Mercurial > hg
view tests/test-1993.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 | 61c0df2b089a |
children | f2719b387380 |
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$ hg init a $ cd a $ echo a > a $ hg ci -Am0 adding a $ echo b > b $ hg ci -Am1 adding b $ hg tag -r0 default warning: tag default conflicts with existing branch name $ hg log changeset: 2:30a83d1e4a1e tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: Added tag default for changeset f7b1eb17ad24 changeset: 1:925d80f479bb user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: 1 changeset: 0:f7b1eb17ad24 tag: default user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: 0 $ hg update 'tag(default)' 0 files updated, 0 files merged, 2 files removed, 0 files unresolved $ hg parents changeset: 0:f7b1eb17ad24 tag: default user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: 0 $ hg update 'branch(default)' 2 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg parents changeset: 2:30a83d1e4a1e tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: Added tag default for changeset f7b1eb17ad24