fixes for the ER_CANT_OPEN_LIBRARY message

sql/share/errmsg.txt:
  .64s is too short for dlerror() messages
sql/sql_plugin.cc:
  1. dlerror() cannot be called twice
  2. remove dlpath from dlerror() messages

sql/share/errmsg.txt

@@ -2981,11 +2981,11 @@ ER_CANT_OPEN_LIBRARY
 	cze "Nemohu otev-Bt sdlenou knihovnu '%-.64s' (errno: %d %s)"
 	dan "Kan ikke bne delt bibliotek '%-.64s' (errno: %d %s)"
 	nla "Kan shared library '%-.64s' niet openen (Errcode: %d %s)"
-	eng "Can't open shared library '%-.64s' (errno: %d %-.64s)"
+	eng "Can't open shared library '%-.64s' (errno: %d %s)"
 	jps "shared library '%-.64s' Jł܂ (errno: %d %s)",
-	est "Ei suuda avada jagatud teeki '%-.64s' (veakood: %d %-.64s)"
+	est "Ei suuda avada jagatud teeki '%-.64s' (veakood: %d %s)"
 	fre "Impossible d'ouvrir la bibliothque partage '%-.64s' (errno: %d %s)"
-	ger "Kann Shared Library '%-.64s' nicht ffnen (Fehler: %d %-.64s)"
+	ger "Kann Shared Library '%-.64s' nicht ffnen (Fehler: %d %s)"
 	greek "      shared library '%-.64s' ( : %d %s)"
 	hun "A(z) '%-.64s' megosztott konyvtar nem hasznalhato (hibakod: %d %s)"
 	ita "Impossibile aprire la libreria condivisa '%-.64s' (errno: %d %s)"
@@ -2995,13 +2995,13 @@ ER_CANT_OPEN_LIBRARY
 	norwegian-ny "Can't open shared library '%-.64s' (errno: %d %s)"
 	pol "Can't open shared library '%-.64s' (errno: %d %s)"
 	por "No pode abrir biblioteca compartilhada '%-.64s' (erro no. '%d' - '%-.64s')"
-	rum "Nu pot deschide libraria shared '%-.64s' (Eroare: %d %-.64s)"
-	rus "    '%-.64s' (: %d %-.64s)"
-	serbian "Ne mogu da otvorim share-ovanu biblioteku '%-.64s' (errno: %d %-.64s)"
+	rum "Nu pot deschide libraria shared '%-.64s' (Eroare: %d %s)"
+	rus "    '%-.64s' (: %d %s)"
+	serbian "Ne mogu da otvorim share-ovanu biblioteku '%-.64s' (errno: %d %s)"
 	slo "Nemem otvori zdiean kninicu '%-.64s' (chybov kd: %d %s)"
 	spa "No puedo abrir libraria conjugada '%-.64s' (errno: %d %s)"
 	swe "Kan inte ppna det dynamiska biblioteket '%-.64s' (Felkod: %d %s)"
-	ukr "  צ Ħ ¦̦ '%-.64s' (: %d %-.64s)"
+	ukr "  צ Ħ ¦̦ '%-.64s' (: %d %s)"
 ER_CANT_FIND_DL_ENTRY  
 	cze "Nemohu naj-Bt funkci '%-.64s' v knihovn"
 	dan "Kan ikke finde funktionen '%-.64s' i bibliotek"

sql/sql_plugin.cc

@@ -105,7 +105,7 @@ static st_plugin_dl *plugin_dl_add(LEX_STRING *dl, int report)
 {
 #ifdef HAVE_DLOPEN
   char dlpath[FN_REFLEN];
-  uint plugin_dir_len, dummy_errors;
+  uint plugin_dir_len, dummy_errors, dlpathlen;
   struct st_plugin_dl *tmp, plugin_dl;
   void *sym;
   DBUG_ENTER("plugin_dl_add");
@@ -133,15 +133,24 @@ static st_plugin_dl *plugin_dl_add(LEX_STRING *dl, int report)
   }
   bzero(&plugin_dl, sizeof(plugin_dl));
   /* Compile dll path */
-  strxnmov(dlpath, sizeof(dlpath) - 1, opt_plugin_dir, "/", dl->str, NullS);
+  dlpathlen=
+    strxnmov(dlpath, sizeof(dlpath) - 1, opt_plugin_dir, "/", dl->str, NullS) -
+    dlpath;
   plugin_dl.ref_count= 1;
   /* Open new dll handle */
   if (!(plugin_dl.handle= dlopen(dlpath, RTLD_NOW)))
   {
+    const char *errmsg=dlerror();
+    if (!strncmp(dlpath, errmsg, dlpathlen))
+    { // if errmsg starts from dlpath, trim this prefix.
+      errmsg+=dlpathlen;
+      if (*errmsg == ':') errmsg++;
+      if (*errmsg == ' ') errmsg++;
+    }
     if (report & REPORT_TO_USER)
-      my_error(ER_CANT_OPEN_LIBRARY, MYF(0), dlpath, errno, dlerror());
+      my_error(ER_CANT_OPEN_LIBRARY, MYF(0), dlpath, errno, errmsg);
     if (report & REPORT_TO_LOG)
-      sql_print_error(ER(ER_CANT_OPEN_LIBRARY), dlpath, errno, dlerror());
+      sql_print_error(ER(ER_CANT_OPEN_LIBRARY), dlpath, errno, errmsg);
     DBUG_RETURN(0);
   }
   /* Determine interface version */