Mercurial > hg
view tests/md5sum.py @ 14007:d764463b433e
atomictempfile: avoid infinite recursion in __del__().
The problem is that a programmer using atomictempfile directly can
make an innocent everyday mistake -- not enough args to the
constructor -- which escalates badly. You would expect a simple
TypeError crash in that case, but you actually get an infinite
recursion that is surprisingly difficult to kill: it happens between
__del__() and __getattr__(), and Python does not handle infinite
recursion from __del__() well.
The fix is to not implement __getattr__(), but instead assign instance
attributes for the methods we wish to delegate to the builtin file
type: write() and fileno(). I've audited mercurial.* and hgext.* and
found no users of atomictempfile using methods other than write() and
rename(). I audited third-party extensions and found one (snap)
passing an atomictempfile to util.fstat(), so I also threw in
fileno().
The last time I submitted a similar patch, Matt proposed that we make
atomictempfile a subclass of file instead of wrapping it. Rejected on
grounds of unnecessary complexity: for one thing, it would make the
Windows implementation of posixfile quite a bit more complex. It would
have to become a subclass of file rather than a simple function -- but
since it's written in C, this is non-obvious and non-trivial.
Furthermore, there's nothing wrong with wrapping objects and
delegating methods: it's a well-established pattern that works just
fine in many cases. Subclassing is not the answer to all of life's
problems.
author | Greg Ward <greg@gerg.ca> |
---|---|
date | Sun, 24 Apr 2011 19:25:10 -0400 |
parents | a6477aa893b8 |
children | 1ffeeb91c55d |
line wrap: on
line source
#!/usr/bin/env python # # Based on python's Tools/scripts/md5sum.py # # This software may be used and distributed according to the terms # of the PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2, which is # GPL-compatible. import sys, os try: from hashlib import md5 except ImportError: from md5 import md5 try: import msvcrt msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY) msvcrt.setmode(sys.stderr.fileno(), os.O_BINARY) except ImportError: pass for filename in sys.argv[1:]: try: fp = open(filename, 'rb') except IOError, msg: sys.stderr.write('%s: Can\'t open: %s\n' % (filename, msg)) sys.exit(1) m = md5() try: while 1: data = fp.read(8192) if not data: break m.update(data) except IOError, msg: sys.stderr.write('%s: I/O error: %s\n' % (filename, msg)) sys.exit(1) sys.stdout.write('%s %s\n' % (m.hexdigest(), filename)) sys.exit(0)