A fix according to Monty's request:

"uint *errors" is now a non-optional parameter in String:copy()
and copy_and_convert().

sql/field.cc

@@ -531,7 +531,8 @@ int Field_decimal::store(const char *from, uint len, CHARSET_INFO *cs)
   /* Convert character set if the old one is multi byte */
   if (cs->mbmaxlen > 1)
   { 
-    tmp.copy(from, len, cs, &my_charset_bin);
+    uint dummy_errors;
+    tmp.copy(from, len, cs, &my_charset_bin, &dummy_errors);
     from= tmp.ptr();
     len=  tmp.length();
   }
@@ -5502,7 +5503,8 @@ int Field_enum::store(const char *from,uint length,CHARSET_INFO *cs)
   /* Convert character set if nesessary */
   if (String::needs_conversion(length, cs, field_charset, &not_used))
   { 
-    tmpstr.copy(from, length, cs, field_charset);
+    uint dummy_errors;
+    tmpstr.copy(from, length, cs, field_charset, &dummy_errors);
     from= tmpstr.ptr();
     length=  tmpstr.length();
   }
@@ -5650,10 +5652,11 @@ void Field_enum::sql_type(String &res) const
   bool flag=0;
   for (const char **pos= typelib->type_names; *pos; pos++)
   {
+    uint dummy_errors;
     if (flag)
       res.append(',');
     /* convert to res.charset() == utf8, then quote */
-    enum_item.copy(*pos, strlen(*pos), charset(), res.charset());
+    enum_item.copy(*pos, strlen(*pos), charset(), res.charset(), &dummy_errors);
     append_unescaped(&res, enum_item.ptr(), enum_item.length());
     flag= 1;
   }
@@ -5684,7 +5687,8 @@ int Field_set::store(const char *from,uint length,CHARSET_INFO *cs)
   /* Convert character set if nesessary */
   if (String::needs_conversion(length, cs, field_charset, &not_used_offset))
   { 
-    tmpstr.copy(from, length, cs, field_charset);
+    uint dummy_errors;
+    tmpstr.copy(from, length, cs, field_charset, &dummy_errors);
     from= tmpstr.ptr();
     length=  tmpstr.length();
   }
@@ -5760,10 +5764,11 @@ void Field_set::sql_type(String &res) const
   bool flag=0;
   for (const char **pos= typelib->type_names; *pos; pos++)
   {
+    uint dummy_errors;
     if (flag)
       res.append(',');
     /* convert to res.charset() == utf8, then quote */
-    set_item.copy(*pos, strlen(*pos), charset(), res.charset());
+    set_item.copy(*pos, strlen(*pos), charset(), res.charset(), &dummy_errors);
     append_unescaped(&res, set_item.ptr(), set_item.length());
     flag= 1;
   }

sql/item.cc

@@ -818,7 +818,9 @@ bool Item_param::set_str(const char *str, ulong length)
     Assign string with no conversion: data is converted only after it's
     been written to the binary log.
   */
-  if (str_value.copy(str, length, &my_charset_bin, &my_charset_bin))
+  uint dummy_errors;
+  if (str_value.copy(str, length, &my_charset_bin, &my_charset_bin,
+                     &dummy_errors))
     DBUG_RETURN(TRUE);
   state= STRING_VALUE;
   maybe_null= 0;

sql/item_cmpfunc.cc

@@ -1832,8 +1832,9 @@ void Item_func_in::fix_length_and_dec()
         {
           Item_string *conv;
           String tmp, cstr, *ostr= arg[0]->val_str(&tmp);
+          uint dummy_errors;
           cstr.copy(ostr->ptr(), ostr->length(), ostr->charset(),
-                    cmp_collation.collation);
+                    cmp_collation.collation, &dummy_errors);
           conv= new Item_string(cstr.ptr(),cstr.length(), cstr.charset(),
                                 arg[0]->collation.derivation);
           conv->str_value.copy();

sql/item_create.cc

@@ -377,7 +377,10 @@ Item *create_func_space(Item *a)
   {
     sp= new Item_string("",0,cs);
     if (sp)
-      sp->str_value.copy(" ",1,&my_charset_latin1,cs);
+    {
+      uint dummy_errors;
+      sp->str_value.copy(" ", 1, &my_charset_latin1, cs, &dummy_errors);
+    }
   }
   else
   {

