Fix native code uneffective loads after recompilation

'dlopen' can return the same handle if two shared with the same
filename are loaded in two different times (even if the first was
deleted!).  To prevent this scenario the last modification time of the
source file is included in the hashing algorithm.

	* src/comp.c (Fcomp_el_to_eln_filename): Update hashing algo to
	include the source last modification date.
	* src/lread.c (maybe_swap_for_eln): Do not check for eln newer
	then elc as this is now unnecessary.

src/comp.c

@@ -3872,13 +3872,26 @@ If BASE-DIR is nil use the first entry in `comp-eln-load-path'.  */)
 {
   CHECK_STRING (filename);
 
+  if (NILP (Ffile_exists_p (filename)))
+    xsignal1 (Qfile_missing, filename);
+
+  Lisp_Object last_mod_time =
+    Fnth (make_fixnum (5), Ffile_attributes (filename, Qnil));
+
   if (suffix_p (filename, ".gz"))
     filename = Fsubstring (filename, Qnil, make_fixnum (-3));
   filename = Fexpand_file_name (filename, Qnil);
 
   /* We create eln filenames with an hash in order to look-up these
      starting from the source filename, IOW have a relation
-     /absolute/path/filename.el -> eln-cache/filename-hash.eln.
+
+     /absolute/path/filename.el + last_mod_time ->
+     eln-cache/filename-hash.eln.
+
+     'dlopen' can return the same handle if two shared with the same
+     filename are loaded in two different times (even if the first was
+     deleted!).  To prevent this scenario the last modification time
+     of the source file is included in the hashing algorithm.
 
      As installing .eln files compiled during the build changes their
      absolute path we need an hashing mechanism that is not sensitive
@@ -3910,7 +3923,9 @@ If BASE-DIR is nil use the first entry in `comp-eln-load-path'.  */)
 	}
     }
 
-  Lisp_Object hash = Fsubstring (comp_hash_string (filename), Qnil,
+  Lisp_Object hash_input =
+    concat2 (filename, Fprin1_to_string (last_mod_time, Qnil));
+  Lisp_Object hash = Fsubstring (comp_hash_string (hash_input), Qnil,
 				 make_fixnum (ELN_FILENAME_HASH_LEN));
   filename = concat2 (Ffile_name_nondirectory (Fsubstring (filename, Qnil,
 							   make_fixnum (-3))),

src/lread.c

@@ -1635,19 +1635,13 @@ maybe_swap_for_eln (Lisp_Object *filename, int *fd, struct timespec mtime)
 	    emacs_close (eln_fd);
 	  else
 	    {
-	      struct timespec eln_mtime = get_stat_mtime (&eln_st);
-	      if (timespec_cmp (eln_mtime, mtime) > 0)
-		{
-		  *filename = eln_name;
-		  emacs_close (*fd);
-		  *fd = eln_fd;
-		  /* Store the eln -> el relation.  */
-		  Fputhash (Ffile_name_nondirectory (eln_name),
-			    el_name, Vcomp_eln_to_el_h);
-		  return;
-		}
-	      else
-		emacs_close (eln_fd);
+	      *filename = eln_name;
+	      emacs_close (*fd);
+	      *fd = eln_fd;
+	      /* Store the eln -> el relation.  */
+	      Fputhash (Ffile_name_nondirectory (eln_name),
+			el_name, Vcomp_eln_to_el_h);
+	      return;
 	    }
 	}
     }