diff options
author | Michael Stahl <mstahl@redhat.com> | 2014-10-20 15:33:05 +0200 |
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committer | Michael Stahl <mstahl@redhat.com> | 2014-10-20 17:14:37 +0200 |
commit | a4e219eee6314f26b7d9058e714c62facc2bc08c (patch) | |
tree | 8d72e162c0be8946ea299d9e2990994522895ca0 /bin | |
parent | 7ce03365e8e655c4c9636d1acbc02c530114b2ce (diff) |
add bin/refcount_leak.py script to help detect leaks of UNO objects
Initially this didn't help at all, but with some tweaks it now finds
the leaked ChartModel as the #3 and #4 printed stacks, with a very bad
score of 40.
Change-Id: I918bcb64bad0b9432bf2b670b03915836fb34a11
Diffstat (limited to 'bin')
-rwxr-xr-x | bin/refcount_leak.py | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/bin/refcount_leak.py b/bin/refcount_leak.py new file mode 100755 index 000000000000..2a24cb51e80f --- /dev/null +++ b/bin/refcount_leak.py @@ -0,0 +1,179 @@ +#!/usr/bin/python3 +# -*- tab-width: 4; indent-tabs-mode: nil; py-indent-offset: 4 -*- +# +# This file is part of the LibreOffice project. +# +# This Source Code Form is subject to the terms of the Mozilla Public +# License, v. 2.0. If a copy of the MPL was not distributed with this +# file, You can obtain one at http://mozilla.org/MPL/2.0/. +# + +### script to help debug leaks of reference counted objects + +## I. to use it, first override acquire() and release() + +# Foo * g_pTrackedFoo = 0; + +# Foo::Foo() +# static int nFoos = 0; +# if (++nFoos == 42) // track instance #42 +# g_pTrackedFoo = this; + +# void Foo::acquire() +# if (this == g_pTrackedFoo) +# ; // set gdb breakpoint here +# Foo_Base::acquire() + +# void Foo::release() +# if (this == g_pTrackedFoo) +# ; // set gdb breakpoint here +# Foo_Base::release() + +## II. run test/soffice in gdb and set breakpoints in acquire/release +## with a command to print the backtrace + +# set logging on +# break foo.cxx:123 +# break foo.cxx:234 + +# command 1 2 +# bt +# c +# end +# run + +## III. now feed logfile gdb.txt into this script + +# bin/refcount_leak.py < gdb.txt + +### + +from operator import itemgetter +import re +import sys + +threshold = 2 + +class Trace: + clock = 0 # global counter + # frames: list of stack frames, beginning with outermost + def __init__(self, lines): + lines.reverse() + self.frames = lines + Trace.clock += 1 + self.clock = Trace.clock + +def addTrace(traces, lines): + if not(traces is None) and len(lines) > 0: + traces.append(Trace(lines)) + +def readGdbLog(infile): + traces_acquire = [] + traces_release = [] + current = None + lines = [] + apattern = re.compile("^Breakpoint.*::acquire") + rpattern = re.compile("^Breakpoint.*::release") + for line in infile: + if apattern.match(line): + addTrace(current, lines) + lines = [] + current = traces_acquire + if rpattern.match(line): + addTrace(current, lines) + lines = [] + current = traces_release + if line.startswith("#"): + # strip #123 stack frame number, and newline + lines.append(line[line.index("0x"):-1]) + addTrace(current, lines) + print("# parsed traces acquire: ", len(traces_acquire)) + print("# parsed traces release: ", len(traces_release)) + return (traces_acquire, traces_release) + +def getFunction(frame): + start = frame.index(" in ") + len(" in ") + try: + end = frame.index(" at ", start) + except ValueError as e: + # argh... stack frames may be split across multiple lines if + # a parameter has a fancy pretty printer + return frame[start:] + return frame[start:end] + + +def matchStack(trace_acquire, trace_release): + if trace_release.clock < trace_acquire.clock: + return None # acquire must precede release + common = 0 + refpattern = re.compile(r"::Reference<.*>::Reference\(") + for (frame1, frame2) in zip(trace_release.frames, trace_acquire.frames): + if frame1 == frame2: + common += 1 + else: + if getFunction(frame1) == getFunction(frame2): + common += 1 + acquireframes = len(trace_acquire.frames) + # there is sometimes a dozen frames of UNO type related junk + # on the stack where the acquire() happens, which breaks the + # matching; try to avoid that + for i in range(common, acquireframes): + if refpattern.search(trace_acquire.frames[i]): + acquireframes = i+1 # cut off junk above Reference ctor + break + score = max(len(trace_release.frames), acquireframes) - common + # smaller score is better + return (score, trace_release.clock - trace_acquire.clock) + +# brute force greedy n^2 matching +def matchStacks(traces_acquire, traces_release): + matches = [] + for release in traces_release: + for acquire in traces_acquire: + score = matchStack(acquire, release) + if score is not None: + matches.append((score, acquire, release)) + matches.sort(key=itemgetter(0)) + return matches + +def bestMatches(traces_acquire, traces_release, matches): + traces_aunmatched = traces_acquire + traces_runmatched = traces_release + bestmatches = [] + for (score,acquire,release) in matches: + if not(acquire in traces_aunmatched and release in traces_runmatched): + continue + traces_aunmatched.remove(acquire) + traces_runmatched.remove(release) + bestmatches.append((score,acquire,release)) + print("# unmatched acquire: ", len(traces_aunmatched)) + print("# unmatched release: ", len(traces_runmatched)) + return (bestmatches,traces_aunmatched,traces_runmatched) + +def printTrace(trace): + for frame in reversed(trace.frames): + print(" ", frame) + +def printMatched(bestmatches): + for (score,acquire,release) in reversed(bestmatches): + print("\n*** Matched trace with score: ", score) + print(" acquire: ") + printTrace(acquire) + print(" release: ") + printTrace(release) + +def printUnmatched(traces, prefix): + for trace in traces: + print("\n*** Unmatched trace (", prefix, "):") + printTrace(trace) + +if __name__ == "__main__": + (traces_acquire, traces_release) = readGdbLog(sys.stdin) + matches = matchStacks(traces_acquire, traces_release) + (bestmatches,traces_au,traces_ru) = bestMatches(traces_acquire, traces_release, matches) + # print output, sorted with the most suspicious stuff first: + printUnmatched(traces_au, "acquire") + printUnmatched(traces_ru, "release") + printMatched(bestmatches) + +# vim:set shiftwidth=4 softtabstop=4 expandtab: |