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To: "Andrew Mather" <an.dromeda@btconnect.com>
Cc: <internals@lists.php.net>
References: <200606302354.02272.an.dromeda@btconnect.com> <001301c69cac$39025540$07000100@OHRLVN4523SG> <007701c69cfb$02655ec0$ca5f8a51@VaioCen>
Date: Sat, 1 Jul 2006 09:49:13 -0700
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Subject: Re: TSRMLS_D/C persistence
From: pollita@php.net ("Sara Golemon")

> That also implies then that if I create a handler for eg: an
> external stream/file, and keep it as a singleton instance in the
> extension, then it could be reasonably called by any number
> of different threads.
>
There's a plan B though.

void foo(int bar) { }

foo() doesn't have room for trms_ls in its prototype so it just won't be 
available inside the function right?  Wrong.  Zend exports TSRMLS_FETCH(); 
which can recover (through a slightly expensive process) the thread 
appropriate value for tsrm_ls.  Thus:

void foo(int bar TSRMLS_DC)
{
    somefoo(bar TSRMLS_CC);
}

and

void foo(int bar)
{
    TSRMLS_FETCH();

    somefoo(bar TSRMLS_CC);
}

Are functionally identical.

> ie: any resource callable from a php-extension must be
> thread safe...
>
In order to work in all build environments? Yes.

> Would that be a fair comment? (Means my single-threaded
> data engine prototype is going to need a serious going over).
>
Technically, if you *know* that your php-extension will only ever be used in 
a non-threaded environment (e.g. non-Win32, non-Apache2, 
non-otherThreadedWebSAPI), then you can be "lazy" and not worry about thread 
safety (or tsrm_ls in general).  I would however *strongly recommend* 
reworking your library for thread safety so that this problem doesn't become 
an issue later on.

-Sara