make sql_udf.cc to shorten dlerror() messages

just as sql_plugin.cc does

include/my_sys.h

@@ -998,6 +998,8 @@ void my_uuid(uchar *guid);
 void my_uuid2str(const uchar *guid, char *s);
 void my_uuid_end(void);
 
+const char *my_dlerror(const char *dlpath);
+
 /* character sets */
 extern void my_charset_loader_init_mysys(MY_CHARSET_LOADER *loader);
 extern uint get_charset_number(const char *cs_name, uint cs_flags);

mysys/CMakeLists.txt

@@ -41,7 +41,7 @@ SET(MYSYS_SOURCES  array.c charset-def.c charset.c checksum.c my_default.c
 				my_atomic.c my_getncpus.c my_safehash.c my_chmod.c my_rnd.c
                                 my_uuid.c wqueue.c waiting_threads.c ma_dyncol.c
 				my_rdtsc.c my_context.c psi_noop.c
-                                file_logger.c)
+                                file_logger.c my_dlerror.c)
 
 IF (WIN32)
  SET (MYSYS_SOURCES ${MYSYS_SOURCES} my_winthread.c my_wincond.c my_winerr.c my_winfile.c my_windac.c my_conio.c)

mysys/my_dlerror.c

+/*
+   Copyright (c) 2017, MariaDB
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA */
+
+#include <my_global.h>
+#include <string.h>
+
+const char *my_dlerror(const char *dlpath)
+{
+  const char *errmsg=dlerror();
+  size_t dlpathlen= strlen(dlpath);
+  if (!strncmp(dlpath, errmsg, dlpathlen))
+  { /* if errmsg starts from dlpath, trim this prefix */
+    errmsg+=dlpathlen;
+    if (*errmsg == ':') errmsg++;
+    if (*errmsg == ' ') errmsg++;
+  }
+  return errmsg;
+}

sql/sql_plugin.cc

@@ -723,7 +723,7 @@ static st_plugin_dl *plugin_dl_add(const LEX_STRING *dl, int report)
 {
 #ifdef HAVE_DLOPEN
   char dlpath[FN_REFLEN];
-  uint plugin_dir_len, dummy_errors, dlpathlen, i;
+  uint plugin_dir_len, dummy_errors, i;
   struct st_plugin_dl *tmp= 0, plugin_dl;
   void *sym;
   st_ptr_backup tmp_backup[array_elements(list_of_services)];
@@ -759,15 +759,7 @@ static st_plugin_dl *plugin_dl_add(const LEX_STRING *dl, int report)
   /* Open new dll handle */
   if (!(plugin_dl.handle= dlopen(dlpath, RTLD_NOW)))
   {
-    const char *errmsg=dlerror();
-    dlpathlen= strlen(dlpath);
-    if (!strncmp(dlpath, errmsg, dlpathlen))
-    { // if errmsg starts from dlpath, trim this prefix.
-      errmsg+=dlpathlen;
-      if (*errmsg == ':') errmsg++;
-      if (*errmsg == ' ') errmsg++;
-    }
-    report_error(report, ER_CANT_OPEN_LIBRARY, dlpath, errno, errmsg);
+    report_error(report, ER_CANT_OPEN_LIBRARY, dlpath, errno, my_dlerror(dlpath));
     goto ret;
   }
   dlopen_count++;

sql/sql_udf.cc

@@ -227,14 +227,13 @@ void udf_init()
     if (dl == NULL)
     {
       char dlpath[FN_REFLEN];
-      strxnmov(dlpath, sizeof(dlpath) - 1, opt_plugin_dir, "/", tmp->dl,
-               NullS);
+      strxnmov(dlpath, sizeof(dlpath) - 1, opt_plugin_dir, "/", tmp->dl, NullS);
       (void) unpack_filename(dlpath, dlpath);
       if (!(dl= dlopen(dlpath, RTLD_NOW)))
       {
 	/* Print warning to log */
         sql_print_error(ER_THD(new_thd, ER_CANT_OPEN_LIBRARY),
-                        tmp->dl, errno, dlerror());
+                        tmp->dl, errno, my_dlerror(dlpath));
 	/* Keep the udf in the hash so that we can remove it later */
 	continue;
       }
@@ -538,10 +537,10 @@ int mysql_create_function(THD *thd,udf_func *udf)
 
     if (!(dl = dlopen(dlpath, RTLD_NOW)))
     {
+      my_error(ER_CANT_OPEN_LIBRARY, MYF(0),
+               udf->dl, errno, my_dlerror(dlpath));
       DBUG_PRINT("error",("dlopen of %s failed, error: %d (%s)",
                           udf->dl, errno, dlerror()));
-      my_error(ER_CANT_OPEN_LIBRARY, MYF(0),
-               udf->dl, errno, dlerror());
       goto err;
     }
     new_dl=1;