source' keyword args to builders,
+# so we issue warnings when we see them.  The warnings can, of course,
+# be disabled.
+misleading_keywords = {
+    'targets'   : 'target',
+    'sources'   : 'source',
+}
+
+class OverrideWarner(UserDict.UserDict):
+    """A class for warning about keyword arguments that we use as
+    overrides in a Builder call.
+
+    This class exists to handle the fact that a single Builder call
+    can actually invoke multiple builders.  This class only emits the
+    warnings once, no matter how many Builders are invoked.
+    """
+    def __init__(self, dict):
+        UserDict.UserDict.__init__(self, dict)
+        if __debug__: logInstanceCreation(self, 'Builder.OverrideWarner')
+        self.already_warned = None
+    def warn(self):
+        if self.already_warned:
+            return
+        for k in self.keys():
+            if misleading_keywords.has_key(k):
+                alt = misleading_keywords[k]
+                msg = "Did you mean to use `%s' instead of `%s'?" % (alt, k)
+                SCons.Warnings.warn(SCons.Warnings.MisleadingKeywordsWarning, msg)
+        self.already_warned = 1
+
 def Builder(**kw):
     """A factory for builder objects."""
     composite = None
     if kw.has_key('generator'):
         if kw.has_key('action'):
             raise UserError, "You must not specify both an action and a generator."
-        kw['action'] = SCons.Action.CommandGenerator(kw['generator'])
+        kw['action'] = SCons.Action.CommandGeneratorAction(kw['generator'], {})
         del kw['generator']
-    elif kw.has_key('action') and SCons.Util.is_Dict(kw['action']):
-        composite = DictCmdGenerator(kw['action'])
-        kw['action'] = SCons.Action.CommandGenerator(composite)
-        kw['src_suffix'] = composite.src_suffixes()
+    elif kw.has_key('action'):
+        source_ext_match = kw.get('source_ext_match', 1)
+        if kw.has_key('source_ext_match'):
+            del kw['source_ext_match']
+        if SCons.Util.is_Dict(kw['action']):
+            composite = DictCmdGenerator(kw['action'], source_ext_match)
+            kw['action'] = SCons.Action.CommandGeneratorAction(composite, {})
+            kw['src_suffix'] = composite.src_suffixes()
+        else:
+            kw['action'] = SCons.Action.Action(kw['action'])
 
     if kw.has_key('emitter'):
         emitter = kw['emitter']
@@ -164,79 +269,54 @@ def Builder(**kw):
             kw['emitter'] = EmitterProxy(var)
         elif SCons.Util.is_Dict(emitter):
             kw['emitter'] = DictEmitter(emitter)
+        elif SCons.Util.is_List(emitter):
+            kw['emitter'] = ListEmitter(emitter)
 
-    if kw.has_key('src_builder'):
-        ret = apply(MultiStepBuilder, (), kw)
-    else:
-        ret = apply(BuilderBase, (), kw)
+    result = apply(BuilderBase, (), kw)
 
-    if composite:
-        ret = CompositeBuilder(ret, composite)
+    if not composite is None:
+        result = CompositeBuilder(result, composite)
 
-    return ret
+    return result
 
-def _init_nodes(builder, env, overrides, tlist, slist):
-    """Initialize lists of target and source nodes with all of
-    the proper Builder information.
+def _node_errors(builder, env, tlist, slist):
+    """Validate that the lists of target and source nodes are
+    legal for this builder and environment.  Raise errors or
+    issue warnings as appropriate.
     """
 