sql/item_func.cc

@@ -2906,8 +2906,9 @@ void Item_func_match::init_search(bool no_order)
 
   if (ft_tmp->charset() != cmp_collation.collation)
   {
+    uint dummy_errors;
     search_value.copy(ft_tmp->ptr(), ft_tmp->length(), ft_tmp->charset(),
-                      cmp_collation.collation);
+                      cmp_collation.collation, &dummy_errors);
     ft_tmp= &search_value;
   }
 

sql/item_strfunc.cc

@@ -2160,13 +2160,14 @@ String *Item_func_conv_charset::val_str(String *str)
 {
   DBUG_ASSERT(fixed == 1);
   String *arg= args[0]->val_str(str);
+  uint dummy_errors;
   if (!arg)
   {
     null_value=1;
     return 0;
   }
   null_value= str_value.copy(arg->ptr(),arg->length(),arg->charset(),
-                             conv_charset);
+                             conv_charset, &dummy_errors);
   return null_value ? 0 : &str_value;
 }
 
@@ -2249,11 +2250,12 @@ String *Item_func_charset::val_str(String *str)
 {
   DBUG_ASSERT(fixed == 1);
   String *res = args[0]->val_str(str);
+  uint dummy_errors;
 
   if ((null_value=(args[0]->null_value || !res->charset())))
     return 0;
   str->copy(res->charset()->csname,strlen(res->charset()->csname),
-	    &my_charset_latin1, collation.collation);
+	    &my_charset_latin1, collation.collation, &dummy_errors);
   return str;
 }
 
@@ -2261,11 +2263,12 @@ String *Item_func_collation::val_str(String *str)
 {
   DBUG_ASSERT(fixed == 1);
   String *res = args[0]->val_str(str);
+  uint dummy_errors;
 
   if ((null_value=(args[0]->null_value || !res->charset())))
     return 0;
   str->copy(res->charset()->name,strlen(res->charset()->name),
-	    &my_charset_latin1, collation.collation);
+	    &my_charset_latin1, collation.collation, &dummy_errors);
   return str;
 }
 

sql/item_timefunc.cc

@@ -2121,8 +2121,10 @@ String *Item_char_typecast::val_str(String *str)
   else
   {
     // Convert character set if differ
+    uint dummy_errors;
     if (!(res1= args[0]->val_str(&tmp_value)) ||
-	str->copy(res1->ptr(), res1->length(),res1->charset(), cast_cs))
+	str->copy(res1->ptr(), res1->length(), res1->charset(),
+                  cast_cs, &dummy_errors))
     {
       null_value= 1;
       return 0;

sql/protocol.cc

@@ -713,7 +713,8 @@ bool Protocol::store_string_aux(const char *from, uint length,
       fromcs != &my_charset_bin &&
       tocs != &my_charset_bin)
   {
-    return convert->copy(from, length, fromcs, tocs) ||
+    uint dummy_errors;
+    return convert->copy(from, length, fromcs, tocs, &dummy_errors) ||
            net_store_data(convert->ptr(), convert->length());
   }
   return net_store_data(from, length);

sql/sql_class.cc

@@ -508,13 +508,14 @@ bool THD::convert_string(LEX_STRING *to, CHARSET_INFO *to_cs,
 {
   DBUG_ENTER("convert_string");
   size_s new_length= to_cs->mbmaxlen * from_length;
+  uint dummy_errors;
   if (!(to->str= alloc(new_length+1)))
   {
     to->length= 0;				// Safety fix
     DBUG_RETURN(1);				// EOM
   }
   to->length= copy_and_convert((char*) to->str, new_length, to_cs,
-			       from, from_length, from_cs);
+			       from, from_length, from_cs, &dummy_errors);
   to->str[to->length]=0;			// Safety
   DBUG_RETURN(0);
 }
@@ -537,7 +538,8 @@ bool THD::convert_string(LEX_STRING *to, CHARSET_INFO *to_cs,
 
