add exception_on_error optional arg to primitive-load-path

* libguile/init.c (scm_load_startup_files): Use
  scm_c_primitive_load_path.

* libguile/load.c (scm_primitive_load_path): Add an optional arg,
  exception_on_error, which if #f will cause primitive-load-path to just
  return #f if no file is found. This is to help out the semantics of
  try-module-autoload. We can't just catch misc-error, because loading
  the file could raise any exception.
  (scm_c_primitive_load_path): Add the extra arg to
  scm_primitive_load_path.

* libguile/load.h: Adapt scm_primitive_load_path prototype.

* module/ice-9/boot-9.scm (try-module-autoload): Refactor slightly to be
  clearer.

libguile/init.c

@@ -282,7 +282,7 @@ scm_load_startup_files ()
   /* Load Ice-9.  */
   if (!scm_ice_9_already_loaded)
     {
-      scm_primitive_load_path (scm_from_locale_string ("ice-9/boot-9"));
+      scm_c_primitive_load_path ("ice-9/boot-9");
 
       /* Load the init.scm file.  */
       if (scm_is_true (init_path))

libguile/load.c

@@ -586,16 +586,21 @@ scm_try_autocompile (SCM source)
   return SCM_BOOL_F;
 }
 
-SCM_DEFINE (scm_primitive_load_path, "primitive-load-path", 1, 0, 0, 
-	    (SCM filename),
+SCM_DEFINE (scm_primitive_load_path, "primitive-load-path", 1, 1, 0, 
+	    (SCM filename, SCM exception_on_not_found),
 	    "Search @var{%load-path} for the file named @var{filename} and\n"
 	    "load it into the top-level environment.  If @var{filename} is a\n"
 	    "relative pathname and is not found in the list of search paths,\n"
-	    "an error is signalled.")
+	    "an error is signalled, unless the optional argument\n"
+            "@var{exception_on_not_found} is @code{#f}, in which case\n"
+            "@code{#f} is returned instead.")
 #define FUNC_NAME s_scm_primitive_load_path
 {
   SCM full_filename, compiled_filename;
 
+  if (SCM_UNBNDP (exception_on_not_found))
+    exception_on_not_found = SCM_BOOL_T;
+
   full_filename = scm_sys_search_load_path (filename);
   compiled_filename = scm_search_path (*scm_loc_load_compiled_path,
                                        filename,
@@ -603,8 +608,13 @@ SCM_DEFINE (scm_primitive_load_path, "primitive-load-path", 1, 0, 0,
                                        SCM_BOOL_T);
 
   if (scm_is_false (full_filename) && scm_is_false (compiled_filename))
+    {
+      if (scm_is_true (exception_on_not_found))
         SCM_MISC_ERROR ("Unable to find file ~S in load path",
                         scm_list_1 (filename));
+      else
+        return SCM_BOOL_F;
+    }
 
   if (scm_is_false (full_filename)
       || (scm_is_true (compiled_filename)
@@ -622,7 +632,8 @@ SCM_DEFINE (scm_primitive_load_path, "primitive-load-path", 1, 0, 0,
 SCM
 scm_c_primitive_load_path (const char *filename)
 {
-  return scm_primitive_load_path (scm_from_locale_string (filename));
+  return scm_primitive_load_path (scm_from_locale_string (filename),
+                                  SCM_BOOL_T);
 }
 
 

libguile/load.h

@@ -33,7 +33,7 @@ SCM_API SCM scm_sys_library_dir (void);
 SCM_API SCM scm_sys_site_dir (void);
 SCM_API SCM scm_search_path (SCM path, SCM filename, SCM exts, SCM require_exts);
 SCM_API SCM scm_sys_search_load_path (SCM filename);
-SCM_API SCM scm_primitive_load_path (SCM filename);
+SCM_API SCM scm_primitive_load_path (SCM filename, SCM exception_on_not_found);
 SCM_API SCM scm_c_primitive_load_path (const char *filename);
 SCM_INTERNAL void scm_init_load_path (void);
 SCM_INTERNAL void scm_init_load (void);

module/ice-9/boot-9.scm

@@ -2270,16 +2270,15 @@ module '(ice-9 q) '(make-q q-length))}."
     (resolve-module dir-hint-module-name #f)
     (and (not (autoload-done-or-in-progress? dir-hint name))
 	 (let ((didit #f))
-	   (define (load-file proc file)
-	     (save-module-excursion (lambda () (proc file)))
-	     (set! didit #t))
 	   (dynamic-wind
 	    (lambda () (autoload-in-progress! dir-hint name))
 	    (lambda ()
 	      (with-fluid* current-reader #f
                 (lambda ()
-                  (load-file primitive-load-path
-                             (in-vicinity dir-hint name)))))
+                  (save-module-excursion
+                   (lambda () 
+                     (primitive-load-path (in-vicinity dir-hint name) #f)
+                     (set! didit #t))))))
 	    (lambda () (set-autoloaded! dir-hint name didit)))
 	   didit))))