[Python-Dev] Re: [Python-checkins] python/dist/src/Python compile.c, 2.319, 2.320

[David Abrahams]

Guido van Rossum <guido at python.org> writes:

>> > Hm, shouldn't the bytecode optimizer only be used when -O is used, and
>> > hence pyo files are being written?
>> 
>> Why?  That would throw away most of the benefits to most of the
>> users and gain nothing in return.  The peepholer was in place in for
>> Py2.3 and only benefits were seen.  I would save the -O option for
>> something where there is a trade-off (loss of docstrings, excessive
>> compilation time, possibly risky optimizations, or somesuch).  Here,
>> the peepholer is superfast and costs almost nothing.
>
> Maybe I'm out of tune, but I thought that optimizations should be
> turned off by default because most people don't need them and because
> of the risk that the optimizer might break something.  Haven't there
> been situations in Python where one optimization or another was found
> to be unsafe after having been in use (in a release!) for a long
> time?

Isn't that a good argument for having them turned on all the time?
The easiest way to ship code that suffers from an optimizer bug is to
do all your development and most of your testing with unoptimized
code.

In C/C++, there's a good reason to develop code unoptimized: it's much
easier to debug.  I'm not sure that applies to Python.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com