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Re: [perl #76438] peephole optimiser could prune more dead code

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Ben Morrow
July 13, 2010 10:55
Re: [perl #76438] peephole optimiser could prune more dead code
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Quoth (Nicholas Clark):
> On Tue, Jul 13, 2010 at 01:11:11PM +0000, �var Arnfj�r� Bjarmason wrote:
> > Of course we can't liberally change things that are documented to be
> > undefined as liberally as a C compiler would, becuase there's only one
> > perl(1) but multiple cc(1)'s.
> But whatever we call it, that's the key problem. There is only one
> implementation, and as that implementation strives hard to internally avoid
> C undefined behaviour, its output will be deterministic, in some fashion.
> Hence people come to rely on the current behaviour of the implementation,
> documented or not.

Quite. And 

    print $i++, $i++;

has DWIM forever (probably since perl 1). I'm not saying we *cannot*
change it, just that any change needs to be either only within the scope
of a lexical pragma or to go through a full deprecation cycle with
mandatory warnings before it changes.


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