 bool THD::convert_string(String *s, CHARSET_INFO *from_cs, CHARSET_INFO *to_cs)
 {
-  if (convert_buffer.copy(s->ptr(), s->length(), from_cs, to_cs))
+  uint dummy_errors;
+  if (convert_buffer.copy(s->ptr(), s->length(), from_cs, to_cs, &dummy_errors))
     return TRUE;
   /* If convert_buffer >> s copying is more efficient long term */
   if (convert_buffer.alloced_length() >= convert_buffer.length() * 2 ||

sql/sql_parse.cc

@@ -882,18 +882,20 @@ static int check_connection(THD *thd)
   /* Since 4.1 all database names are stored in utf8 */
   if (db)
   {
+    uint dummy_errors;
     db_buff[copy_and_convert(db_buff, sizeof(db_buff)-1,
                              system_charset_info,
                              db, strlen(db),
-                             thd->charset())]= 0;
+                             thd->charset(), &dummy_errors)]= 0;
     db= db_buff;
   }
 
   if (user)
   {
+    uint dummy_errors;
     user_buff[copy_and_convert(user_buff, sizeof(user_buff)-1,
 			       system_charset_info, user, strlen(user),
-			       thd->charset())]= '\0';
+			       thd->charset(), &dummy_errors)]= '\0';
     user= user_buff;
   }
 
@@ -1380,9 +1382,10 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
     }
 #endif
     /* Convert database name to utf8 */
+    uint dummy_errors;
     db_buff[copy_and_convert(db_buff, sizeof(db_buff)-1,
                              system_charset_info, db, strlen(db),
-                             thd->charset())]= 0;
+                             thd->charset(), &dummy_errors)]= 0;
     db= db_buff;
 
     /* Save user and privileges */
@@ -2066,8 +2069,12 @@ mysql_execute_command(THD *thd)
       }
 
       if (need_conversion)
-        query_len= copy_and_convert(query_str, query_len, to_cs, pstr->ptr(),
-                                    pstr->length(), pstr->charset());
+      {
+        uint dummy_errors;
+        query_len= copy_and_convert(query_str, query_len, to_cs,
+                                    pstr->ptr(), pstr->length(),
+                                    pstr->charset(), &dummy_errors);
+      }
       else
         memcpy(query_str, pstr->ptr(), pstr->length());
       query_str[query_len]= 0;

sql/sql_show.cc

@@ -752,8 +752,9 @@ mysqld_show_fields(THD *thd, TABLE_LIST *table_list,const char *wild,
           String def(tmp1,sizeof(tmp1), system_charset_info);
           type.set(tmp, sizeof(tmp), field->charset());
           field->val_str(&type);
+          uint dummy_errors;
           def.copy(type.ptr(), type.length(), type.charset(), 
-                   system_charset_info);
+                   system_charset_info, &dummy_errors);
           protocol->store(def.ptr(), def.length(), def.charset());
         }
         else if (field->unireg_check == Field::NEXT_NUMBER ||
@@ -1338,9 +1339,10 @@ store_create_info(THD *thd, TABLE *table, String *packet)
 	if (type.length())
 	{
 	  String def_val;
+          uint dummy_errors;
 	  /* convert to system_charset_info == utf8 */
 	  def_val.copy(type.ptr(), type.length(), field->charset(),
-		       system_charset_info);
+		       system_charset_info, &dummy_errors);
           append_unescaped(packet, def_val.ptr(), def_val.length());
 	}
         else

sql/sql_string.cc

@@ -121,12 +121,13 @@ bool String::set(ulonglong num, CHARSET_INFO *cs)
 bool String::set(double num,uint decimals, CHARSET_INFO *cs)
 {
   char buff[331];
+  uint dummy_errors;
 
   str_charset=cs;
   if (decimals >= NOT_FIXED_DEC)
   {
     uint32 len= my_sprintf(buff,(buff, "%.14g",num));// Enough for a DATETIME
-    return copy(buff, len, &my_charset_latin1, cs);
+    return copy(buff, len, &my_charset_latin1, cs, &dummy_errors);
   }
 #ifdef HAVE_FCONVERT
   int decpt,sign;
@@ -191,7 +192,8 @@ end:
 #else
   sprintf(buff,"%.*f",(int) decimals,num);
 #endif
-  return copy(buff,(uint32) strlen(buff), &my_charset_latin1, cs);
+  return copy(buff,(uint32) strlen(buff), &my_charset_latin1, cs,
+              &dummy_errors);
 #endif
 }
 
