Mercurial > hg
annotate tests/test-revlog-ancestry.py.out @ 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> |
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date | Sun, 24 Apr 2011 19:25:10 -0400 |
parents | c7cc40fd74f6 |
children | eb88ed4269c5 |
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1 Ancestors of 5 |
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2 4 2 0 |
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3 Ancestors of 6 and 5 |
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4 3 4 2 1 0 |
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5 Ancestors of 5 and 4 |
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6 4 2 0 |
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7 |
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8 Descendants of 5 |
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9 7 8 |
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10 Descendants of 5 and 3 |
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11 6 7 8 |
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12 Descendants of 5 and 4 |
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13 5 7 8 |