Bug#45288: pb2 returns a lot of compilation warnings

Fix assorted warnings that are generated in optimized builds.
Most of it is silencing variables that are set but unused.

This patch also introduces the MY_ASSERT_UNREACHABLE macro
which helps the compiler to deduce that a certain piece of
code is unreachable.

include/my_compiler.h:
  Use GCC's __builtin_unreachable if available. It allows
  GCC to deduce the unreachability of certain code paths,
  thus avoiding warnings that, for example, accused that a
  variable could be used without being initialized (due to
  unreachable code paths).

18 files changed, 53 insertions, 45 deletions

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index 38862210cba..d790b3f0ee7 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -5258,8 +5258,13 @@ void do_connect(struct st_command *command)
                   opt_charsets_dir);
 
 #ifdef HAVE_OPENSSL
-  if (opt_use_ssl || con_ssl)
+  if (opt_use_ssl)
+    con_ssl= 1;
+#endif
+
+  if (con_ssl)
   {
+#ifdef HAVE_OPENSSL
     mysql_ssl_set(&con_slot->mysql, opt_ssl_key, opt_ssl_cert, opt_ssl_ca,
 		  opt_ssl_capath, opt_ssl_cipher);
 #if MYSQL_VERSION_ID >= 50000
@@ -5268,36 +5273,37 @@ void do_connect(struct st_command *command)
     mysql_options(&con_slot->mysql, MYSQL_OPT_SSL_VERIFY_SERVER_CERT,
                   &opt_ssl_verify_server_cert);
 #endif
-  }
 #endif
+  }
 
-#ifdef __WIN__
   if (con_pipe)
   {
+#ifdef __WIN__
     opt_protocol= MYSQL_PROTOCOL_PIPE;
-  }
 #endif
+  }
 
   if (opt_protocol)
     mysql_options(&con_slot->mysql, MYSQL_OPT_PROTOCOL, (char*) &opt_protocol);
 
-#ifdef HAVE_SMEM
   if (con_shm)
   {
+#ifdef HAVE_SMEM
     uint protocol= MYSQL_PROTOCOL_MEMORY;
     if (!ds_shm.length)
       die("Missing shared memory base name");
     mysql_options(&con_slot->mysql, MYSQL_SHARED_MEMORY_BASE_NAME, ds_shm.str);
     mysql_options(&con_slot->mysql, MYSQL_OPT_PROTOCOL, &protocol);
+#endif
   }
-  else if(shared_memory_base_name)
+#ifdef HAVE_SMEM
+  else if (shared_memory_base_name)
   {
     mysql_options(&con_slot->mysql, MYSQL_SHARED_MEMORY_BASE_NAME,
-      shared_memory_base_name);
+                  shared_memory_base_name);
   }
 #endif
 
-
   /* Use default db name */
   if (ds_database.length == 0)
     dynstr_set(&ds_database, opt_db);
diff --git a/cmd-line-utils/readline/complete.c b/cmd-line-utils/readline/complete.c
index 2745e4e4801..d11ea2493a6 100644
--- a/cmd-line-utils/readline/complete.c
+++ b/cmd-line-utils/readline/complete.c
@@ -1839,8 +1839,11 @@ rl_username_completion_function (text, state)
 #else /* !__WIN32__ && !__OPENNT) */
   static char *username = (char *)NULL;
   static struct passwd *entry;
-  static int namelen, first_char, first_char_loc;
+  static int first_char, first_char_loc;
   char *value;
+#if defined (HAVE_GETPWENT)
+  static int namelen;
+#endif
 
   if (state == 0)
     {
@@ -1850,7 +1853,9 @@ rl_username_completion_function (text, state)
       first_char_loc = first_char == '~';
 
       username = savestring (&text[first_char_loc]);
+#if defined (HAVE_GETPWENT)
       namelen = strlen (username);
+#endif
       setpwent ();
     }
 
diff --git a/cmd-line-utils/readline/histexpand.c b/cmd-line-utils/readline/histexpand.c
index ab8d8ecc866..7b51c369827 100644
--- a/cmd-line-utils/readline/histexpand.c
+++ b/cmd-line-utils/readline/histexpand.c
@@ -693,7 +693,7 @@ history_expand_internal (string, start, end_index_ptr, ret_string, current_line)
 	case 's':
 	  {
 	    char *new_event;
-	    int delimiter, failed, si, l_temp, ws, we;
+	    int delimiter, failed, si, l_temp, we;
 
 	    if (c == 's')
 	      {
@@ -792,7 +792,6 @@ history_expand_internal (string, start, end_index_ptr, ret_string, current_line)
 		  {
 		    for (; temp[si] && whitespace (temp[si]); si++)
 		      ;
-		    ws = si;
 		    we = history_tokenize_word (temp, si);
 		  }
 
diff --git a/cmd-line-utils/readline/histfile.c b/cmd-line-utils/readline/histfile.c
index cbd367542ce..1a6d69b6684 100644
--- a/cmd-line-utils/readline/histfile.c
+++ b/cmd-line-utils/readline/histfile.c
@@ -402,6 +402,7 @@ history_truncate_file (fname, lines)
   if (bp > buffer && ((file = open (filename, O_WRONLY|O_TRUNC|O_BINARY, 0600)) != -1))
     {
       bytes_written= write (file, bp, chars_read - (bp - buffer));
+      (void) bytes_written;
 
 #if defined (__BEOS__)
       /* BeOS ignores O_TRUNC. */
diff --git a/cmd-line-utils/readline/isearch.c b/cmd-line-utils/readline/isearch.c
index 305c847d8da..977e08eb9ba 100644
--- a/cmd-line-utils/readline/isearch.c
+++ b/cmd-line-utils/readline/isearch.c
@@ -617,7 +617,7 @@ rl_search_history (direction, invoking_key)
      int direction, invoking_key __attribute__((unused));
 {
   _rl_search_cxt *cxt;		/* local for now, but saved globally */
-  int c, r;
+  int r;
 
   RL_SETSTATE(RL_STATE_ISEARCH);
   cxt = _rl_isearch_init (direction);
@@ -632,7 +632,7 @@ rl_search_history (direction, invoking_key)
   r = -1;
   for (;;)
     {
-      c = _rl_search_getchar (cxt);
+      _rl_search_getchar (cxt);
       /* We might want to handle EOF here (c == 0) */
       r = _rl_isearch_dispatch (cxt, cxt->lastc);
       if (r <= 0)
@@ -655,9 +655,9 @@ int
 _rl_isearch_callback (cxt)
      _rl_search_cxt *cxt;
 {
-  int c, r;
+  int r;
 
-  c = _rl_search_getchar (cxt);
+  _rl_search_getchar (cxt);
   /* We might want to handle EOF here */
   r = _rl_isearch_dispatch (cxt, cxt->lastc);
 
diff --git a/cmd-line-utils/readline/parens.c b/cmd-line-utils/readline/parens.c
index fe1578ed3e2..58f22291172 100644
--- a/cmd-line-utils/readline/parens.c
+++ b/cmd-line-utils/readline/parens.c
@@ -115,7 +115,7 @@ rl_insert_close (count, invoking_key)
   else
     {
 #if defined (HAVE_SELECT)
-      int orig_point, match_point, ready;
+      int orig_point, match_point;
       struct timeval timer;
       fd_set readfds;
 
@@ -136,7 +136,7 @@ rl_insert_close (count, invoking_key)
       orig_point = rl_point;
       rl_point = match_point;
       (*rl_redisplay_function) ();
-      ready = select (1, &readfds, (fd_set *)NULL, (fd_set *)NULL, &timer);
+      select (1, &readfds, (fd_set *)NULL, (fd_set *)NULL, &timer);
       rl_point = orig_point;
 #else /* !HAVE_SELECT */
       _rl_insert_char (count, invoking_key);
diff --git a/cmd-line-utils/readline/readline.c b/cmd-line-utils/readline/readline.c
index fb92becdbf9..95947551823 100644
--- a/cmd-line-utils/readline/readline.c
+++ b/cmd-line-utils/readline/readline.c
@@ -447,11 +447,10 @@ readline_internal_char ()
 readline_internal_charloop ()
 #endif
 {
-  static int lastc, eof_found;
+  static int lastc;
   int c, code, lk;
 
   lastc = -1;
-  eof_found = 0;
 
 #if !defined (READLINE_CALLBACKS)
   while (rl_done == 0)
diff --git a/cmd-line-utils/readline/text.c b/cmd-line-utils/readline/text.c
index bb0f5d97160..02b28750c86 100644
--- a/cmd-line-utils/readline/text.c
+++ b/cmd-line-utils/readline/text.c
@@ -811,11 +811,10 @@ _rl_overwrite_char (count, c)
   int i;
 #if defined (HANDLE_MULTIBYTE)
   char mbkey[MB_LEN_MAX];
-  int k;
 
   /* Read an entire multibyte character sequence to insert COUNT times. */
   if (count > 0 && MB_CUR_MAX > 1 && rl_byte_oriented == 0)
-    k = _rl_read_mbstring (c, mbkey, MB_LEN_MAX);
+    _rl_read_mbstring (c, mbkey, MB_LEN_MAX);
 #endif
 
   rl_begin_undo_group ();
diff --git a/include/my_compiler.h b/include/my_compiler.h
index 1cd46ff4260..c7d334999d0 100644
--- a/include/my_compiler.h
+++ b/include/my_compiler.h
@@ -32,8 +32,15 @@
 
 /* GNU C/C++ */
 #if defined __GNUC__
+/* Convenience macro to test the minimum required GCC version. */
+# define MY_GNUC_PREREQ(maj, min) \
+    ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
 /* Any after 2.95... */
 # define MY_ALIGN_EXT
+/* Comunicate to the compiler the unreachability of the code. */
+# if MY_GNUC_PREREQ(4,5)
+#   define MY_ASSERT_UNREACHABLE()   __builtin_unreachable()
+# endif
 
 /* Microsoft Visual C++ */
 #elif defined _MSC_VER
@@ -67,7 +74,7 @@
 #endif
 
 /**
-  Generic compiler-dependent features.
+  Generic (compiler-independent) features.
 */
 #ifndef MY_ALIGNOF
 # ifdef __cplusplus
@@ -79,6 +86,10 @@
 # endif
 #endif
 
+#ifndef MY_ASSERT_UNREACHABLE
+# define MY_ASSERT_UNREACHABLE()  do { assert(0); } while (0)
+#endif
+
 /**
   C++ Type Traits
 */
diff --git a/sql/lock.cc b/sql/lock.cc
index 93d8b868688..e2216876635 100644
--- a/sql/lock.cc
+++ b/sql/lock.cc
@@ -693,7 +693,6 @@ TABLE_LIST *mysql_lock_have_duplicate(THD *thd, TABLE_LIST *needle,
                                       TABLE_LIST *haystack)
 {
   MYSQL_LOCK            *mylock;
-  TABLE                 **lock_tables;
   TABLE                 *table;
   TABLE                 *table2;
   THR_LOCK_DATA         **lock_locks;
@@ -722,12 +721,11 @@ TABLE_LIST *mysql_lock_have_duplicate(THD *thd, TABLE_LIST *needle,
   if (mylock->table_count < 2)
     goto end;
 
-  lock_locks=  mylock->locks;
-  lock_tables= mylock->table;
+  lock_locks= mylock->locks;
 
   /* Prepare table related variables that don't change in loop. */
   DBUG_ASSERT((table->lock_position < mylock->table_count) &&
-              (table == lock_tables[table->lock_position]));
+              (table == mylock->table[table->lock_position]));
   table_lock_data= lock_locks + table->lock_data_start;
   end_data= table_lock_data + table->lock_count;
 
@@ -741,7 +739,7 @@ TABLE_LIST *mysql_lock_have_duplicate(THD *thd, TABLE_LIST *needle,
 
     /* All tables in list must be in lock. */
     DBUG_ASSERT((table2->lock_position < mylock->table_count) &&
-                (table2 == lock_tables[table2->lock_position]));
+                (table2 == mylock->table[table2->lock_position]));
 
     for (lock_data2=  lock_locks + table2->lock_data_start,
            end_data2= lock_data2 + table2->lock_count;
diff --git a/sql/log.cc b/sql/log.cc
index 2d5b62a5b2b..38f4677f06f 100644
--- a/sql/log.cc
+++ b/sql/log.cc
@@ -1217,7 +1217,7 @@ void LOGGER::deactivate_log_handler(THD *thd, uint log_type)
     file_log= file_log_handler->get_mysql_log();
     break;
   default:
-    assert(0);                                  // Impossible
+    MY_ASSERT_UNREACHABLE();
   }
 
   if (!(*tmp_opt))
diff --git a/sql/set_var.cc b/sql/set_var.cc
index c5517da92f8..9fbce870dc4 100644
--- a/sql/set_var.cc
+++ b/sql/set_var.cc
@@ -2559,7 +2559,7 @@ bool update_sys_var_str_path(THD *thd, sys_var_str *var_str,
     file_log= logger.get_log_file_handler();
     break;
   default:
-    assert(0);                                  // Impossible
+    MY_ASSERT_UNREACHABLE();
   }
 
   if (!old_value)
diff --git a/sql/sql_acl.cc b/sql/sql_acl.cc
index ea002f59fe3..1733a0f74b4 100644
--- a/sql/sql_acl.cc
+++ b/sql/sql_acl.cc
@@ -5479,7 +5479,7 @@ static int handle_grant_struct(uint struct_no, bool drop,
       host= grant_name->host.hostname;
       break;
     default:
-      assert(0);
+      MY_ASSERT_UNREACHABLE();
     }
     if (! user)
       user= "";
diff --git a/sql/sql_help.cc b/sql/sql_help.cc
index 2818aa5082c..c21968cb86e 100644
--- a/sql/sql_help.cc
+++ b/sql/sql_help.cc
@@ -686,7 +686,7 @@ bool mysqld_help(THD *thd, const char *mask)
 
   if (count_topics == 0)
   {
-    int key_id;
+    int UNINIT_VAR(key_id);
     if (!(select=
           prepare_select_for_name(thd,mask,mlen,tables,tables[3].table,
                                   used_fields[help_keyword_name].field,
diff --git a/sql/sql_partition.cc b/sql/sql_partition.cc
index 76caa2b0c8d..702c3d99fda 100644
--- a/sql/sql_partition.cc
+++ b/sql/sql_partition.cc
@@ -6786,8 +6786,8 @@ int get_part_iter_for_interval_via_mapping(partition_info *part_info,
     }
   }
   else
-    assert(0);
-  
+    MY_ASSERT_UNREACHABLE();
+
   can_match_multiple_values= (flags || !min_value || !max_value ||
                               memcmp(min_value, max_value, field_len));
   if (can_match_multiple_values &&
diff --git a/sql/sql_union.cc b/sql/sql_union.cc
index 948ba1d9d9c..70598fbfcd4 100644
--- a/sql/sql_union.cc
+++ b/sql/sql_union.cc
@@ -173,7 +173,6 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
   SELECT_LEX *sl, *first_sl= first_select();
   select_result *tmp_result;
   bool is_union_select;
-  TABLE *empty_table= 0;
   DBUG_ENTER("st_select_lex_unit::prepare");
 
   describe= test(additional_options & SELECT_DESCRIBE);
@@ -275,14 +274,6 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
       types= first_sl->item_list;
     else if (sl == first_sl)
     {
-      /*
-        We need to create an empty table object. It is used
-        to create tmp_table fields in Item_type_holder.
-        The main reason of this is that we can't create
-        field object without table.
-      */
-      DBUG_ASSERT(!empty_table);
-      empty_table= (TABLE*) thd->calloc(sizeof(TABLE));
       types.empty();
       List_iterator_fast<Item> it(sl->item_list);
       Item *item_tmp;
diff --git a/storage/myisam/myisamchk.c b/storage/myisam/myisamchk.c
index 96ceb35b3d5..7f9776ca8d0 100644
--- a/storage/myisam/myisamchk.c
+++ b/storage/myisam/myisamchk.c
@@ -697,8 +697,7 @@ get_one_option(int optid,
   case OPT_STATS_METHOD:
   {
     int method;
-    enum_mi_stats_method method_conv;
-    LINT_INIT(method_conv);
+    enum_mi_stats_method UNINIT_VAR(method_conv);
     myisam_stats_method_str= argument;
     if ((method=find_type(argument, &myisam_stats_method_typelib, 2)) <= 0)
     {
diff --git a/storage/myisammrg/ha_myisammrg.cc b/storage/myisammrg/ha_myisammrg.cc
index 8e18924c5b8..4c8d45d1fe1 100644
--- a/storage/myisammrg/ha_myisammrg.cc
+++ b/storage/myisammrg/ha_myisammrg.cc
@@ -415,7 +415,7 @@ static MI_INFO *myisammrg_attach_children_callback(void *callback_param)
     my_errno= HA_ERR_WRONG_MRG_TABLE_DEF;
   }
   DBUG_PRINT("myrg", ("MyISAM handle: 0x%lx  my_errno: %d",
-                      my_errno ? NULL : (long) myisam, my_errno));
+                      my_errno ? 0L : (long) myisam, my_errno));
 
  err:
   DBUG_RETURN(my_errno ? NULL : myisam);