Bug#12727287: Maintainer mode compilation fails with gcc 4.6

GCC 4.6 has new -Wunused-but-set-variable flag, which is enabled
by -Wall, that causes GCC to emit a warning whenever a local variable
is assigned to, but otherwise unused (aside from its declaration).

Since the maintainer mode uses -Wall and -Werror, source code which
triggers these warnings will be rejected. That is, these warnings
become hard errors.

The solution is to fix the code which triggers these specific warnings.
In most of the cases, this is a welcome cleanup as code which triggers
this warning is probably dead anyway.

dbug/dbug.c:
  Unused but set.
libmysqld/lib_sql.cc:
  Length is not necessary as the converted error message is always
  null-terminated.
sql/item_func.cc:
  Make get_var_with_binlog private to this compilation unit.
  If a error was raised, do not attempt to evaluate the user
  variable as the statement execution will be interrupted
  anyway.
sql/mysqld.cc:
  Use a void expression to silence the warning. Avoids the use of
  macros that would make the code more unreadable than it already is.
sql/protocol.cc:
  Length is not necessary as the converted error message is always
  null-terminated. Remove unnecessary casts and assignment.
sql/sql_class.h:
  Function is only used in a single compilation unit.
sql/sql_load.cc:
  Only use the variable outside of EMBEDDED_LIBRARY.
storage/innobase/btr/btr0cur.c:
  Do not retrieve field, only the record length is being used.
storage/perfschema/pfs.cc:
  Use a void expression to silence the warning.
tests/mysql_client_test.c:
  Unused but set.
unittest/mysys/lf-t.c:
  Unused but set.

dbug/dbug.c

@@ -1873,7 +1873,6 @@ static void DBUGOpenFile(CODE_STATE *cs,
                          const char *name,const char *end,int append)
 {
   REGISTER FILE *fp;
-  REGISTER BOOLEAN newfile;
 
   if (name != NULL)
   {
@@ -1902,7 +1901,6 @@ static void DBUGOpenFile(CODE_STATE *cs,
       }
       else
       {
-        newfile= !EXISTS(name);
         if (!(fp= fopen(name, append ? "a+" : "w")))
         {
           (void) fprintf(stderr, ERR_OPEN, cs->process, name);

libmysqld/lib_sql.cc

@@ -1144,8 +1144,7 @@ bool net_send_error_packet(THD *thd, uint sql_errno, const char *err,
                            const char *sqlstate)
 {
   uint error;
-  uchar converted_err[MYSQL_ERRMSG_SIZE];
-  uint32 converted_err_len;
+  char converted_err[MYSQL_ERRMSG_SIZE];
   MYSQL_DATA *data= thd->cur_data;
   struct embedded_query_result *ei;
 
@@ -1160,12 +1159,12 @@ bool net_send_error_packet(THD *thd, uint sql_errno, const char *err,
 
   ei= data->embedded_info;
   ei->last_errno= sql_errno;
-  converted_err_len= convert_error_message((char*)converted_err,
-                                           sizeof(converted_err),
-                                           thd->variables.character_set_results,
-                                           err, strlen(err),
-                                           system_charset_info, &error);
-  strmake(ei->info, (const char*) converted_err, sizeof(ei->info)-1);
+  convert_error_message(converted_err, sizeof(converted_err),
+                        thd->variables.character_set_results,
+                        err, strlen(err),
+                        system_charset_info, &error);
+  /* Converted error message is always null-terminated. */
+  strmake(ei->info, converted_err, sizeof(ei->info)-1);
   strmov(ei->sqlstate, sqlstate);
   ei->server_status= thd->server_status;
   thd->cur_data= 0;

sql/item_func.cc

@@ -4965,8 +4965,9 @@ longlong Item_func_get_user_var::val_int()
 
