Filter null values from the _concat() list. (Chad Austin)

3 files changed, 22 insertions, 12 deletions

diff --git a/src/CHANGES.txt b/src/CHANGES.txt
index bf2c760..b5ed500 100644
--- a/src/CHANGES.txt
+++ b/src/CHANGES.txt
@@ -22,6 +22,9 @@ RELEASE 0.96 - XXX
   - Allow the emitter argument to a Builder() to be or expand to a list
     of emitter functions, which will be called in sequence.
 
+  - Suppress null values in construction variables like $LIBS that use
+    the internal _concat() function.
+
   From Chad Austin and Christoph Wiedemann:
 
   - Add support for a $RPATH variable to supply a list of directories
diff --git a/src/engine/SCons/Defaults.py b/src/engine/SCons/Defaults.py
index 94ab8d5..89ac0d3 100644
--- a/src/engine/SCons/Defaults.py
+++ b/src/engine/SCons/Defaults.py
@@ -173,20 +173,21 @@ def _concat(prefix, list, suffix, env, f=lambda x: x):
 
     for x in list:
         x = str(x)
+        if x:
 
-        if prefix:
-            if prefix[-1] == ' ':
-                ret.append(prefix[:-1])
-            elif x[:len(prefix)] != prefix:
-                x = prefix + x
+            if prefix:
+                if prefix[-1] == ' ':
+                    ret.append(prefix[:-1])
+                elif x[:len(prefix)] != prefix:
+                    x = prefix + x
 
-        ret.append(x)
+            ret.append(x)
 
-        if suffix:
-            if suffix[0] == ' ':
-                ret.append(suffix[1:])
-            elif x[-len(suffix):] != suffix:
-                ret[-1] = ret[-1]+suffix
+            if suffix:
+                if suffix[0] == ' ':
+                    ret.append(suffix[1:])
+                elif x[-len(suffix):] != suffix:
+                    ret[-1] = ret[-1]+suffix
 
     return ret
 
diff --git a/test/LIBS.py b/test/LIBS.py
index 645c625..c91e38d 100644
--- a/test/LIBS.py
+++ b/test/LIBS.py
@@ -42,6 +42,7 @@ foo1_exe = test.workpath('foo1' + _exe)
 foo2_exe = test.workpath('foo2' + _exe)
 foo3_exe = test.workpath('foo3' + _exe)
 foo4_exe = test.workpath('foo4' + _exe)
+foo5_exe = test.workpath('foo5' + _exe)
 
 test.write('SConstruct', """
 env = Environment(LIBS=['bar'], LIBPATH = '.')
@@ -52,6 +53,8 @@ env3 = Environment(LIBS='bar', LIBPATH = '.')
 env3.Program(target='foo3', source='foo3.c')
 env4 = Environment(LIBS=File(r'%s'), LIBPATH = '.')
 env4.Program(target='foo4', source='foo4.c')
+env5 = Environment(LIBS=['bar', '$UNSPECIFIED'], LIBPATH = '.')
+env5.Program(target='foo5', source='foo5.c')
 SConscript('sub1/SConscript', 'env')
 SConscript('sub2/SConscript', 'env')
 """ % (bar_lib, bar_lib))
@@ -84,6 +87,7 @@ test.write('foo1.c', foo_contents)
 test.write('foo2.c', foo_contents)
 test.write('foo3.c', foo_contents)
 test.write('foo4.c', foo_contents)
+test.write('foo5.c', foo_contents)
 
 test.write(['sub1', 'bar.c'], r"""
 #include <stdio.h>
@@ -112,12 +116,14 @@ void baz()
 }
 """)
 
-test.run(arguments = '.')
+# ar sometimes produces a "warning" on stderr -- ar: creating sub1/libbar.a
+test.run(arguments = '.', stderr=None)
 
 test.run(program=foo1_exe, stdout='sub1/bar.c\nsub1/baz.c\n')
 test.run(program=foo2_exe, stdout='sub1/bar.c\nsub1/baz.c\n')
 test.run(program=foo3_exe, stdout='sub1/bar.c\nsub1/baz.c\n')
 test.run(program=foo4_exe, stdout='sub1/bar.c\nsub1/baz.c\n')
+test.run(program=foo5_exe, stdout='sub1/bar.c\nsub1/baz.c\n')
 
 #
 test.write('SConstruct', """