gdb/testsuite/gdb.python/py-inferior-leak.py

   1 # Copyright (C) 2021-2023 Free Software Foundation, Inc.
   2
   3 # This program is free software; you can redistribute it and/or modify
   4 # it under the terms of the GNU General Public License as published by
   5 # the Free Software Foundation; either version 3 of the License, or
   6 # (at your option) any later version.
   7 #
   8 # This program is distributed in the hope that it will be useful,
   9 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 # GNU General Public License for more details.
  12 #
  13 # You should have received a copy of the GNU General Public License
  14 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  15
  16 import tracemalloc
  17 import gdb
  18 import re
  19
  20 # A global variable in which we store a reference to the gdb.Inferior
  21 # object sent to us in the new_inferior event.
  22 inf = None
  23
  24 # Register the new_inferior event handler.
  25 def new_inferior_handler(event):
  26     global inf
  27     inf = event.inferior
  28
  29
  30 gdb.events.new_inferior.connect(new_inferior_handler)
  31
  32 # A global filters list, we only care about memory allocations
  33 # originating from this script.
  34 filters = [tracemalloc.Filter(True, "*py-inferior-leak.py")]
  35
  36 # Add a new inferior, and return the number of the new inferior.
  37 def add_inferior():
  38     output = gdb.execute("add-inferior", False, True)
  39     m = re.search(r"Added inferior (\d+)", output)
  40     if m:
  41         num = int(m.group(1))
  42     else:
  43         raise RuntimeError("no match")
  44     return num
  45
  46
  47 # Run the test.  When CLEAR is True we clear the global INF variable
  48 # before comparing the before and after memory allocation traces.
  49 # When CLEAR is False we leave INF set to reference the gdb.Inferior
  50 # object, thus preventing the gdb.Inferior from being deallocated.
  51 def test(clear):
  52     global filters, inf
  53
  54     # Start tracing, and take a snapshot of the current allocations.
  55     tracemalloc.start()
  56     snapshot1 = tracemalloc.take_snapshot()
  57
  58     # Create an inferior, this triggers the new_inferior event, which
  59     # in turn holds a reference to the new gdb.Inferior object in the
  60     # global INF variable.
  61     num = add_inferior()
  62     gdb.execute("remove-inferiors %s" % num)
  63
  64     # Possibly clear the global INF variable.
  65     if clear:
  66         inf = None
  67
  68     # Now grab a second snapshot of memory allocations, and stop
  69     # tracing memory allocations.
  70     snapshot2 = tracemalloc.take_snapshot()
  71     tracemalloc.stop()
  72
  73     # Filter the snapshots; we only care about allocations originating
  74     # from this file.
  75     snapshot1 = snapshot1.filter_traces(filters)
  76     snapshot2 = snapshot2.filter_traces(filters)
  77
  78     # Compare the snapshots, this leaves only things that were
  79     # allocated, but not deallocated since the first snapshot.
  80     stats = snapshot2.compare_to(snapshot1, "traceback")
  81
  82     # Total up all the deallocated things.
  83     total = 0
  84     for stat in stats:
  85         total += stat.size_diff
  86     return total
  87
  88
  89 # The first time we run this some global state will be allocated which
  90 # shows up as memory that is allocated, but not released.  So, run the
  91 # test once and discard the result.
  92 test(True)
  93
  94 # Now run the test twice, the first time we clear our global reference
  95 # to the gdb.Inferior object, which should allow Python to deallocate
  96 # the object.  The second time we hold onto the global reference,
  97 # preventing Python from performing the deallocation.
  98 bytes_with_clear = test(True)
  99 bytes_without_clear = test(False)
 100
 101 # The bug that used to exist in GDB was that even when we released the
 102 # global reference the gdb.Inferior object would not be deallocated.
 103 if bytes_with_clear > 0:
 104     raise gdb.GdbError("memory leak when gdb.Inferior should be released")
 105 if bytes_without_clear == 0:
 106     raise gdb.GdbError("gdb.Inferior object is no longer allocated")
 107
 108 # Print a PASS message that the test script can see.
 109 print("PASS")