Added a new internal Boost Build test illustrating a bug in the current Boost Build/Jam implementation and causing targets to be rebuilt when not necessary in some cases.

[SVN r79599]

v2/test/scanner_causing_rebuilds.py

@@ -0,0 +1,84 @@
+#!/usr/bin/python
+
+# Copyright 2012 Jurko Gospodnetic
+# 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)
+
+#   Tests for a bug causing Boost Build's scanner targets to be rebuilt.
+# unnecessarily in the following scenario:
+#  * We want to build target X requiring target A.
+#  * We have a multi-file action generating targets A & B.
+#  * Out action generates target B with a more recent timestamp than target A.
+#  * Target A includes target B.
+#  * Target A has a registered include scanner.
+# Now even if our targets A & B have already been built and are up-to-date
+# (e.g. in a state left by a previous successful build run), our scanner target
+# tasked with scanning target A will be marked for updating, thus causing any
+# targets depending on it to be updated/rebuilt as well.
+
+import BoostBuild
+
+t = BoostBuild.Tester()
+
+t.write("foo.jam", r"""
+import common ;
+import generators ;
+import modules ;
+import type ;
+import types/cpp ;
+
+type.register FOO : foo ;
+type.register BAR : bar ;
+generators.register-standard foo.foo : FOO : CPP BAR ;
+
+local rule sleep-cmd ( delay )
+{
+    if [ modules.peek : NT ]
+    {
+        return ping 127.0.0.1 -n $(delay) -w 1000 >NUL ;
+    }
+    else
+    {
+        return sleep $(delay) ;
+    }
+}
+
+.touch = [ common.file-creation-command ] ;
+.sleep = [ sleep-cmd 2 ] ;
+
+rule foo ( cpp bar : foo : properties * )
+{
+    # We add the INCLUDE relationship between our generated CPP & BAR targets
+    # explicitly instead of relying on Boost Jam's internal implementation
+    # detail - automatically adding such relationships between all files
+    # generated by the same action. This way our test will continue to function
+    # correctly even if the related Boost Jam implementation detail changes.
+    # Note that adding this relationship by adding an #include directive in our
+    # generated CPP file is not good enough as such a relationship would get
+    # added only after the scanner target's relationships have already been
+    # established and they (as affected by our initial INCLUDE relationship) are
+    # the original reason for this test failing.
+    INCLUDES $(cpp) : $(bar) ;
+}
+
+actions foo
+{
+    $(.touch) "$(<[1])"
+    $(.sleep)
+    $(.touch) "$(<[2])"
+}
+""")
+t.write("x.foo", "")
+t.write("jamroot.jam", """\
+import foo ;
+lib x : x.foo : <link>static ;
+""")
+
+
+# Get everything built once.
+t.run_build_system()
+
+# Simply rerunning the build without touching any of its source target files
+# should not cause any files to be affected.
+t.run_build_system()
+t.expect_nothing_more()

v2/test/test_all.py

@@ -243,6 +243,7 @@ tests = ["absolute_sources",
          "remove_requirement",
          "rescan_header",
          "resolution",
+         "scanner_causing_rebuilds",
          "searched_lib",
          "skipping",
          "sort_rule",