Interpret dynamic library name as literal file name first.

Fixes <https://bugs.gnu.org/21076>.

* libguile/dynl.c (sysdep_dyn_link): Try plain lt_dlopen first, to
  interpret fname as a literal path.
* doc/ref/api-foreign.texi: Update explanation to describe the new
  behavior.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

2 files changed, 11 insertions, 9 deletions

diff --git a/doc/ref/api-foreign.texi b/doc/ref/api-foreign.texi
index d99a33300..b0d6c249b 100644
--- a/doc/ref/api-foreign.texi
+++ b/doc/ref/api-foreign.texi
@@ -75,11 +75,14 @@ Scheme object suitable for representing the linked object file.
 Otherwise an error is thrown.  How object files are searched is system
 dependent.
 
-Normally, @var{library} is just the name of some shared library file
-that will be searched for in the places where shared libraries usually
-reside, such as in @file{/usr/lib} and @file{/usr/local/lib}.
-
-@var{library} should not contain an extension such as @code{.so}.  The
+Guile first tries to load @var{library} as the absolute file name of a shared
+library.  If that fails, it then falls back to interpret
+@var{library} as just the name of some shared library that will be
+searched for in the places where shared libraries usually reside, such
+as @file{/usr/lib} and @file{/usr/local/lib}.
+
+@var{library} should not contain an extension such as @code{.so}, unless
+@var{library} represents the absolute file name to the shared library.  The
 correct file name extension for the host operating system is provided
 automatically, according to libltdl's rules (@pxref{Libltdl interface,
 lt_dlopenext, @code{lt_dlopenext}, libtool, Shared Library Support for
diff --git a/libguile/dynl.c b/libguile/dynl.c
index bf7163c38..e9c03e95b 100644
--- a/libguile/dynl.c
+++ b/libguile/dynl.c
@@ -64,10 +64,9 @@ sysdep_dynl_link (const char *fname, const char *subr)
 {
   lt_dlhandle handle;
 
-  if (fname == NULL)
-    /* Return a handle for the program as a whole.  */
-    handle = lt_dlopen (NULL);
-  else
+  /* Try the literal filename first or, if NULL, the program itself */
+  handle = lt_dlopen (fname);
+  if (handle == NULL)
     {
       handle = lt_dlopenext (fname);