     # First, figure out if there are any errors in the way the targets
     # were specified.
     for t in tlist:
         if t.side_effect:
-            raise UserError, "Multiple ways to build the same target were specified for: %s" % str(t)
-        if t.has_builder():
-            if t.env != env:
-                raise UserError, "Two different environments were specified for the same target: %s"%str(t)
-            elif t.overrides != overrides:
-                raise UserError, "Two different sets of overrides were specified for the same target: %s"%str(t)
-            elif builder.scanner and builder.scanner != t.target_scanner:
-                raise UserError, "Two different scanners were specified for the same target: %s"%str(t)
-
+            raise UserError, "Multiple ways to build the same target were specified for: %s" % t
+        if t.has_explicit_builder():
+            if not t.env is None and not t.env is env:
+                action = t.builder.action
+                t_contents = action.get_contents(tlist, slist, t.env)
+                contents = action.get_contents(tlist, slist, env)
+
+                if t_contents == contents:
+                    msg = "Two different environments were specified for target %s,\n\tbut they appear to have the same action: %s" % (t, action.genstring(tlist, slist, t.env))
+                    SCons.Warnings.warn(SCons.Warnings.DuplicateEnvironmentWarning, msg)
+                else:
+                    msg = "Two environments with different actions were specified for the same target: %s" % t
+                    raise UserError, msg
             if builder.multi:
                 if t.builder != builder:
-                    if isinstance(t.builder, ListBuilder) and isinstance(builder, ListBuilder) and t.builder.builder == builder.builder:
-                        raise UserError, "Two different target sets have a target in common: %s"%str(t)
-                    else:
-                        raise UserError, "Two different builders (%s and %s) were specified for the same target: %s"%(t.builder.get_name(env), builder.get_name(env), str(t))
+                    msg = "Two different builders (%s and %s) were specified for the same target: %s" % (t.builder.get_name(env), builder.get_name(env), t)
+                    raise UserError, msg
+                # TODO(batch):  list constructed each time!
+                if t.get_executor().get_all_targets() != tlist:
+                    msg = "Two different target lists have a target in common: %s  (from %s and from %s)" % (t, map(str, t.get_executor().get_all_targets()), map(str, tlist))
+                    raise UserError, msg
             elif t.sources != slist:
-                raise UserError, "Multiple ways to build the same target were specified for: %s" % str(t)
+                msg = "Multiple ways to build the same target were specified for: %s  (from %s and from %s)" % (t, map(str, t.sources), map(str, slist))
+                raise UserError, msg
 
-    # The targets are fine, so find or make the appropriate Executor to
-    # build this particular list of targets from this particular list of
-    # sources.
-    executor = None
-    if builder.multi:
-        try:
-            executor = tlist[0].get_executor(create = 0)
-        except AttributeError:
-            pass
-        else:
-            executor.add_sources(slist)
-    if executor is None:
-        executor = SCons.Executor.Executor(builder,
-                                           tlist[0].generate_build_env(env),
-                                           overrides,
-                                           tlist,
-                                           slist)
-
-    # Now set up the relevant information in the target Nodes themselves.
-    for t in tlist:
-        t.overrides = overrides
-        t.cwd = SCons.Node.FS.default_fs.getcwd()
-        t.builder_set(builder)
-        t.env_set(env)
-        t.add_source(slist)
-        t.set_executor(executor)
-        if builder.scanner:
-            t.target_scanner = builder.scanner
-
-    # Last, add scanners from the Environment to the source Nodes.
-    for s in slist:
-        src_key = s.scanner_key()        # the file suffix
-        scanner = env.get_scanner(src_key)
-        if scanner:
-            s.source_scanner = scanner
+    if builder.single_source:
+        if len(slist) > 1:
+            raise UserError, "More than one source given for single-source builder: targets=%s sources=%s" % (map(str,tlist), map(str,slist))
 
 class EmitterProxy:
     """This is a callable class that can act as a
@@ -254,13 +334,16 @@ class EmitterProxy:
         # Recursively substitute the variable.
         # We can't use env.subst() because it deals only
         # in strings.  Maybe we should change that?
-        while SCons.Util.is_String(emitter) and \
-              env.has_key(emitter):
+        while SCons.Util.is_String(emitter) and env.has_key(emitter):
             emitter = env[emitter]
-        if not callable(emitter):
-            return (target, source)
+        if callable(emitter):
+            target, source = emitter(target, source, env)
+        elif SCons.Util.is_List(emitter):
+            for e in emitter:
+                target, source = e(target, source, env)
+
+        return (target, source)
 
-        return emitter(target, source, env)
 
     def __cmp__(self, other):
         return cmp(self.var, other.var)
@@ -270,33 +353,79 @@ class BuilderBase:
     nodes (files) from input nodes (files).
     """
 
+    if SCons.Memoize.use_memoizer:
+        __metaclass__ = SCons.Memoize.Memoized_Metaclass
+
+    memoizer_counters = []
+
     def __init__(self,  action = None,
                         prefix = '',
                         suffix = '',
                         src_suffix = '',
-                        node_factory = SCons.Node.FS.default_fs.File,
                         target_factory = None,
                         source_factory = None,
-                        scanner = None,
+                        target_scanner = None,
+                        source_scanner = None,
                         emitter = None,
                         multi = 0,
                         env = None,
-                        overrides = {}):
-        self.action = SCons.Action.Action(action)
+                        single_source = 0,
+                        name = None,
+                        chdir = _null,
+                        is_explicit = 1,
+                        src_builder = None,
+                        ensure_suffix = False,
+                        **overrides):
+        if __debug__: logInstanceCreation(self, 'Builder.BuilderBase')
+        self._memo = {}
+        self.action = action
         self.multi = multi
+        if SCons.Util.is_Dict(prefix):
+            prefix = CallableSelector(prefix)
         self.prefix = prefix
-        self.suffix = suffix
+        if SCons.Util.is_Dict(suffix):
+            suffix = CallableSelector(suffix)
         self.env = env
+        self.single_source = single_source
+        if overrides.has_key('overrides'):
+            SCons.Warnings.warn(SCons.Warnings.DeprecatedWarning,
+                "The \"overrides\" keyword to Builder() creation has been deprecated;\n" +\
+                "\tspecify the items as keyword arguments to the Builder() call instead.")
+            overrides.update(overrides['overrides'])
+            del overrides['overrides']
+        if overrides.has_key('scanner'):
+            SCons.Warnings.warn(SCons.Warnings.DeprecatedWarning,
+                                "The \"scanner\" keyword to Builder() creation has been deprecated;\n"
+                                "\tuse: source_scanner or target_scanner as appropriate.")
+            del overrides['scanner']
         self.overrides = overrides
 
+        self.set_suffix(suffix)
         self.set_src_suffix(src_suffix)
+        self.ensure_suffix = ensure_suffix
 
-        self.target_factory = target_factory or node_factory
-        self.source_factory = source_factory or node_factory
-        self.scanner = scanner
+        self.target_factory = target_factory
+        self.source_factory = source_factory
+        self.target_scanner = target_scanner
+        self.source_scanner = source_scanner
 
         self.emitter = emitter
 
+        # Optional Builder name should only be used for Builders
+        # that don't get attached to construction environments.
+        if name:
+            self.name = name
+        self.executor_kw = {}
+        if not chdir is _null:
+            self.executor_kw['chdir'] = chdir
+        self.is_explicit = is_explicit
+
+        if src_builder is None:
+            src_builder = []
+        elif not SCons.Util.is_List(src_builder):
+            src_builder = [ src_builder ]
+        self.src_builder = src_builder
+
     def __nonzero__(self):
         raise InternalError, "Do not test for the Node.builder attribute directly; use Node.has_builder() instead"
 
@@ -305,63 +434,70 @@ class BuilderBase:
 
         Look at the BUILDERS variable of env, expecting it to be a
         dictionary containing this Builder, and return the key of the
-        dictionary."""
+        dictionary.  If there's no key, then return a directly-configured
+        name (if there is one) or the name of the class (by default)."""
 
         try:
             index = env['BUILDERS'].values().index(self)
             return env['BUILDERS'].keys()[index]
-        except (AttributeError, KeyError, ValueError):
-            return str(self.__class__)
+        except (AttributeError, KeyError, TypeError, ValueError):
+            try:
+                return self.name
+            except AttributeError:
+                return str(self.__class__)
 
     def __cmp__(self, other):
         return cmp(self.__dict__, other.__dict__)
 