 */
 
-int get_var_with_binlog(THD *thd, enum_sql_command sql_command,
-                        LEX_STRING &name, user_var_entry **out_entry)
+static int
+get_var_with_binlog(THD *thd, enum_sql_command sql_command,
+                    LEX_STRING &name, user_var_entry **out_entry)
 {
   BINLOG_USER_VAR_EVENT *user_var_event;
   user_var_entry *var_entry;
@@ -5096,7 +5097,7 @@ void Item_func_get_user_var::fix_length_and_dec()
     'var_entry' is NULL only if there occured an error during the call to
     get_var_with_binlog.
   */
-  if (var_entry)
+  if (!error && var_entry)
   {
     m_cached_result_type= var_entry->type;
     unsigned_flag= var_entry->unsigned_flag;

sql/mysqld.cc

@@ -5161,6 +5161,9 @@ void handle_connections_sockets()
 
   DBUG_ENTER("handle_connections_sockets");
 
+  (void) ip_flags;
+  (void) socket_flags;
+
 #ifndef HAVE_POLL
   FD_ZERO(&clientFDs);
 #endif

sql/protocol.cc

@@ -368,9 +368,8 @@ bool net_send_error_packet(THD *thd, uint sql_errno, const char *err,
     buff[]: sql_errno:2 + ('#':1 + SQLSTATE_LENGTH:5) + MYSQL_ERRMSG_SIZE:512
   */
   uint error;
-  uchar converted_err[MYSQL_ERRMSG_SIZE];
-  uint32 converted_err_len;
-  uchar buff[2+1+SQLSTATE_LENGTH+MYSQL_ERRMSG_SIZE], *pos;
+  char converted_err[MYSQL_ERRMSG_SIZE];
+  char buff[2+1+SQLSTATE_LENGTH+MYSQL_ERRMSG_SIZE], *pos;
 
   DBUG_ENTER("send_error_packet");
 
@@ -390,19 +389,16 @@ bool net_send_error_packet(THD *thd, uint sql_errno, const char *err,
   {
     /* The first # is to make the protocol backward compatible */
     buff[2]= '#';
-    pos= (uchar*) strmov((char*) buff+3, sqlstate);
+    pos= strmov(buff+3, sqlstate);
   }
 
-  converted_err_len= convert_error_message((char*)converted_err,
-                                           sizeof(converted_err),
-                                           thd->variables.character_set_results,
-                                           err, strlen(err),
-                                           system_charset_info, &error);
-  length= (uint) (strmake((char*) pos, (char*)converted_err,
-                          MYSQL_ERRMSG_SIZE - 1) - (char*) buff);
-  err= (char*) buff;
+  convert_error_message(converted_err, sizeof(converted_err),
+                        thd->variables.character_set_results,
+                        err, strlen(err), system_charset_info, &error);
+  /* Converted error message is always null-terminated. */
+  length= (uint) (strmake(pos, converted_err, MYSQL_ERRMSG_SIZE - 1) - buff);
 
-  DBUG_RETURN(net_write_command(net,(uchar) 255, (uchar*) "", 0, (uchar*) err,
+  DBUG_RETURN(net_write_command(net,(uchar) 255, (uchar*) "", 0, (uchar*) buff,
                                 length));
 }
 

sql/sql_class.h

@@ -3642,14 +3642,6 @@ void add_diff_to_status(STATUS_VAR *to_var, STATUS_VAR *from_var,
                         STATUS_VAR *dec_var);
 void mark_transaction_to_rollback(THD *thd, bool all);
 
-/*
-  This prototype is placed here instead of in item_func.h because it
-  depends on the definition of enum_sql_command, which is in this
-  file.
- */
-int get_var_with_binlog(THD *thd, enum_sql_command sql_command,
-                        LEX_STRING &name, user_var_entry **out_entry);
-
 /* Inline functions */
 
 inline bool add_item_to_list(THD *thd, Item *item)

sql/sql_load.cc

@@ -177,6 +177,7 @@ int mysql_load(THD *thd,sql_exchange *ex,TABLE_LIST *table_list,
 #ifndef EMBEDDED_LIBRARY
   LOAD_FILE_INFO lf_info;
   THD::killed_state killed_status= THD::NOT_KILLED;
+  bool is_concurrent;
 #endif
   char *db = table_list->db;			// This is never null
   /*
@@ -187,7 +188,6 @@ int mysql_load(THD *thd,sql_exchange *ex,TABLE_LIST *table_list,
   char *tdb= thd->db ? thd->db : db;		// Result is never null
   ulong skip_lines= ex->skip_lines;
   bool transactional_table;
-  bool is_concurrent;
   DBUG_ENTER("mysql_load");
 
