bpo-18174: regrtest -R 3:3 now also detects FD leak (#7409)

"python -m test --huntrleaks ..." now also checks for leak of file
descriptors.
Co-Authored-By: Richard Oudkerk <shibturn@gmail.com>

Lib/test/regrtest.py

@@ -1416,37 +1416,59 @@ def dash_R(the_module, test, indirect_test, huntrleaks):
     nwarmup, ntracked, fname = huntrleaks
     fname = os.path.join(support.SAVEDCWD, fname)
     repcount = nwarmup + ntracked
+    rc_deltas = [0] * ntracked
+    fd_deltas = [0] * ntracked
+
     print >> sys.stderr, "beginning", repcount, "repetitions"
     print >> sys.stderr, ("1234567890"*(repcount//10 + 1))[:repcount]
     dash_R_cleanup(fs, ps, pic, zdc, abcs)
+    # initialize variables to make pyflakes quiet
+    rc_before = fd_before = 0
     for i in range(repcount):
-        rc_before = sys.gettotalrefcount()
         run_the_test()
         sys.stderr.write('.')
         dash_R_cleanup(fs, ps, pic, zdc, abcs)
         rc_after = sys.gettotalrefcount()
+        fd_after = support.fd_count()
         if i >= nwarmup:
-            deltas.append(rc_after - rc_before)
+            rc_deltas[i - nwarmup] = rc_after - rc_before
+            fd_deltas[i - nwarmup] = fd_after - fd_before
+        rc_before = rc_after
+        fd_before = fd_after
     print >> sys.stderr
 
-    # bpo-30776: Try to ignore false positives:
-    #
-    #   [3, 0, 0]
-    #   [0, 1, 0]
-    #   [8, -8, 1]
-    #
-    # Expected leaks:
-    #
-    #   [5, 5, 6]
-    #   [10, 1, 1]
-    if all(delta >= 1 for delta in deltas):
-        msg = '%s leaked %s references, sum=%s' % (test, deltas, sum(deltas))
-        print >> sys.stderr, msg
-        with open(fname, "a") as refrep:
-            print >> refrep, msg
-            refrep.flush()
-        return True
-    return False
+    # These checkers return False on success, True on failure
+    def check_rc_deltas(deltas):
+        # Checker for reference counters and memomry blocks.
+        #
+        # bpo-30776: Try to ignore false positives:
+        #
+        #   [3, 0, 0]
+        #   [0, 1, 0]
+        #   [8, -8, 1]
+        #
+        # Expected leaks:
+        #
+        #   [5, 5, 6]
+        #   [10, 1, 1]
+        return all(delta >= 1 for delta in deltas)
+
+    def check_fd_deltas(deltas):
+        return any(deltas)
+
+    failed = False
+    for deltas, item_name, checker in [
+        (rc_deltas, 'references', check_rc_deltas),
+        (fd_deltas, 'file descriptors', check_fd_deltas)
+    ]:
+        if checker(deltas):
+            msg = '%s leaked %s %s, sum=%s' % (test, deltas, item_name, sum(deltas))
+            print >> sys.stderr, msg
+            with open(fname, "a") as refrep:
+                print >> refrep, msg
+                refrep.flush()
+            failed = True
+    return failed
 
 def dash_R_cleanup(fs, ps, pic, zdc, abcs):
     import gc, copy_reg

Lib/test/support/__init__.py

@@ -2062,6 +2062,63 @@ def _crash_python():
         _testcapi._read_null()
 
 
+def fd_count():
+    """Count the number of open file descriptors.
+    """
+    if sys.platform.startswith(('linux', 'freebsd')):
+        try:
+            names = os.listdir("/proc/self/fd")
+            return len(names)
+        except FileNotFoundError:
+            pass
+
+    old_modes = None
+    if sys.platform == 'win32':
+        # bpo-25306, bpo-31009: Call CrtSetReportMode() to not kill the process
+        # on invalid file descriptor if Python is compiled in debug mode
+        try:
+            import msvcrt
+            msvcrt.CrtSetReportMode
+        except (AttributeError, ImportError):
+            # no msvcrt or a release build
+            pass
+        else:
+            old_modes = {}
+            for report_type in (msvcrt.CRT_WARN,
+                                msvcrt.CRT_ERROR,
+                                msvcrt.CRT_ASSERT):
+                old_modes[report_type] = msvcrt.CrtSetReportMode(report_type, 0)
+
+    MAXFD = 256
+    if hasattr(os, 'sysconf'):
+        try:
+            MAXFD = os.sysconf("SC_OPEN_MAX")
+        except OSError:
+            pass
+
+    try:
+        count = 0
+        for fd in range(MAXFD):
+            try:
+                # Prefer dup() over fstat(). fstat() can require input/output
+                # whereas dup() doesn't.
+                fd2 = os.dup(fd)
+            except OSError as e:
+                if e.errno != errno.EBADF:
+                    raise
+            else:
+                os.close(fd2)
+                count += 1
+    finally:
+        if old_modes is not None:
+            for report_type in (msvcrt.CRT_WARN,
+                                msvcrt.CRT_ERROR,
+                                msvcrt.CRT_ASSERT):
+                msvcrt.CrtSetReportMode(report_type, old_modes[report_type])
+
+    return count
+
+
 class SaveSignals:
     """
     Save an restore signal handlers.

Lib/test/test_regrtest.py

@@ -511,6 +511,24 @@ class ArgsTestCase(BaseTestCase):
         """)
         self.check_leak(code, 'references')
 
+    @unittest.skipUnless(Py_DEBUG, 'need a debug build')
+    def test_huntrleaks_fd_leak(self):
+        # test --huntrleaks for file descriptor leak
+        code = textwrap.dedent("""
+            import os
+            import unittest
+            from test import support
+
+            class FDLeakTest(unittest.TestCase):
+                def test_leak(self):
+                    fd = os.open(__file__, os.O_RDONLY)
+                    # bug: never close the file descriptor
+
+            def test_main():
+                support.run_unittest(FDLeakTest)
+        """)
+        self.check_leak(code, 'file descriptors')
+
     def test_list_tests(self):
         # test --list-tests
         tests = [self.create_test() for i in range(5)]