-    def splitext(self, path):
-        return SCons.Util.splitext(path)
-
-    def _create_nodes(self, env, overrides, target = None, source = None):
+    def splitext(self, path, env=None):
+        if not env:
+            env = self.env
+        if env:
+            suffixes = self.src_suffixes(env)
+        else:
+            suffixes = []
+        return match_splitext(path, suffixes)
+
+    def _adjustixes(self, files, pre, suf, ensure_suffix=False):
+        if not files:
+            return []
+        result = []
+        if not SCons.Util.is_List(files):
+            files = [files]
+
+        for f in files:
+            if SCons.Util.is_String(f):
+                f = SCons.Util.adjustixes(f, pre, suf, ensure_suffix)
+            result.append(f)
+        return result
+
+    def _create_nodes(self, env, target = None, source = None):
         """Create and return lists of target and source nodes.
         """
-        def adjustixes(files, pre, suf, self=self):
-            if not files:
-                return []
-            ret = []
-            if not SCons.Util.is_List(files):
-                files = [files]
-
-            for f in files:
-                if SCons.Util.is_String(f):
-                    if pre:
-                        path, fn = os.path.split(os.path.normpath(f))
-                        if fn[:len(pre)] != pre:
-                            f = os.path.join(path, pre + fn)
-                    # Only append a suffix if the file does not have one.
-                    if suf and not self.splitext(f)[1]:
-                        if f[-len(suf):] != suf:
-                            f = f + suf
-                ret.append(f)
-            return ret
-
-        env = env.Override(overrides)
-
-        pre = self.get_prefix(env)
-        suf = self.get_suffix(env)
         src_suf = self.get_src_suffix(env)
 
-        source = adjustixes(source, None, src_suf)
+        target_factory = env.get_factory(self.target_factory)
+        source_factory = env.get_factory(self.source_factory)
+
+        source = self._adjustixes(source, None, src_suf)
+        slist = env.arg2nodes(source, source_factory)
+
+        pre = self.get_prefix(env, slist)
+        suf = self.get_suffix(env, slist)
+
         if target is None:
-            s = source[0]
-            if isinstance(s, SCons.Node.Node):
-                s = str(s)
-            dir, s = os.path.split(s)
-            target = pre + self.splitext(s)[0] + suf
-            if dir:
-                target = [ os.path.join(dir, target) ]
+            try:
+                t_from_s = slist[0].target_from_source
+            except AttributeError:
+                raise UserError("Do not know how to create a target from source `%s'" % slist[0])
+            except IndexError:
+                tlist = []
+            else:
+                splitext = lambda S,self=self,env=env: self.splitext(S,env)
+                tlist = [ t_from_s(pre, suf, splitext) ]
         else:
-            target = adjustixes(target, pre, suf)
-
-        slist = SCons.Node.arg2nodes(source, self.source_factory)
-        tlist = SCons.Node.arg2nodes(target, self.target_factory)
+            target = self._adjustixes(target, pre, suf, self.ensure_suffix)
+            tlist = env.arg2nodes(target, target_factory, target=target, source=source)
 
         if self.emitter:
             # The emitter is going to do str(node), but because we're
@@ -372,70 +508,159 @@ class BuilderBase:
             new_targets = []
             for t in tlist:
                 if not t.is_derived():
-                    t.builder = self
+                    t.builder_set(self)
                     new_targets.append(t)
-        
+
+            orig_tlist = tlist[:]
+            orig_slist = slist[:]
+
             target, source = self.emitter(target=tlist, source=slist, env=env)
 
             # Now delete the temporary builders that we attached to any
-            # new targets, so that _init_nodes() doesn't do weird stuff
+            # new targets, so that _node_errors() doesn't do weird stuff
             # to them because it thinks they already have builders.
             for t in new_targets:
                 if t.builder is self:
                     # Only delete the temporary builder if the emitter
                     # didn't change it on us.
-                    t.builder = None
+                    t.builder_set(None)
 
