Issue 1681: Fix the ability of add_src_builder() to handle arbitrary

builder objects by eliminating unintentional re-use of a class
list for the src_builder attribute.

2 files changed, 7 insertions, 2 deletions

diff --git a/src/engine/SCons/Builder.py b/src/engine/SCons/Builder.py
index 2e10a8d..45bd99a 100644
--- a/src/engine/SCons/Builder.py
+++ b/src/engine/SCons/Builder.py
@@ -363,7 +363,7 @@ class BuilderBase:
                         name = None,
                         chdir = _null,
                         is_explicit = 1,
-                        src_builder = [],
+                        src_builder = None,
                         ensure_suffix = False,
                         **overrides):
         if __debug__: logInstanceCreation(self, 'Builder.BuilderBase')
@@ -410,7 +410,9 @@ class BuilderBase:
             self.executor_kw['chdir'] = chdir
         self.is_explicit = is_explicit
 
-        if not SCons.Util.is_List(src_builder):
+        if src_builder is None:
+            src_builder = []
+        elif not SCons.Util.is_List(src_builder):
             src_builder = [ src_builder ]
         self.src_builder = src_builder
 
diff --git a/src/engine/SCons/BuilderTests.py b/src/engine/SCons/BuilderTests.py
index 1b7bc38..eeb3b3f 100644
--- a/src/engine/SCons/BuilderTests.py
+++ b/src/engine/SCons/BuilderTests.py
@@ -840,6 +840,9 @@ class BuilderTestCase(unittest.TestCase):
         s = map(str, tgt.sources[0].sources)
         assert s == ['aaa.bar'], s
 
+        builder3 = SCons.Builder.Builder(action='bld3')
+        assert not builder3.src_builder is builder1.src_builder
+
         builder4 = SCons.Builder.Builder(action='bld4',
                                          src_suffix='.i',
                                          suffix='_wrap.c')