--- SConstruct
+++ SConstruct
@@ -36,12 +36,25 @@
 
 ### Options exposed via SCons
 opts = Options('custom.py')
-opts.Add('opt', 'Compiler flags for optimization/debugging', "-g -O3")
+opts.Add('opt', 'Compiler flags for optimization/debugging', "")
 opts.Add('warn', 'Compiler flags for warnings', "-Wall -D__warn_unused_result__=__far__")
 opts.Add('prefix', 'The installation root for iulib', "/usr/local")
 
+env = Environment(options=opts)
+
+import SCons.Util
+if os.environ.has_key('CC'):
+	env['CC'] = os.environ['CC']
+if os.environ.has_key('CFLAGS'):
+	env['CCFLAGS'] += SCons.Util.CLVar(os.environ['CFLAGS'])
+if os.environ.has_key('CXX'):
+	env['CXX'] = os.environ['CXX']
+if os.environ.has_key('CXXFLAGS'):
+	env['CXXFLAGS'] += SCons.Util.CLVar(os.environ['CXXFLAGS'])
+if os.environ.has_key('LDFLAGS'):
+	env['LINKFLAGS'] += SCons.Util.CLVar(os.environ['LDFLAGS'])
+
 ### globals
-env = Environment(options=opts, CXXFLAGS="${opt} ${warn}")
 Help(opts.GenerateHelpText(env))
 conf = Configure(env)
 if "-DUNSAFE" in env["opt"]:
@@ -134,7 +147,7 @@
                   src_suffix = '')
 progs.Append(BUILDERS={'Test':test_builder})
 
-if True: #"test" in COMMAND_LINE_TARGETS:
+if "test" in COMMAND_LINE_TARGETS:
     for file in glob.glob("*/test-*.cc") + glob.glob("*/*/test-*.cc"):
         if not file.startswith('vidio'):
             progs.Program(file[:-3],file)