             # Have to call arg2nodes yet again, since it is legal for
             # emitters to spit out strings as well as Node instances.
-            slist = SCons.Node.arg2nodes(source, self.source_factory)
-            tlist = SCons.Node.arg2nodes(target, self.target_factory)
+            tlist = env.arg2nodes(target, target_factory,
+                                  target=orig_tlist, source=orig_slist)
+            slist = env.arg2nodes(source, source_factory,
+                                  target=orig_tlist, source=orig_slist)
 
         return tlist, slist
 
-    def __call__(self, env, target = None, source = _null, **overrides):
-        if source is _null:
-            source = target
-            target = None
-        tlist, slist = self._create_nodes(env, overrides, target, source)
+    def _execute(self, env, target, source, overwarn={}, executor_kw={}):
+        # We now assume that target and source are lists or None.
+        if self.src_builder:
+            source = self.src_builder_sources(env, source, overwarn)
 
-        if len(tlist) == 1:
-            _init_nodes(self, env, overrides, tlist, slist)
-            tlist = tlist[0]
-        else:
-            _init_nodes(ListBuilder(self, env, tlist), env, overrides, tlist, slist)
+        if self.single_source and len(source) > 1 and target is None:
+            result = []
+            if target is None: target = [None]*len(source)
+            for tgt, src in zip(target, source):
+                if not tgt is None: tgt = [tgt]
+                if not src is None: src = [src]
+                result.extend(self._execute(env, tgt, src, overwarn))
+            return SCons.Node.NodeList(result)
+
+        overwarn.warn()
+
+        tlist, slist = self._create_nodes(env, target, source)
 
-        return tlist
+        # Check for errors with the specified target/source lists.
+        _node_errors(self, env, tlist, slist)
+
+        # The targets are fine, so find or make the appropriate Executor to
+        # build this particular list of targets from this particular list of
+        # sources.
+
+        executor = None
+        key = None
+
+        if self.multi:
+            try:
+                executor = tlist[0].get_executor(create = 0)
+            except (AttributeError, IndexError):
+                pass
+            else:
+                executor.add_sources(slist)
+
+        if executor is None:
+            if not self.action:
+                fmt = "Builder %s must have an action to build %s."
+                raise UserError, fmt % (self.get_name(env or self.env),
+                                        map(str,tlist))
+            key = self.action.batch_key(env or self.env, tlist, slist)
+            if key:
+                try:
+                    executor = SCons.Executor.GetBatchExecutor(key)
+                except KeyError:
+                    pass
+                else:
+                    executor.add_batch(tlist, slist)
+
+        if executor is None:
+            executor = SCons.Executor.Executor(self.action, env, [],
+                                               tlist, slist, executor_kw)
+            if key:
+                SCons.Executor.AddBatchExecutor(key, executor)
+
+        # Now set up the relevant information in the target Nodes themselves.
+        for t in tlist:
+            t.cwd = env.fs.getcwd()
+            t.builder_set(self)
+            t.env_set(env)
+            t.add_source(slist)
+            t.set_executor(executor)
+            t.set_explicit(self.is_explicit)
+
+        return SCons.Node.NodeList(tlist)
+
+    def __call__(self, env, target=None, source=None, chdir=_null, **kw):
+        # We now assume that target and source are lists or None.
+        # The caller (typically Environment.BuilderWrapper) is
+        # responsible for converting any scalar values to lists.
+        if chdir is _null:
+            ekw = self.executor_kw
+        else:
+            ekw = self.executor_kw.copy()
+            ekw['chdir'] = chdir
+        if kw:
+            if kw.has_key('srcdir'):
+                def prependDirIfRelative(f, srcdir=kw['srcdir']):
+                    import os.path
+                    if SCons.Util.is_String(f) and not os.path.isabs(f):
+                        f = os.path.join(srcdir, f)
+                    return f
+                if not SCons.Util.is_List(source):
+                    source = [source]
+                source = map(prependDirIfRelative, source)
+                del kw['srcdir']
+            if self.overrides:
+                env_kw = self.overrides.copy()
+                env_kw.update(kw)
+            else:
+                env_kw = kw
+        else:
+            env_kw = self.overrides
+        env = env.Override(env_kw)
+        return self._execute(env, target, source, OverrideWarner(kw), ekw)
 
     def adjust_suffix(self, suff):
-        if suff and not suff[0] in [ '.', '$' ]:
+        if suff and not suff[0] in [ '.', '_', '$' ]:
             return '.' + suff
         return suff
 