   /*
@@ -256,7 +256,9 @@ int mysql_load(THD *thd,sql_exchange *ex,TABLE_LIST *table_list,
 
   table= table_list->table;
   transactional_table= table->file->has_transactions();
+#ifndef EMBEDDED_LIBRARY
   is_concurrent= (table_list->lock_type == TL_WRITE_CONCURRENT_INSERT);
+#endif
 
   if (!fields_vars.elements)
   {

storage/innobase/btr/btr0cur.c

@@ -3575,7 +3575,6 @@ static
 void
 btr_record_not_null_field_in_rec(
 /*=============================*/
-	rec_t*		rec,		/*!< in: physical record */
 	ulint		n_unique,	/*!< in: dict_index_get_n_unique(index),
 					number of columns uniquely determine
 					an index entry */
@@ -3595,9 +3594,8 @@ btr_record_not_null_field_in_rec(
 
 	for (i = 0; i < n_unique; i++) {
 		ulint	rec_len;
-		byte*	field;
 
-		field = rec_get_nth_field(rec, offsets, i, &rec_len);
+		rec_get_nth_field_offs(offsets, i, &rec_len);
 
 		if (rec_len != UNIV_SQL_NULL) {
 			n_not_null[i]++;
@@ -3712,7 +3710,7 @@ btr_estimate_number_of_different_key_vals(
 
 			if (n_not_null) {
 				btr_record_not_null_field_in_rec(
-					rec, n_cols, offsets_rec, n_not_null);
+					n_cols, offsets_rec, n_not_null);
 			}
 		}
 
@@ -3747,7 +3745,7 @@ btr_estimate_number_of_different_key_vals(
 
 			if (n_not_null) {
 				btr_record_not_null_field_in_rec(
-					next_rec, n_cols, offsets_next_rec,
+					n_cols, offsets_next_rec,
 					n_not_null);
 			}
 

storage/perfschema/pfs.cc

@@ -1574,6 +1574,9 @@ static void unlock_rwlock_v1(PSI_rwlock *rwlock)
       aggregate_single_stat_chain(&pfs_rwlock->m_read_lock_stat, locked_time);
     }
   }
+#else
+  (void) last_reader;
+  (void) last_writer;
 #endif
 }
 

tests/mysql_client_test.c

@@ -18596,11 +18596,8 @@ static void test_bug38486(void)
 static void test_bug33831(void)
 {
   MYSQL *l_mysql;
-  my_bool error;
 
   DBUG_ENTER("test_bug33831");
-  
-  error= 0;
 
   if (!(l_mysql= mysql_client_init(NULL)))
   {
@@ -18623,9 +18620,8 @@ static void test_bug33831(void)
     DIE_UNLESS(0);
   }
 
-
   mysql_close(l_mysql);
-  
+
   DBUG_VOID_RETURN;
 }
 

unittest/mysys/lf-t.c

@@ -34,8 +34,7 @@ int with_my_thread_init=0;
 */
 pthread_handler_t test_lf_pinbox(void *arg)
 {
-  int    m= *(int *)arg;
-  int32 x= 0;
+  int m= *(int *)arg;
   LF_PINS *pins;
 
   if (with_my_thread_init)
@@ -43,7 +42,7 @@ pthread_handler_t test_lf_pinbox(void *arg)
 
   pins= lf_pinbox_get_pins(&lf_allocator.pinbox);
 
-  for (x= ((int)(intptr)(&m)); m ; m--)
+  for (; m ; m--)
   {
     lf_pinbox_put_pins(pins);
     pins= lf_pinbox_get_pins(&lf_allocator.pinbox);