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Date: Wed, 13 Jun 2012 00:06:44 +0200
Message-ID: <CAF+90c8brsp=7ZhGLqSBFJ3fEkN9hwhxw6C3fW73x9gO26eXWQ@mail.gmail.com>
To: =?ISO-8859-1?Q?=C1ngel_Gonz=E1lez?= <keisial@gmail.com>
Cc: Tom Boutell <tom@punkave.com>, ab@php.net, Laruence <laruence@php.net>, 
	PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Generators in PHP
From: nikita.ppv@googlemail.com (Nikita Popov)

On Tue, Jun 12, 2012 at 11:07 PM, =C1ngel Gonz=E1lez <keisial@gmail.com> wr=
ote:
> On 11/06/12 23:12, Tom Boutell wrote:
>> Can you really use setjmp and longjmp in that way safely? I thought it
>> was only safe to longjmp "back," not "forward" - you can use them to
>> fake exception support but that's it because you'll smash the stack
>> otherwise. Something like that...
> My first reaction was also "How do you return to the mid-running function=
?"
>
> However, given that the running function is in PHP-land, I think you coul=
d
> (in non-zts, it's direct in zts), save EG() contents and replace with
> new values, and then continue the execution.
That's how it is currently implemented. The generator backs up the
current execution context (execute_data, CVs, Ts), pushed stack
arguments and several executor globals. When the generator is resumed
everything is restored and it continues to run as if nothing happened
:)

Doing context switching using setjmp family functions seems to me like
a really scary thing to do. I don't think that one can do that in a
sane way.

Nikita