Hi Dmitry,
----- Original Message -----
From: "Dmitry Stogov"
Sent: Wednesday, July 30, 2008
> Hi Matt,
>
> does the following code work with your patch?
>
> <?php
> function foo() {
> static $a = A + B;
> var_dump($a);
> }
> const A = 1;
> const B = 2;
> foo();
> ?>
>
> It would be hard to explain why some of constant expression work, but
> others don't.
No, it doesn't. That would of course require additional changes (I don't
know how to do that, didn't even look into it), and was also mentioned with
Nuno's patch. I just included the part I did for something "closer" to what
was talked about last time. The only explanation I know of would be that it
only works with *literals*, not named constants. But yes, it's hard to
understand. :-)
But anyway, it doesn't really matter to me about that, the main point (like
Nuno's) was the the folding of constant expressions in the other areas
(especially negative numbers). And like I said, it's more useful after
constant substitution with function flags being ORed and things like that...
But that could always be applied at a later date/version since it doesn't
break compatibility, right?
> Anyway, it's too late for this patches.
> 5.3 is going to be frozen.
Well, what about the behavior change I mentioned? Something should be done
about that, I'm sure. That's what the second small patch
("signed_expr_tweaks") was for.
Actually, I wrote the above right after getting your message, but didn't
send it then, because I had only been thinking about the parser, and thought
of a more proper fix in zend_compile.c for the behavior difference (and
something else). I will send the fix shortly in a reply to the previous
thread about constant substitution... :-)
> Thanks. Dmitry.
Thanks,
Matt
> Matt Wilmas wrote:
> > Hi Dmitry, all,
> >
> > I was going to send this patch as a companion one to go with the
> > compile-time constant substitution change (Nuno sent a message about
this
> > [1] last Sep. with a patch [2]), BUT I also realized that some
different,
> > inconsistent behavior is possible because of that change.
> >
> > First, the folding optimization part, which I don't know if you'll want
to
> > use (though it seems pretty simple/safe to apply at any time), does the
same
> > thing as Nuno's patch, but with a different implementation. This is
even
> > more of an optimization when combined with constant substitution, for
ORing
> > function flags, etc.
> >
> > At the time, one of the objections (?) was that it didn't allow the same
> > constant expressions to initialize static variables and class
> > members/constants. (Though I don't see much relation: hidden, internal
> > optimization vs. actual syntax change/enhancement.) So I also added
support
> > for arithmetic, bitwise, and concatenation operators (not logical or
> > comparison) in that context. Anyway, should be fairly simple to
> > understand... :-)
> >
> > Now, the different, inconsistent behavior that's possible after the
constant
> > substitution change. This code, for example:
> >
> > function foo() {
> > static $a = -PHP_INT_MAX;
> > }
> >
> > Would have previously given "Unsupported operand types". Now it can
work
> > because the value of PHP_INT_MAX may be substituted first. Fine, good;
> > except that it won't be substituted if it's in a namespace or
> > ZEND_COMPILE_NO_CONSTANT_SUBSTITUTION is set, and then the error occurs.
> >
> > I thought the best solution was to disallow constants in a
"static_scalar"
> > expression (e.g. only literals). This shouldn't break anything unless
> > someone was using - or + signs on TRUE/FALSE/NULL. :-O That will cause
a
> > parse error with my changes. Also:
> >
> > function foo() {
> > static $a = -'abc'; // 0
> > static $b = +'abc'; // abc
> > $c = +'abc'; // 0
> > }
> >
> > So I made the static_scalar unary + operator "do something" and behave
like
> > the regular one. Again, shouldn't break anything unless someone was
> > applying + to literal strings or arrays!
> >
> > Full patch with constant folding, etc.
> > http://realplain.com/php/const_folding.diff
> > http://realplain.com/php/const_folding_5_3.diff
> >
> > -OR-, basic patch only containing the fix for signed static scalars, and
> > only an optimization to save the opcode for unary - and + applied to a
> > constant value (e.g. negative numbers, primarily):
> > http://realplain.com/php/signed_expr_tweaks.diff
> > http://realplain.com/php/signed_expr_tweaks_5_3.diff
> >
> >
> > Thoughts...? Thanks,
> > Matt
> >
> >
> > [1] http://marc.info/?l=php-internals&m=118925033731019&w=2
> > [2] http://web.ist.utl.pt/nuno.lopes/zend_constant_folding.txt
> >
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