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128 lines
4.3 KiB
Python
Executable file
128 lines
4.3 KiB
Python
Executable file
#! /usr/bin/env python3
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"""
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combinerefs path
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A helper for analyzing PYTHONDUMPREFS output.
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When the PYTHONDUMPREFS envar is set in a debug build, at Python shutdown
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time Py_FinalizeEx() prints the list of all live objects twice: first it
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prints the repr() of each object while the interpreter is still fully intact.
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After cleaning up everything it can, it prints all remaining live objects
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again, but the second time just prints their addresses, refcounts, and type
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names (because the interpreter has been torn down, calling repr methods at
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this point can get into infinite loops or blow up).
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Save all this output into a file, then run this script passing the path to
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that file. The script finds both output chunks, combines them, then prints
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a line of output for each object still alive at the end:
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address refcnt typename repr
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address is the address of the object, in whatever format the platform C
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produces for a %p format code.
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refcnt is of the form
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"[" ref "]"
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when the object's refcount is the same in both PYTHONDUMPREFS output blocks,
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or
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"[" ref_before "->" ref_after "]"
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if the refcount changed.
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typename is object->ob_type->tp_name, extracted from the second PYTHONDUMPREFS
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output block.
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repr is repr(object), extracted from the first PYTHONDUMPREFS output block.
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CAUTION: If object is a container type, it may not actually contain all the
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objects shown in the repr: the repr was captured from the first output block,
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and some of the containees may have been released since then. For example,
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it's common for the line showing the dict of interned strings to display
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strings that no longer exist at the end of Py_FinalizeEx; this can be recognized
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(albeit painfully) because such containees don't have a line of their own.
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The objects are listed in allocation order, with most-recently allocated
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printed first, and the first object allocated printed last.
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Simple examples:
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00857060 [14] str '__len__'
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The str object '__len__' is alive at shutdown time, and both PYTHONDUMPREFS
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output blocks said there were 14 references to it. This is probably due to
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C modules that intern the string "__len__" and keep a reference to it in a
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file static.
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00857038 [46->5] tuple ()
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46-5 = 41 references to the empty tuple were removed by the cleanup actions
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between the times PYTHONDUMPREFS produced output.
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00858028 [1025->1456] str '<dummy key>'
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The string '<dummy key>', which is used in dictobject.c to overwrite a real
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key that gets deleted, grew several hundred references during cleanup. It
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suggests that stuff did get removed from dicts by cleanup, but that the dicts
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themselves are staying alive for some reason. """
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import re
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import sys
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# Generate lines from fileiter. If whilematch is true, continue reading
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# while the regexp object pat matches line. If whilematch is false, lines
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# are read so long as pat doesn't match them. In any case, the first line
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# that doesn't match pat (when whilematch is true), or that does match pat
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# (when whilematch is false), is lost, and fileiter will resume at the line
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# following it.
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def read(fileiter, pat, whilematch):
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for line in fileiter:
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if bool(pat.match(line)) == whilematch:
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yield line
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else:
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break
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def combine(fname):
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f = open(fname)
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fi = iter(f)
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for line in read(fi, re.compile(r'^Remaining objects:$'), False):
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pass
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crack = re.compile(r'([a-zA-Z\d]+) \[(\d+)\] (.*)')
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addr2rc = {}
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addr2guts = {}
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before = 0
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for line in read(fi, re.compile(r'^Remaining object addresses:$'), False):
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m = crack.match(line)
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if m:
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addr, addr2rc[addr], addr2guts[addr] = m.groups()
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before += 1
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else:
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print('??? skipped:', line)
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after = 0
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for line in read(fi, crack, True):
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after += 1
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m = crack.match(line)
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assert m
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addr, rc, guts = m.groups() # guts is type name here
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if addr not in addr2rc:
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print('??? new object created while tearing down:', line.rstrip())
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continue
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print(addr, end=' ')
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if rc == addr2rc[addr]:
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print('[%s]' % rc, end=' ')
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else:
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print('[%s->%s]' % (addr2rc[addr], rc), end=' ')
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print(guts, addr2guts[addr])
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f.close()
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print("%d objects before, %d after" % (before, after))
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if __name__ == '__main__':
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combine(sys.argv[1])
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