-    def get_prefix(self, env):
+    def get_prefix(self, env, sources=[]):
         prefix = self.prefix
         if callable(prefix):
-            prefix = prefix(env)
+            prefix = prefix(env, sources)
         return env.subst(prefix)
 
-    def get_suffix(self, env):
+    def set_suffix(self, suffix):
+        if not callable(suffix):
+            suffix = self.adjust_suffix(suffix)
+        self.suffix = suffix
+
+    def get_suffix(self, env, sources=[]):
         suffix = self.suffix
         if callable(suffix):
-            suffix = suffix(env)
-        else:
-            suffix = self.adjust_suffix(suffix)
+            suffix = suffix(env, sources)
         return env.subst(suffix)
 
-    def src_suffixes(self, env):
-        return map(lambda x, s=self, e=env: e.subst(s.adjust_suffix(x)),
-                   self.src_suffix)
-
     def set_src_suffix(self, src_suffix):
         if not src_suffix:
             src_suffix = []
         elif not SCons.Util.is_List(src_suffix):
             src_suffix = [ src_suffix ]
-        self.src_suffix = src_suffix
+        adjust = lambda suf, s=self: \
+                        callable(suf) and suf or s.adjust_suffix(suf)
+        self.src_suffix = map(adjust, src_suffix)
 
     def get_src_suffix(self, env):
         """Get the first src_suffix in the list of src_suffixes."""
@@ -444,13 +669,6 @@ class BuilderBase:
             return ''
         return ret[0]
 
-    def targets(self, node):
-        """Return the list of targets for this builder instance.
-
-        For most normal builders, this is just the supplied node.
-        """
-        return [ node ]
-
     def add_emitter(self, suffix, emitter):
         """Add a suffix-emitter mapping to this Builder.
 
@@ -461,136 +679,169 @@ class BuilderBase:
         """
         self.emitter[suffix] = emitter
 
-class ListBuilder(SCons.Util.Proxy):
-    """A Proxy to support building an array of targets (for example,
-    foo.o and foo.h from foo.y) from a single Action execution.
-    """
-
-    def __init__(self, builder, env, tlist):
-        SCons.Util.Proxy.__init__(self, builder)
-        self.builder = builder
-        self.scanner = builder.scanner
-        self.env = env
-        self.tlist = tlist
-        self.multi = builder.multi
-
-    def targets(self, node):
-        """Return the list of targets for this builder instance.
+    def add_src_builder(self, builder):
         """
-        return self.tlist
-
-    def __cmp__(self, other):
-        return cmp(self.__dict__, other.__dict__)
-
-    def get_name(self, env):
-        """Attempts to get the name of the Builder."""
+        Add a new Builder to the list of src_builders.
 
-        return "ListBuilder(%s)" % self.builder.get_name(env)
-
-class MultiStepBuilder(BuilderBase):
-    """This is a builder subclass that can build targets in
-    multiple steps.  The src_builder parameter to the constructor
-    accepts a builder that is called to build sources supplied to
-    this builder.  The targets of that first build then become
-    the sources of this builder.
-
-    If this builder has a src_suffix supplied, then the src_builder
-    builder is NOT invoked if the suffix of a source file matches
-    src_suffix.
-    """
-    def __init__(self,  src_builder,
-                        action = None,
-                        prefix = '',
-                        suffix = '',
-                        src_suffix = '',
-                        node_factory = SCons.Node.FS.default_fs.File,
-                        target_factory = None,
-                        source_factory = None,
-                        scanner=None,
-                        emitter=None):
-        BuilderBase.__init__(self, action, prefix, suffix, src_suffix,
-                             node_factory, target_factory, source_factory,
-                             scanner, emitter)
-        if not SCons.Util.is_List(src_builder):
-            src_builder = [ src_builder ]
-        self.src_builder = src_builder
-        self.sdict = {}
-        self.cached_src_suffixes = {} # source suffixes keyed on id(env)
-
-    def __call__(self, env, target = None, source = _null, **kw):
-        if source is _null:
-            source = target
-            target = None
+        This requires wiping out cached values so that the computed
+        lists of source suffixes get re-calculated.
+        """
+        self._memo = {}
+        self.src_builder.append(builder)
 
