[cffi-devel] Re: Clisp, cffi and defcfuns in a saved image

[Edgar Gonçalves]

Ok, I've just realized that I've been mislocating the problem at
hands. It seems that defcfun works just fine, and the issue I'm
getting resides on the foreign pointers. I've made tests to cffi,
cffi-uffi-compat, ffi (answering to Ken's "CLisp exe vs FFI"
post), and all have worked for a simple function definition/call.
So I delved again to clsql initial situation, and I've traced the
error to a call to %new-environment-handle, that uses a null
pointer as an argument to the ff call to SQLAllocHandle. I also
noticed that the null pointer was indeed showing up at the error
message, so I tried this simple test:

,-----
| (asdf:operate 'asdf:load-op 'cffi)
| (asdf:operate 'asdf:load-op 'cffi-uffi-compat)
| (defvar my-null-ptr (ffi:unsigned-foreign-address 0))
| (format t "- Before loading image, null ptr is: ~A!~%" my-null-ptr)
| (ext:saveinitmem "test.exe"
| 		 :init-function #'(lambda ()
| 				    (format t "- After loading image, my-null-ptr yelds: ~A.~%"
my-null-ptr)
| 				    (ext:quit))
| 		 :NORC t
| 		 :script t
| 		 :executable t
| 		 :quiet t)
`-----


The output I get when I run this code is (after the initial load messages),
,-----
| (...)
| - Before loading image, null ptr is: #<FOREIGN-ADDRESS #x00000000>!
| C:\dev\test>test
| test
| - After loading image, my-null-ptr yelds: #<INVALID FOREIGN-ADDRESS
#x00000000>.
`-----

What makes a foreign address valid or invalid? Is there some way
I can validate a simple null pointer? I could understand if a
given non-null pointer in C would be hard to validate after
restarting an image, but a null pointer is, and always will be,
0x0, right?

-- 
Edgar Gonçalves
  Instituto Superior Técnico,
  INESC-ID - Software Engineering Group,
  Portugal


On 2/13/07, Edgar Gonçalves <edgar.goncalves at gmail.com> wrote:
> On 2/13/07, Edgar Gonçalves <edgar.goncalves at gmail.com> wrote:
> > I'll try again making it work with my clsql project, and I'll post
> > back my success.
> >
>
> Eh, guess not, after all. The problem seems to reside somewhere betwee
> clsql-odbc and CFFI's uffi-compat.lisp.
>
> The following is related to the initialization function of the saved
> image. It assumes the cl-sql library was already loaded AND used
> properly before the image was saved.
>
> What I do before using the foreign functions is to call
> (clsql-sys:database-type-load-foreign :odbc), and this calls
> uffi:load-foreign-library, defined in cffi's uffi-compat.lisp, with
> the odbc32.dll filename. This, by its turn, calls
> cffi:load-foreign-library, which is the same as to call
> cffi::use-foreign-library. So, even though the result should
> apparently be the same, I still get this:
>
> ** - Continuable Error
> FFI::FOREIGN-CALL-OUT: no dynamic object named "SQLAllocHandle" in
> library :DEFAULT
>
> But then again, if I manually call (cffi::use-foreign-library
> "odbc32.dll"), what I get is something different:
>
> *** - FFI::FOREIGN-CALL-OUT: #<INVALID FOREIGN-POINTER #x00000000>
> comes from a previous Lisp session and is
>       invalid
>
> What am I missing here?
>
> --
> Edgar Gonçalves
>