@@ -336,13 +338,11 @@ bool String::copy(const char *str, uint32 arg_length,
   uint32 offset;
   if (!needs_conversion(arg_length, from_cs, to_cs, &offset))
   {
-    if (errors)
     *errors= 0;
     return copy(str, arg_length, to_cs);
   }
   if ((from_cs == &my_charset_bin) && offset)
   {
-    if (errors)
     *errors= 0;
     return copy_aligned(str, arg_length, offset, to_cs);
   }
@@ -382,7 +382,8 @@ bool String::set_ascii(const char *str, uint32 arg_length)
     set(str, arg_length, str_charset);
     return 0;
   }
-  return copy(str, arg_length, &my_charset_latin1, str_charset);
+  uint dummy_errors;
+  return copy(str, arg_length, &my_charset_latin1, str_charset, &dummy_errors);
 }
 
 
@@ -436,10 +437,12 @@ bool String::append(const char *s,uint32 arg_length)
   if (str_charset->mbminlen > 1)
   {
     uint32 add_length=arg_length * str_charset->mbmaxlen;
+    uint dummy_errors;
     if (realloc(str_length+ add_length))
       return TRUE;
     str_length+= copy_and_convert(Ptr+str_length, add_length, str_charset,
-				  s, arg_length, &my_charset_latin1);
+				  s, arg_length, &my_charset_latin1,
+                                  &dummy_errors);
     return FALSE;
   }
 
@@ -476,10 +479,11 @@ bool String::append(const char *s,uint32 arg_length, CHARSET_INFO *cs)
   if (needs_conversion(arg_length, cs, str_charset, &dummy_offset))
   {
     uint32 add_length= arg_length / cs->mbminlen * str_charset->mbmaxlen;
+    uint dummy_errors;
     if (realloc(str_length + add_length)) 
       return TRUE;
     str_length+= copy_and_convert(Ptr+str_length, add_length, str_charset,
-				  s, arg_length, cs);
+				  s, arg_length, cs, &dummy_errors);
   }
   else
   {
@@ -816,7 +820,6 @@ outp:
     else
       break;
   }
-  if (errors)
   *errors= error_count;
   return (uint32) (to - to_start);
 }

sql/sql_string.h

@@ -29,7 +29,7 @@ int sortcmp(const String *a,const String *b, CHARSET_INFO *cs);
 String *copy_if_not_alloced(String *a,String *b,uint32 arg_length);
 uint32 copy_and_convert(char *to, uint32 to_length, CHARSET_INFO *to_cs,
 			const char *from, uint32 from_length,
-			CHARSET_INFO *from_cs, uint *errors= 0);
+			CHARSET_INFO *from_cs, uint *errors);
 
 class String
 {
@@ -199,7 +199,7 @@ public:
 		    CHARSET_INFO *cs);
   bool set_or_copy_aligned(const char *s, uint32 arg_length, CHARSET_INFO *cs);
   bool copy(const char*s,uint32 arg_length, CHARSET_INFO *csfrom,
-	    CHARSET_INFO *csto, uint *errors= 0);
+	    CHARSET_INFO *csto, uint *errors);
   bool append(const String &s);
   bool append(const char *s);
   bool append(const char *s,uint32 arg_length);

sql/thr_malloc.cc

@@ -108,8 +108,11 @@ char *sql_strmake_with_convert(const char *str, uint32 arg_length,
     memcpy(pos, str, new_length);
   }
   else
+  {
+    uint dummy_errors;
     new_length= copy_and_convert((char*) pos, new_length, to_cs, str,
-				 arg_length, from_cs);
+				 arg_length, from_cs, &dummy_errors);
+  }
   pos[new_length]= 0;
   *result_length= new_length;
   return pos;