Merge remote-tracking branch 'upstream/master'

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diff --git a/jam-files/boost-build/build/scanner.jam b/jam-files/boost-build/build/scanner.jam
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+# Copyright 2003 Dave Abrahams 
+# Copyright 2002, 2003, 2004, 2005 Vladimir Prus 
+# Distributed under the Boost Software License, Version 1.0. 
+# (See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt) 
+
+#  Implements scanners: objects that compute implicit dependencies for
+#  files, such as includes in C++.
+#
+#  Scanner has a regular expression used to find dependencies, some
+#  data needed to interpret those dependencies (for example, include
+#  paths), and a code which actually established needed relationship
+#  between actual jam targets.
+#
+#  Scanner objects are created by actions, when they try to actualize
+#  virtual targets, passed to 'virtual-target.actualize' method and are
+#  then associated with actual targets. It is possible to use
+#  several scanners for a virtual-target. For example, a single source
+#  might be used by to compile actions, with different include paths.
+#  In this case, two different actual targets will be created, each 
+#  having scanner of its own.
+#
+#  Typically, scanners are created from target type and action's 
+#  properties, using the rule 'get' in this module. Directly creating
+#  scanners is not recommended, because it might create many equvivalent
+#  but different instances, and lead in unneeded duplication of
+#  actual targets. However, actions can also create scanners in a special
+#  way, instead of relying on just target type.
+
+import "class" : new ;
+import property virtual-target property-set ;
+import errors : error ;
+
+#  Base scanner class. 
+class scanner 
+{
+    rule __init__ ( )
+    {
+    }
+    
+    # Returns a pattern to use for scanning
+    rule pattern ( )
+    {
+        error "method must be overriden" ;
+    }
+
+    # Establish necessary relationship between targets,
+    # given actual target beeing scanned, and a list of
+    # pattern matches in that file.
+    rule process ( target : matches * )
+    {
+        error "method must be overriden" ;
+    }        
+}
+
+# Registers a new generator class, specifying a set of 
+# properties relevant to this scanner.  Ctor for that class
+# should have one parameter: list of properties.
+rule register ( scanner-class : relevant-properties * )
+{
+    .registered += $(scanner-class) ;
+    .relevant-properties.$(scanner-class) = $(relevant-properties) ;
+}
+
+# Common scanner class, which can be used when there's only one
+# kind of includes (unlike C, where "" and <> includes have different
+# search paths).
+class common-scanner : scanner 
+{
+    import scanner ;
+    rule __init__ ( includes * )
+    {
+        scanner.__init__ ;
+        self.includes = $(includes) ;
+    }
+            
+    rule process ( target : matches * : binding )
+    {
+        local target_path = [ NORMALIZE_PATH $(binding:D) ] ;
+
+        NOCARE $(matches) ;
+        INCLUDES $(target) : $(matches) ;
+        SEARCH on $(matches) = $(target_path) $(self.includes:G=) ;
+        ISFILE $(matches) ;
+    
+        scanner.propagate $(__name__) : $(matches) : $(target) ;     
+    }
+}
+
+
+# Returns an instance of previously registered scanner,
+# with the specified properties.
+rule get ( scanner-class : property-set ) 
+{
+    if ! $(scanner-class) in $(.registered)
+    {
+        error "attempt to get unregisted scanner" ;
+    }
+    
+    local r = $(.rv-cache.$(property-set)) ;
+    if ! $(r)
+    {
+        r = [ property-set.create 
+            [ property.select $(.relevant-properties.$(scanner-class)) :
+              [ $(property-set).raw ] ] ] ;        
+        .rv-cache.$(property-set) = $(r) ;
+    }
+        
+    if ! $(scanner.$(scanner-class).$(r:J=-))
+    {
+        scanner.$(scanner-class).$(r:J=-) = [ new $(scanner-class) [ $(r).raw ] ] ;
+    }
+    return $(scanner.$(scanner-class).$(r:J=-)) ;    
+}
+
+
+# Installs the specified scanner on actual target 'target'. 
+rule install ( scanner : target 
+    vtarget # virtual target from which 'target' was actualized
+)
+{
+    HDRSCAN on $(target) = [ $(scanner).pattern ] ;
+    SCANNER on $(target) = $(scanner) ;
+    HDRRULE on $(target) = scanner.hdrrule ;
+    
+    # scanner reflects difference in properties affecting    
+    # binding of 'target', which will be known when processing
+    # includes for it, will give information on how to
+    # interpret quoted includes.
+    HDRGRIST on $(target) = $(scanner) ;
+}
+
+# Propagate scanner setting from 'including-target' to 'targets'.
+rule propagate ( scanner : targets * : including-target )
+{
+    HDRSCAN on $(targets) = [ on $(including-target) return $(HDRSCAN) ] ;
+    SCANNER on $(targets) = $(scanner) ;
+    HDRRULE on $(targets) = scanner.hdrrule ;
+    HDRGRIST on $(targets) = [ on $(including-target) return $(HDRGRIST) ] ;
+}
+
+
+rule hdrrule ( target : matches * : binding )
+{
+    local scanner = [ on $(target) return $(SCANNER) ] ;
+    $(scanner).process $(target) : $(matches) : $(binding) ;
+}
+# hdrrule must be available at global scope so that it can be invoked
+# by header scanning
+IMPORT scanner : hdrrule : : scanner.hdrrule ;
+
+
+
+