-        slist = SCons.Node.arg2nodes(source, self.source_factory)
-        final_sources = []
+    def _get_sdict(self, env):
+        """
+        Returns a dictionary mapping all of the source suffixes of all
+        src_builders of this Builder to the underlying Builder that
+        should be called first.
+
+        This dictionary is used for each target specified, so we save a
+        lot of extra computation by memoizing it for each construction
+        environment.
+
+        Note that this is re-computed each time, not cached, because there
+        might be changes to one of our source Builders (or one of their
+        source Builders, and so on, and so on...) that we can't "see."
+
+        The underlying methods we call cache their computed values,
+        though, so we hope repeatedly aggregating them into a dictionary
+        like this won't be too big a hit.  We may need to look for a
+        better way to do this if performance data show this has turned
+        into a significant bottleneck.
+        """
+        sdict = {}
+        for bld in self.get_src_builders(env):
+            for suf in bld.src_suffixes(env):
+                sdict[suf] = bld
+        return sdict
 
-        try:
-            sdict = self.sdict[id(env)]
-        except KeyError:
-            sdict = {}
-            self.sdict[id(env)] = sdict
-            for bld in self.src_builder:
-                if SCons.Util.is_String(bld):
-                    try:
-                        bld = env['BUILDERS'][bld]
-                    except KeyError:
-                        continue
-                for suf in bld.src_suffixes(env):
-                    sdict[suf] = bld
+    def src_builder_sources(self, env, source, overwarn={}):
+        sdict = self._get_sdict(env)
 
         src_suffixes = self.src_suffixes(env)
 
-        for snode in slist:
-            path, ext = self.splitext(snode.get_abspath())
-            if sdict.has_key(ext):
-                src_bld = sdict[ext]
-                tgt = apply(src_bld, (env, path, snode), kw)
-                # Only supply the builder with sources it is capable
-                # of building.
-                if SCons.Util.is_List(tgt):
-                    tgt = filter(lambda x, self=self, suf=src_suffixes:
-                                 self.splitext(SCons.Util.to_String(x))[1] in suf,
-                                 tgt)
-                if not SCons.Util.is_List(tgt):
-                    final_sources.append(tgt)
+        lengths = list(set(map(len, src_suffixes)))
+
+        def match_src_suffix(name, src_suffixes=src_suffixes, lengths=lengths):
+            node_suffixes = map(lambda l, n=name: n[-l:], lengths)
+            for suf in src_suffixes:
+                if suf in node_suffixes:
+                    return suf
+            return None
+
+        result = []
+        for s in SCons.Util.flatten(source):
+            if SCons.Util.is_String(s):
+                match_suffix = match_src_suffix(env.subst(s))
+                if not match_suffix and not '.' in s:
+                    src_suf = self.get_src_suffix(env)
+                    s = self._adjustixes(s, None, src_suf)[0]
+            else:
+                match_suffix = match_src_suffix(s.name)
+            if match_suffix:
+                try:
+                    bld = sdict[match_suffix]
+                except KeyError:
+                    result.append(s)
                 else:
-                    final_sources.extend(tgt)
+                    tlist = bld._execute(env, None, [s], overwarn)
+                    # If the subsidiary Builder returned more than one
+                    # target, then filter out any sources that this
+                    # Builder isn't capable of building.
+                    if len(tlist) > 1:
+                        mss = lambda t, m=match_src_suffix: m(t.name)
+                        tlist = filter(mss, tlist)
+                    result.extend(tlist)
             else:
-                final_sources.append(snode)
+                result.append(s)
+
+        source_factory = env.get_factory(self.source_factory)
 
-        return apply(BuilderBase.__call__,
-                     (self, env, target, final_sources), kw)
+        return env.arg2nodes(result, source_factory)
+
+    def _get_src_builders_key(self, env):
+        return id(env)
+
+    memoizer_counters.append(SCons.Memoize.CountDict('get_src_builders', _get_src_builders_key))
 
     def get_src_builders(self, env):
-        """Return all the src_builders for this Builder.
+        """
+        Returns the list of source Builders for this Builder.
 
