Fix win64 detection.

git-svn-id: http://scons.tigris.org/svn/scons/trunk@4352 fdb21ef1-2011-0410-befe-b5e4ea1792b1

diff --git a/src/engine/SCons/Tool/MSCommon/common.py b/src/engine/SCons/Tool/MSCommon/common.py
index f74d10cb29aa34b2808e06c9e79a4de912e3f895..017892cf766135848b0c06c188e4908dc419929b 100644 (file)
--- a/src/engine/SCons/Tool/MSCommon/common.py
+++ b/src/engine/SCons/Tool/MSCommon/common.py
@@ -54,7 +54,9 @@ else:
 _is_win64 = None
 
 def is_win64():
-    """Return true if running on windows 64 bits."""
+    """Return true if running on windows 64 bits.
+    
+    Works whether python itself runs in 64 bits or 32 bits."""
     # Unfortunately, python does not provide a useful way to determine
     # if the underlying Windows OS is 32-bit or 64-bit.  Worse, whether
     # the Python itself is 32-bit or 64-bit affects what it returns,
@@ -63,17 +65,22 @@ def is_win64():
     # avoid repeated registry calls.
     global _is_win64
     if _is_win64 is None:
-        try:
-            yo = read_reg(r'Software\Wow6432Node')
-        except WindowsError:
-            yo = None
-        _is_win64 = (yo is not None)
+        _is_win64 = has_reg(r"Software\Wow6432Node")
     return _is_win64
 
 
 def read_reg(value):
     return SCons.Util.RegGetValue(SCons.Util.HKEY_LOCAL_MACHINE, value)[0]
 
+def has_reg(value):
+    """Return True if the given key exists in HKEY_LOCAL_MACHINE, False
+    otherwise."""
+    try:
+        SCons.Util.RegOpenKeyEx(SCons.Util.HKEY_LOCAL_MACHINE, value)
+        ret = True
+    except WindowsError:
+        ret = False
+    return ret
 
 # Functions for fetching environment variable settings from batch files.