[Python-Dev] cpython: fix compiler warning by implementing this more cleverly (original) (raw)

Terry Reedy tjreedy at udel.edu
Wed Nov 23 07:49:28 CET 2011

On 11/22/2011 7:42 PM, Benjamin Peterson wrote:

2011/11/22 Antoine Pitrou<solipsis at pitrou.net>:

On Tue, 22 Nov 2011 16:42:35 -0500 Benjamin Peterson<benjamin at python.org> wrote:

2011/11/22 Antoine Pitrou<solipsis at pitrou.net>:

On Tue, 22 Nov 2011 21:29:43 +0100 benjamin.peterson<python-checkins at python.org> wrote:

http://hg.python.org/cpython/rev/77ab830930ae changeset: 73697:77ab830930ae user: Benjamin Peterson<benjamin at python.org> date: Tue Nov 22 15:29:32 2011 -0500 summary: fix compiler warning by implementing this more cleverly

You mean "more obscurely"? Obfuscating the original intent in order to disable a compiler warning doesn't seem very wise to me. Well, I think it makes sense that the kind tells you how many bytes are in it. Yes, but "kind * 2 + 2" looks like a magical formula, while the explicit switch let you check mentally that each estimate was indeed correct. I don't see how it's more magic than hardcoding 4, 6, and 10. Don't you have to mentally check that those are correct?

I personally strongly prefer the one-line formula to the hardcoded magic numbers calculated from the formula. I find it much more readable. To me, the only justification for the switch would be if there is a serious worry about the kind being changed to something other than 1, 2, or 4. But the fact that this is checked with an assert that can be optimized away negates that. The one-liner could be followed by assert(kind==1 || kind==2 || kind==4) which would also serve to remind the reader of the possibilities. You could even follow the formula with /* 4, 6, or 10 */ I think you reverted too soon.

-- Terry Jan Reedy

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