Mercurial > hg
view tests/test-commit-copy.t @ 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 | b90199179eb5 |
children | ec5886db9dc6 |
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$ hg init dir $ cd dir $ echo bleh > bar $ hg add bar $ hg ci -m 'add bar' $ hg cp bar foo $ echo >> bar $ hg ci -m 'cp bar foo; change bar' $ hg debugrename foo foo renamed from bar:26d3ca0dfd18e44d796b564e38dd173c9668d3a9 $ hg debugindex .hg/store/data/bar.i rev offset length base linkrev nodeid p1 p2 0 0 6 0 0 26d3ca0dfd18 000000000000 000000000000 1 6 7 1 1 d267bddd54f7 26d3ca0dfd18 000000000000