-        This is essentially a recursive descent of the src_builder "tree."
+        This exists mainly to look up Builders referenced as
+        strings in the 'BUILDER' variable of the construction
+        environment and cache the result.
         """
-        ret = []
+        memo_key = id(env)
+        try:
+            memo_dict = self._memo['get_src_builders']
+        except KeyError:
+            memo_dict = {}
+            self._memo['get_src_builders'] = memo_dict
+        else:
+            try:
+                return memo_dict[memo_key]
+            except KeyError:
+                pass
+
+        builders = []
         for bld in self.src_builder:
             if SCons.Util.is_String(bld):
-                # All Environments should have a BUILDERS
-                # variable, so no need to check for it.
                 try:
                     bld = env['BUILDERS'][bld]
                 except KeyError:
                     continue
-            ret.append(bld)
-        return ret
+            builders.append(bld)
 
-    def src_suffixes(self, env):
-        """Return a list of the src_suffix attributes for all
-        src_builders of this Builder.
+        memo_dict[memo_key] = builders
+        return builders
+
+    def _subst_src_suffixes_key(self, env):
+        return id(env)
+
+    memoizer_counters.append(SCons.Memoize.CountDict('subst_src_suffixes', _subst_src_suffixes_key))
+
+    def subst_src_suffixes(self, env):
+        """
+        The suffix list may contain construction variable expansions,
+        so we have to evaluate the individual strings.  To avoid doing
+        this over and over, we memoize the results for each construction
+        environment.
         """
+        memo_key = id(env)
         try:
-            return self.cached_src_suffixes[id(env)]
+            memo_dict = self._memo['subst_src_suffixes']
         except KeyError:
-            suffixes = BuilderBase.src_suffixes(self, env)
-            for builder in self.get_src_builders(env):
-                suffixes.extend(builder.src_suffixes(env))
-            self.cached_src_suffixes[id(env)] = suffixes
-            return suffixes
+            memo_dict = {}
+            self._memo['subst_src_suffixes'] = memo_dict
+        else:
+            try:
+                return memo_dict[memo_key]
+            except KeyError:
+                pass
+        suffixes = map(lambda x, s=self, e=env: e.subst(x), self.src_suffix)
+        memo_dict[memo_key] = suffixes
+        return suffixes
+
+    def src_suffixes(self, env):
+        """
+        Returns the list of source suffixes for all src_builders of this
+        Builder.
+
+        This is essentially a recursive descent of the src_builder "tree."
+        (This value isn't cached because there may be changes in a
+        src_builder many levels deep that we can't see.)
+        """
+        sdict = {}
+        suffixes = self.subst_src_suffixes(env)
+        for s in suffixes:
+            sdict[s] = 1
+        for builder in self.get_src_builders(env):
+            for s in builder.src_suffixes(env):
+                if not sdict.has_key(s):
+                    sdict[s] = 1
+                    suffixes.append(s)
+        return suffixes
 
 class CompositeBuilder(SCons.Util.Proxy):
     """A Builder Proxy whose main purpose is to always have
@@ -599,6 +850,7 @@ class CompositeBuilder(SCons.Util.Proxy):
     """
 
     def __init__(self, builder, cmdgen):
+        if __debug__: logInstanceCreation(self, 'Builder.CompositeBuilder')
         SCons.Util.Proxy.__init__(self, builder)
 
         # cmdgen should always be an instance of DictCmdGenerator.
@@ -608,6 +860,9 @@ class CompositeBuilder(SCons.Util.Proxy):
     def add_action(self, suffix, action):
         self.cmdgen.add_action(suffix, action)
         self.set_src_suffix(self.cmdgen.src_suffixes())
-        
-    def __cmp__(self, other):
-        return cmp(self.__dict__, other.__dict__)
+
+# Local Variables:
+# tab-width:4
+# indent-tabs-mode:nil
+# End:
+# vim: set expandtab tabstop=4 shiftwidth=4: