BUG: fix macho detection for tiny files.

macholib assumes any path given to MachO constructor is at least 4
bytes.

Author: cournape

machotools/detect.py

@@ -1,9 +1,16 @@
+import os
+
 from macholib.MachO import MachO
 
 def detect_macho_type(path):
     """
     Returns None if not a mach-o.
+
+    Raise an error for non-existing paths.
     """
+    if os.stat(path).st_size < 4:
+        return None
+
     try:
         p = MachO(path)
     except ValueError as e:
@@ -18,6 +25,9 @@ def detect_macho_type(path):
 
 def is_macho(path):
     """Return True if the given path is a Mach-O binary."""
+    if os.stat(path).st_size < 4:
+        return None
+
     try:
         MachO(path)
         return True

machotools/tests/common.py

@@ -29,6 +29,8 @@
 
 NO_MACHO_FILE = op.join(DYLIB_DIRECTORY, "Makefile")
 
+TINY_FILE = op.join(DYLIB_DIRECTORY, "tiny")
+
 @contextlib.contextmanager
 def mkdtemp():
     d = tempfile.mkdtemp()

machotools/tests/data/tiny

@@ -0,0 +1 @@
+a

machotools/tests/test_detect.py

@@ -2,9 +2,14 @@
 
 from machotools.detect import is_macho, is_dylib, is_executable, is_bundle
 
-from machotools.tests.common import FOO_DYLIB, SIMPLE_MAIN, SIMPLE_BUNDLE, NO_MACHO_FILE
+from machotools.tests.common import (
+    FOO_DYLIB, SIMPLE_MAIN, SIMPLE_BUNDLE, NO_MACHO_FILE, TINY_FILE
+)
 
 class TestDetect(unittest.TestCase):
+    def test_tiny_file(self):
+        self.assertFalse(is_macho(TINY_FILE))
+
     def test_dylib(self):
         self.assertTrue(is_dylib(FOO_DYLIB))
         self.assertFalse(is_bundle(FOO_DYLIB))