Mercurial > hg
view tests/test-diff-hashes.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 | 4c94b6d0fb1c |
children | 117f9190c1ba |
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$ hg init a $ cd a $ hg diff inexistent1 inexistent2 inexistent1: No such file or directory inexistent2: No such file or directory $ echo bar > foo $ hg add foo $ hg ci -m 'add foo' $ echo foobar > foo $ hg ci -m 'change foo' $ hg --quiet diff -r 0 -r 1 --- a/foo Thu Jan 01 00:00:00 1970 +0000 +++ b/foo Thu Jan 01 00:00:00 1970 +0000 @@ -1,1 +1,1 @@ -bar +foobar $ hg diff -r 0 -r 1 diff -r a99fb63adac3 -r 9b8568d3af2f foo --- a/foo Thu Jan 01 00:00:00 1970 +0000 +++ b/foo Thu Jan 01 00:00:00 1970 +0000 @@ -1,1 +1,1 @@ -bar +foobar $ hg --verbose diff -r 0 -r 1 diff -r a99fb63adac3 -r 9b8568d3af2f foo --- a/foo Thu Jan 01 00:00:00 1970 +0000 +++ b/foo Thu Jan 01 00:00:00 1970 +0000 @@ -1,1 +1,1 @@ -bar +foobar $ hg --debug diff -r 0 -r 1 diff -r a99fb63adac3f31816a22f665bc3b7a7655b30f4 -r 9b8568d3af2f1749445eef03aede868a6f39f210 foo --- a/foo Thu Jan 01 00:00:00 1970 +0000 +++ b/foo Thu Jan 01 00:00:00 1970 +0000 @@ -1,1 +1,1 @@ -bar +foobar