Unable to use libcurl with cffi on Windows 10 - windows

Question

I am playing with the CFFI tutorial on Windows 10 and have installed the libcurl-devel package using msys2. I found a file libcurl.dll.a in the directory c:\msys2\usr\lib\ and added this directory to *foreign-library-directories* using:
(pushnew #P"c:/msys64/usr/lib/" *foreign-library-directories*
:test #'equal)
But if I try (use-foreign-library libcurl) I get the following error:
Unable to load foreign library (LIBCURL).
Error opening shared object "libcurl.dll"
What am I missing? I tried to point to libcurl.dll.a directly but the error stays the same:
(define-foreign-library libcurl
(:darwin (:or "libcurl.3.dylib" "libcurl.dylib"))
(:unix (:or "libcurl.so.3" "libcurl.so"))
(t "libcurl.dll.a"))
Here is the complete code as given in the tutorial:
(asdf:load-system :cffi)
;;; Nothing special about the "CFFI-USER" package. We're just
;;; using it as a substitute for your own CL package.
(defpackage :cffi-user
(:use :common-lisp :cffi))
(in-package :cffi-user)
(pushnew #P"c:/msys64/usr/lib/" *foreign-library-directories*
:test #'equal)
(define-foreign-library libcurl
(:darwin (:or "libcurl.3.dylib" "libcurl.dylib"))
(:unix (:or "libcurl.so.3" "libcurl.so"))
(t (:default "libcurl")))
(use-foreign-library libcurl)
EDIT
I am using SBCL 1.4.16 from the portacle package.
EDIT 2
Just for the sake of completeness. If I change define-foreign-library to
(define-foreign-library libcurl
(:darwin (:or "libcurl.3.dylib" "libcurl.dylib"))
(:unix (:or "libcurl.so.3" "libcurl.so"))
(t "libcurl.dll.a"))
the errors changes:
Unable to load foreign library (LIBCURL).
Error opening shared object "c:\\msys64\\usr\\lib\\libcurl.dll.a":
%1 ist keine zulässige Win32-Anwendung.
As far as I understand at least the file is found but seems not to be in the right format. I didn't find any further information about the difference between dynamic (.dll) and static (.dll.a) files with respect to cffi and don't have the resources at the moment to further investigate this.

Answer 1

Instead of using use-foreign-library, try loading load-foreign-library. It is lower level code, but it will allow you to experiment with files and paths.
Also use cygcheck to figure out what libcurl.dll depends on. Then make sure you have the components installed, and that they are in PATH.
Finally, check where libcurl.dll lives in your MSYS2. On my system it is in /c/msys64/mingw64/bin/libcurl-4.dll