Allowing GC in Allegro CL SMP during foreign function calls

[Felix Filozov]

I've created a pull request https://github.com/cffi/cffi/pull/27.


On Tue, Jul 30, 2013 at 11:23 PM, Felix Filozov <ffilozov at gmail.com> wrote:

> Having had a closer look at the code, I noticed that the
> with-foreign-pointer macro allocates in a static area if #+(version>= 8
> 1).
>
> Perhaps it's better to add additional calls to #+(version>= 8 1) in the
> %foreign-funcall macro, and the defcfun-helper-forms function, so that if #+(version>=
> 8 1) the appropriate options are set to allow for GC to run during foreign
> function execution.
>
>
> On Tue, Jul 30, 2013 at 5:33 PM, Felix Filozov <ffilozov at gmail.com> wrote:
>
>> Hi all,
>>
>> When defining a foreign function using def-foreign-call, there's an
>> option one could set called :allow-gc. Setting it to :always, allows the
>> garbage collector to run while the foreign function is executing.
>>
>> At the moment CFFI uses the default value for :allow-gc, which is :never.
>> This prevents GC from running when a foreign function is executing.
>>
>> Moreover, once GC blocks, other processes can't make progress. In my
>> case, I need GC to run during foreign function execution.
>>
>> What do you think about extending the defcfun and foreign-call interfaces
>> to allow for native options to be passed? name-and-options could be
>> extended to accept a new argument, :native-args, for example. Then you'd be
>> able to use defcfun as follows:
>>
>> (defcfun ("strlen" :native-args (:allow-gc :always)) :int
>>   (str :string))
>>
>> Another option is to create a global variable that holds native
>> arguments, and def-foreign-call would read this directly.
>>
>> Thanks,
>> Felix
>>
>
>
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