? remove_requirement.diff
Index: project.jam
===================================================================
RCS file: /cvsroot/boost/boost/tools/build/v2/build/project.jam,v
retrieving revision 1.123
diff -u -r1.123 project.jam
--- project.jam	15 Aug 2006 18:48:28 -0000	1.123
+++ project.jam	18 Sep 2006 08:48:16 -0000
@@ -568,16 +568,9 @@
         }
         else if $(attribute) = "requirements" 
         {
-            local result = [ property-set.create-from-user-input
-                $(specification) : $(self.project-module) $(self.location) ] ;
-            
-            # If we have inherited properties, need to refine them with the
-            # specified.
-            local current = $(self.requirements) ;                                    
-            if $(current)
-            {
-                result = [ $(current).refine $(result) ] ;
-            }
+            local result = [ property-set.refine-from-user-input
+                $(self.requirements) : $(specification)
+                  : $(self.project-module) : $(self.location) ] ;
 
             if $(result[1]) = "@error"
             {
Index: property-set.jam
===================================================================
RCS file: /cvsroot/boost/boost/tools/build/v2/build/property-set.jam,v
retrieving revision 1.24
diff -u -r1.24 property-set.jam
--- property-set.jam	26 Jan 2006 13:37:33 -0000	1.24
+++ property-set.jam	18 Sep 2006 08:48:16 -0000
@@ -7,6 +7,7 @@
 import feature ;
 import property ;
 import sequence ;
+import set ;
 
 # Class for storing a set of properties.
 # - there's 1<->1 correspondence between identity and value. No
@@ -386,6 +387,58 @@
     return $(result) ;
 }
 
+# Refines requirements with requirements provided by the user.
+# Specially handles "-<property>value" syntax in specification
+# to remove given requirements.
+# - parent-requirements -- property-set object with requirements
+#   to refine
+# - specification -- string list of requirements provided by the use
+# - project-module -- the module to which context indirect features
+#   will be bound.
+# - location -- the path to which path features are relative.
+#
+#
+rule refine-from-user-input ( parent-requirements : specification * 
+    : project-module : location )
+{
+    if ! $(specification)
+    {
+        return $(parent-requirements) ;
+    }
+    else
+    {
+        local add-requirements ;
+        local remove-requirements ;
+        
+        for local r in $(specification)
+        {
+            local m = [ MATCH "^-(.*)" : $(r) ] ;
+            if $(m)
+            {
+                remove-requirements += $(m) ;
+            }
+            else
+            {
+                add-requirements += $(r) ;
+            }
+        }
+        
+        if $(remove-requirements)
+        {
+            parent-requirements = [ property-set.create 
+                [ set.difference [ $(parent-requirements).raw ] 
+                  : $(remove-requirements) ] ] ;
+            specification = $(add-requirements) ;
+        }
+
+        local requirements = [ property-set.create-from-user-input 
+            $(specification) : $(project-module) $(location) ] ;
+        
+        requirements = [ $(parent-requirements).refine $(requirements) ] ;    
+        return $(requirements) ;
+    }
+}
+
 
 
 # Returns property-set with empty set of properties.
Index: targets.jam
===================================================================
RCS file: /cvsroot/boost/boost/tools/build/v2/build/targets.jam,v
retrieving revision 1.200
diff -u -r1.200 targets.jam
--- targets.jam	17 Sep 2006 17:17:10 -0000	1.200
+++ targets.jam	18 Sep 2006 08:48:16 -0000
@@ -1400,13 +1400,10 @@
   : project       # Project where the main target is to be declared
       )
 {
-    local loc = [ $(project).get location ] ;
-    local jamfile-module = [ $(project).project-module ] ;
-    local requirements = [ property-set.create-from-user-input $(specification)
-      : $(jamfile-module) $(loc) ] ;
+    local requirements = [ property-set.refine-from-user-input 
+        [ $(project).get requirements ] : $(specification) :
+        [ $(project).project-module ] : [ $(project).get location ] ] ;
     
-    local project-requirements = [ $(project).get requirements ] ;
-    requirements = [ $(project-requirements).refine $(requirements) ] ;    
     if $(requirements[1]) = "@error" 
     {
         errors.error "Conflicting requirements for target:" $(requirements) ;