Bug#45288: pb2 returns a lot of compilation warnings on linux

Fix warnings flagged by the new warning option -Wunused-but-set-variable
that was added to GCC 4.6 and that is enabled by -Wunused and -Wall. The
option causes a warning whenever a local variable is assigned to but is
later unused. It also warns about meaningless pointer dereferences.

client/mysql.cc:
  Meaningless pointer dereferences.
client/mysql_upgrade.c:
  Check whether reading from the file succeeded.
extra/comp_err.c:
  Unused.
extra/yassl/src/yassl_imp.cpp:
  Skip instead of reading data that is discarded.
include/my_pthread.h:
  Variable is only used in debug builds.
include/mysys_err.h:
  Add new error messages.
mysys/errors.c:
  Add new error message for permission related functions.
mysys/mf_iocache.c:
  Variable is only checked under THREAD.
mysys/my_copy.c:
  Raise a error if chmod or chown fails.
mysys/my_redel.c:
  Raise a error if chmod or chown fails.
regex/engine.c:
  Use a equivalent variable for the assert.
server-tools/instance-manager/instance_options.cc:
  Unused.
sql/field.cc:
  Unused.
sql/item.cc:
  Unused.
sql/log.cc:
  Do not ignore the return value of freopen: only set buffer if
  reopening succeeds.
  
  Adjust doxygen comment to the right function.
  
  Pass message lenght to log function.
sql/mysqld.cc:
  Do not ignore the return value of freopen: only set buffer if
  reopening succeeds.
sql/partition_info.cc:
  Unused.
sql/slave.cc:
  No need to set pointer to the address of '\0'.
sql/spatial.cc:
  Unused. Left for historical purposes.
sql/sql_acl.cc:
  Unused.
sql/sql_base.cc:
  Pointers are always set to the same variables.
sql/sql_parse.cc:
  End statement if reading fails.
  
  Store the buffer after it has actually been updated.
sql/sql_repl.cc:
  No need to set pointer to the address of '\0'.
sql/sql_show.cc:
  Put variable under the same ifdef block.
sql/udf_example.c:
  Set null pointer flag appropriately.
storage/csv/ha_tina.cc:
  Meaningless dereferences.
storage/example/ha_example.cc:
  Return the error since it's available.
storage/myisam/mi_locking.c:
  Remove unused and dead code.

1 files changed, 4 insertions, 10 deletions

diff --git a/sql/sql_base.cc b/sql/sql_base.cc
index d2392bdd9b1..c38526a6d0b 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -5674,7 +5674,7 @@ static void update_field_dependencies(THD *thd, Field *field, TABLE *table)
   DBUG_ENTER("update_field_dependencies");
   if (thd->mark_used_columns != MARK_COLUMNS_NONE)
   {
-    MY_BITMAP *current_bitmap, *other_bitmap;
+    MY_BITMAP *bitmap;
 
     /*
       We always want to register the used keys, as the column bitmap may have
@@ -5685,15 +5685,9 @@ static void update_field_dependencies(THD *thd, Field *field, TABLE *table)
     table->merge_keys.merge(field->part_of_key);
 
     if (thd->mark_used_columns == MARK_COLUMNS_READ)
-    {
-      current_bitmap= table->read_set;
-      other_bitmap=   table->write_set;
-    }
+      bitmap= table->read_set;
     else
-    {
-      current_bitmap= table->write_set;
-      other_bitmap=   table->read_set;
-    }
+      bitmap= table->write_set;
 
     /* 
        The test-and-set mechanism in the bitmap is not reliable during
@@ -5702,7 +5696,7 @@ static void update_field_dependencies(THD *thd, Field *field, TABLE *table)
        only those columns that are used in the SET clause. I.e they are being
        set here. See multi_update::prepare()
     */
-    if (bitmap_fast_test_and_set(current_bitmap, field->field_index))
+    if (bitmap_fast_test_and_set(bitmap, field->field_index))
     {
       if (thd->mark_used_columns == MARK_COLUMNS_WRITE)
       {