In restart check whether file is executable

Author: rocky

test/unit/lib/test_lib_file.py

@@ -6,29 +6,59 @@
 
 import pytest
 
-from trepan.lib import file as Mfile
+from trepan.lib.file import executable, lookupmodule, readable
 
 
 def test_lookupmodule():
-    m, f = Mfile.lookupmodule("os.path")
+    m, f = lookupmodule("os.path")
     assert f
     assert m
-    m, f = Mfile.lookupmodule(__file__)
+    m, f = lookupmodule(__file__)
     assert f
     assert m is None
-    assert (None, None) == Mfile.lookupmodule("fafdsafdsa")
+    assert (None, None) == lookupmodule("fafdsafdsa")
     return
 
 
-pytest.mark.skipif(sys.platform == "win32", reason="Does not work on MS Windows")
+@pytest.mark.skipif(sys.platform == "win32", reason="Does not work on MS Windows")
+def test_readable():
+    assert not readable("fdafdsa")
+    i = 1
+    for mode, can_read in [
+        (stat.S_IRUSR, True),  # 1
+        (stat.S_IWUSR, False),  # 2
+        (stat.S_IRGRP, True),  # 3
+        (stat.S_IWGRP, False),  # 4
+        (stat.S_IROTH, True),  # 5
+        (stat.S_IWOTH, False),  # 6
+    ]:
+        f = tempfile.NamedTemporaryFile()
+        os.chmod(f.name, mode)
+        assert can_read == readable(f.name), f"Test {i} file mode {oct(mode)}"
+        f.close()
+        i += 1
+        pass
+    return
 
 
-def test_readable():
-    assert not Mfile.readable("fdafdsa")
-    for mode, can_read in [(stat.S_IRUSR, True), (stat.S_IWUSR, False)]:
+@pytest.mark.skipif(sys.platform == "win32", reason="Does not work on MS Windows")
+def test_executable():
+    i = 1
+    for mode, can_read in [
+        (stat.S_IRUSR | stat.S_IXUSR, True),  # 1
+        (stat.S_IRUSR, False),  # 2
+        (stat.S_IWGRP | stat.S_IXGRP, False),  # 3
+        (stat.S_IWGRP, False),  # 4
+        (stat.S_IRGRP | stat.S_IXGRP, True),  # 5
+        (stat.S_IRGRP, False),  # 6
+        (stat.S_IWGRP, False),  # 7
+        (stat.S_IROTH | stat.S_IXOTH, True),  # 8
+    ]:
         f = tempfile.NamedTemporaryFile()
         os.chmod(f.name, mode)
-        assert can_read == Mfile.readable(f.name)
+
+        assert can_read == executable(f.name), f"Test {i} file mode {oct(mode)}"
         f.close()
+        i += 1
         pass
     return

trepan/lib/file.py

@@ -18,6 +18,7 @@
 import os
 import stat
 import sys
+from typing import Optional
 
 import pyficache
 
@@ -26,7 +27,7 @@ def file_list():
     return list(set(pyficache.cached_files() + list(pyficache.file2file_remap.keys())))
 
 
-def is_compiled_py(filename):
+def is_compiled_py(filename) -> bool:
     """
     Given a file name, return True if the suffix is pyo or pyc (an
     optimized bytecode file).
@@ -35,9 +36,25 @@ def is_compiled_py(filename):
 
 
 READABLE_MASK = stat.S_IRUSR | stat.S_IRGRP | stat.S_IROTH
+EXECUTABLE_MASK = stat.S_IXOTH | stat.S_IXGRP | stat.S_IXUSR
 
 
-def readable(path):
+def executable(path: str) -> Optional[bool]:
+    """Test whether a path exists and is readable.  Returns None for
+    broken symbolic links or a failing stat() and False if
+    the file exists but does not have read permission. True is returned
+    if the file is readable."""
+    try:
+        st = os.stat(path)
+        if 0 == st.st_mode & READABLE_MASK:
+            return False
+        return 0 != st.st_mode & EXECUTABLE_MASK
+    except os.error:
+        return None
+    return True
+
+
+def readable(path: str) -> Optional[bool]:
     """Test whether a path exists and is readable.  Returns None for
     broken symbolic links or a failing stat() and False if
     the file exists but does not have read permission. True is returned

trepan/processor/command/restart.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
-#  Copyright (C) 2009, 2013, 2015, 2020, 2023 Rocky Bernstein
+#  Copyright (C) 2009, 2013, 2015, 2020, 2023-2024
+#  Rocky Bernstein
 #
 #  This program is free software: you can redistribute it and/or modify
 #  it under the terms of the GNU General Public License as published by
@@ -16,6 +17,7 @@
 import atexit
 import os
 
+from trepan.lib.file import executable
 from trepan.misc import wrapped_lines
 
 # Our local modules
@@ -37,11 +39,17 @@ class RestartCommand(DebuggerCommand):
 
     short_help = "(Hard) restart of program via execv()"
 
+    # FIXME: add mechanism for adding python interpreter.
     DebuggerCommand.setup(locals(), category="support", max_args=0)
 
     def run(self, args):
         sys_argv = self.debugger.restart_argv()
         if sys_argv and len(sys_argv) > 0:
+            program_file = sys_argv[0]
+            if not executable(sys_argv[0]):
+                self.errmsg(f'File "{program_file}" is not marked executable.')
+                return
+
             confirmed = self.confirm("Restart (execv)", False)
             if confirmed:
                 self.msg(
@@ -55,7 +63,7 @@ def run(self, args):
                     atexit._run_exitfuncs()
                 except Exception:
                     pass
-                os.execvp(sys_argv[0], sys_argv)
+                os.execvp(program_file, sys_argv)
                 pass
             pass
         else: