Steel Bank Common Lisp

On 19 October 2010 13:58, Teemu Likonen <tlikonen@...> wrote:

>    * (ql:quickload "cffi")
>    * (cffi:load-foreign-library "libreadline.so")
>    * (defparameter *lib* *)
>    * (cffi:foreign-funcall "readline" :string "> " :string)
>
>    * (cffi:close-foreign-library *lib*)
>    STYLE-WARNING: Undefined alien: "readline"

> In other words, always when I close a library I get style warnings
> about foreign functions that I have called previously. Why?

Closing the foreign library means calling dlclose(), which means that
the contents of that library/shared object are no longer available.

Trying to call the "readline" again would result in an
UNDEFINED-ALIEN-FUNCTION error.

Hence the style-warning.

(In 99% of usage you should not be closing foreign libraries at all.)

Cheers,

 -- Nikodemus

* 2010-10-19 16:20 (+0300), Nikodemus Siivola wrote:

> Closing the foreign library means calling dlclose(), which means that
> the contents of that library/shared object are no longer available.
>
> Trying to call the "readline" again would result in an
> UNDEFINED-ALIEN-FUNCTION error.
>
> Hence the style-warning.
>
> (In 99% of usage you should not be closing foreign libraries at all.)

OK, thanks. My intent was not to call foreign functions anymore. I was
thinking about loading a library through SB-EXT:*INIT-HOOKS* and closing
it through SB-EXT:*EXIT-HOOKS* but maybe I'll just stop worrying about
closing libraries.

It seems that I don't even have to load libraries every time when
loading an SBCL image. Just load foreign libraries once in the
image-creation session. The saved SBCL image will load foreign libraries
automatically when it's started. This was a bit unexpected but maybe the
saved image is clever enough to know that there is some code that is
using the libraries.

On 19 October 2010 16:54, Teemu Likonen <tlikonen@...> wrote:

> it through SB-EXT:*EXIT-HOOKS* but maybe I'll just stop worrying about
> closing libraries.

SBCL will automatically close all open foreign libraries on normal
exit. (In case they have hooks into dlclose(), which while rare isn't
impossible.)

> It seems that I don't even have to load libraries every time when
> loading an SBCL image. Just load foreign libraries once in the
> image-creation session. The saved SBCL image will load foreign
> libraries automatically when it's started. This was a bit unexpected

If you load a foreign libraries and then save a core, then the same
set of libraries will be loaded on startup -- the assumption is that
they were there for a reason.

Cheers,

 -- Nikodemus

* 2010-10-19 17:14 (+0300), Nikodemus Siivola wrote:

> SBCL will automatically close all open foreign libraries on normal
> exit. (In case they have hooks into dlclose(), which while rare isn't
> impossible.)

> If you load a foreign libraries and then save a core, then the same
> set of libraries will be loaded on startup -- the assumption is that
> they were there for a reason.

That's certainly nice. I thought I had to do all this manually. :-)

Nikodemus Siivola wrote:
> 
> On 19 October 2010 16:54, Teemu Likonen <tlikonen@...> wrote:
> 
> > It seems that I don't even have to load libraries every time when
> > loading an SBCL image. Just load foreign libraries once in the
> > image-creation session. The saved SBCL image will load foreign
> > libraries automatically when it's started. This was a bit unexpected
> 
> If you load a foreign libraries and then save a core, then the same
> set of libraries will be loaded on startup -- the assumption is that
> they were there for a reason.
>

What happens if libraries are absent when the image starts?  My program
want to use a library if present, but if absent then use alternative
(slower) code.


-- 
                              Waldek Hebisch
hebisch@...

Waldek Hebisch <hebisch@...> writes:

> Nikodemus Siivola wrote:
>> 
>> On 19 October 2010 16:54, Teemu Likonen <tlikonen@...> wrote:
>> 
>> > It seems that I don't even have to load libraries every time when
>> > loading an SBCL image. Just load foreign libraries once in the
>> > image-creation session. The saved SBCL image will load foreign
>> > libraries automatically when it's started. This was a bit unexpected
>> 
>> If you load a foreign libraries and then save a core, then the same
>> set of libraries will be loaded on startup -- the assumption is that
>> they were there for a reason.
>>
>
> What happens if libraries are absent when the image starts?  My program
> want to use a library if present, but if absent then use alternative
> (slower) code.
Call sb-alien:load-shared-object with :dont-save T.
-- 
With Best Regards, Stas.

> 
> Waldek Hebisch <hebisch@...> writes:
> 
> > Nikodemus Siivola wrote:
> >> 
> >> If you load a foreign libraries and then save a core, then the same
> >> set of libraries will be loaded on startup -- the assumption is that
> >> they were there for a reason.
> >>
> >
> > What happens if libraries are absent when the image starts?  My program
> > want to use a library if present, but if absent then use alternative
> > (slower) code.
> Call sb-alien:load-shared-object with :dont-save T.

Thanks, but its seems that older sbcl version (for example 1.0.16)
do not support :dont-save.


-- 
                              Waldek Hebisch
hebisch@...

On 30 October 2010 21:42, Waldek Hebisch <hebisch@...> wrote:

> Thanks, but its seems that older sbcl version (for example 1.0.16)
> do not support :dont-save.

Indeed not. 1.0.16 is over two years old, and we don't generally
backport features or bugfixes found in newer versions.

If you need this capability there, you need to look at the sources and
figure out how to hotpatch things. I'll be happy to help you figure
out the details.

If you need help upgrading from 1.0.16, I'll be delighted to assist,
whatever the problems are.

However, if you need a backport or support for old SBCL versions, then
I would suggest looking for a commercial entity like my own
http://sb-studio.net/ to provide them.

Cheers,

 -- Nikodemus