In ha_delete_table, use a standard mechanism to intercept the error message

and convert it to a warning instead of direct manipulation with the
thread error stack.
Fix a bug in handler::print_erorr when a garbled message was
printed for HA_ERR_NO_SUCH_TABLE.
This is a pre-requisite patch for the fix for Bug#12713 Error in a stored
function called from a SELECT doesn't cause ROLLBACK of statem


sql/handler.cc:
  Use a standard mechanism to intercept the error message, instead
  of direct manipulation with thread error stack. 
  Fix a bug when for HA_ERR_NO_SUCH_TABLE handler::print_error() would
  print a garbled message.
sql/log.cc:
  Extend internal error handler interface to carry the message text.
sql/mysqld.cc:
  Extend internal error handler interface to carry the message text.
sql/sql_base.cc:
  Extend internal error handler interface to carry the message text.
sql/sql_class.cc:
  Extend internal error handler interface to carry the message text.
sql/sql_class.h:
  Extend internal error handler interface to carry the message text.
sql/sql_error.cc:
  Extend internal error handler interface to carry the message text.

sql/handler.cc

@@ -1414,6 +1414,36 @@ static const char *check_lowercase_names(handler *file, const char *path,
 }
 
 
+/**
+  An interceptor to hijack the text of the error message without
+  setting an error in the thread. We need the text to present it
+  in the form of a warning to the user.
+*/
+
+struct Ha_delete_table_error_handler: public Internal_error_handler
+{
+public:
+  virtual bool handle_error(uint sql_errno,
+                            const char *message,
+                            MYSQL_ERROR::enum_warning_level level,
+                            THD *thd);
+  char buff[MYSQL_ERRMSG_SIZE];
+};
+
+
+bool
+Ha_delete_table_error_handler::
+handle_error(uint sql_errno,
+             const char *message,
+             MYSQL_ERROR::enum_warning_level level,
+             THD *thd)
+{
+  /* Grab the error message */
+  strmake(buff, message, sizeof(buff)-1);
+  return TRUE;
+}
+
+
 /** @brief
   This should return ENOENT if the file doesn't exists.
   The .frm file will be deleted only if we return 0 or ENOENT
@@ -1442,23 +1472,11 @@ int ha_delete_table(THD *thd, handlerton *table_type, const char *path,
   {
     /*
       Because file->print_error() use my_error() to generate the error message
-      we must store the error state in thd, reset it and restore it to
-      be able to get hold of the error message.
-      (We should in the future either rewrite handler::print_error() or make
-      a nice method of this.
+      we use an internal error handler to intercept it and store the text
+      in a temporary buffer. Later the message will be presented to user
+      as a warning.
     */
-    bool is_slave_error= thd->is_slave_error;
-    sp_rcontext *spcont= thd->spcont;
-    SELECT_LEX *current_select= thd->lex->current_select;
-    char buff[sizeof(thd->net.last_error)];
-    char new_error[sizeof(thd->net.last_error)];
-    int last_errno= thd->net.last_errno;
-
-    strmake(buff, thd->net.last_error, sizeof(buff)-1);
-    thd->is_slave_error= 0;
-    thd->spcont= NULL;
-    thd->lex->current_select= 0;
-    thd->net.last_error[0]= 0;
+    Ha_delete_table_error_handler ha_delete_table_error_handler;
 
     /* Fill up strucutures that print_error may need */
     dummy_share.path.str= (char*) path;
@@ -1471,16 +1489,18 @@ int ha_delete_table(THD *thd, handlerton *table_type, const char *path,
 
     file->table_share= &dummy_share;
     file->table= &dummy_table;
+
+    thd->push_internal_handler(&ha_delete_table_error_handler);
     file->print_error(error, 0);
-    strmake(new_error, thd->net.last_error, sizeof(buff)-1);
 
-    /* restore thd */
-    thd->is_slave_error= is_slave_error;
-    thd->spcont= spcont;
-    thd->lex->current_select= current_select;
-    thd->net.last_errno= last_errno;
-    strmake(thd->net.last_error, buff, sizeof(buff)-1);
-    push_warning(thd, MYSQL_ERROR::WARN_LEVEL_ERROR, error, new_error);
+    thd->pop_internal_handler();
+
+    /*
+      XXX: should we convert *all* errors to warnings here?
+      What if the error is fatal?
+    */
+    push_warning(thd, MYSQL_ERROR::WARN_LEVEL_ERROR, error,
+                ha_delete_table_error_handler.buff);
   }
   delete file;
   DBUG_RETURN(error);
@@ -2203,7 +2223,7 @@ void handler::print_error(int error, myf errflag)
   case HA_ERR_NO_SUCH_TABLE:
     my_error(ER_NO_SUCH_TABLE, MYF(0), table_share->db.str,
              table_share->table_name.str);
-    break;
+    DBUG_VOID_RETURN;
   case HA_ERR_RBR_LOGGING_FAILED:
     textno= ER_BINLOG_ROW_LOGGING_FAILED;
     break;

sql/log.cc

@@ -72,13 +72,14 @@ class Silence_log_table_errors : public Internal_error_handler
 
   virtual ~Silence_log_table_errors() {}
 
-  virtual bool handle_error(uint sql_errno,
+  virtual bool handle_error(uint sql_errno, const char *message,
                             MYSQL_ERROR::enum_warning_level level,
                             THD *thd);
 };
 
 bool
 Silence_log_table_errors::handle_error(uint /* sql_errno */,
+                                       const char * /* message */,
                                        MYSQL_ERROR::enum_warning_level /* level */,
                                        THD * /* thd */)
 {

sql/mysqld.cc

@@ -2583,7 +2583,7 @@ int my_message_sql(uint error, const char *str, myf MyFlags)
       TODO: There are two exceptions mechanism (THD and sp_rcontext),
       this could be improved by having a common stack of handlers.
     */
-    if (thd->handle_error(error,
+    if (thd->handle_error(error, str,
                           MYSQL_ERROR::WARN_LEVEL_ERROR))
       DBUG_RETURN(0);
 

sql/sql_base.cc

@@ -44,7 +44,7 @@ class Prelock_error_handler : public Internal_error_handler
 
   virtual ~Prelock_error_handler() {}
 
-  virtual bool handle_error(uint sql_errno,
+  virtual bool handle_error(uint sql_errno, const char *message,
                             MYSQL_ERROR::enum_warning_level level,
                             THD *thd);
 
@@ -58,6 +58,7 @@ class Prelock_error_handler : public Internal_error_handler
 
 bool
 Prelock_error_handler::handle_error(uint sql_errno,
+                                    const char * /* message */,
                                     MYSQL_ERROR::enum_warning_level /* level */,
                                     THD * /* thd */)
 {

sql/sql_class.cc

@@ -498,12 +498,12 @@ void THD::push_internal_handler(Internal_error_handler *handler)
 }
 
 
-bool THD::handle_error(uint sql_errno,
+bool THD::handle_error(uint sql_errno, const char *message,
                        MYSQL_ERROR::enum_warning_level level)
 {
   if (m_internal_handler)
   {
-    return m_internal_handler->handle_error(sql_errno, level, this);
+    return m_internal_handler->handle_error(sql_errno, message, level, this);
   }
 
   return FALSE;                                 // 'FALSE', as per coding style

sql/sql_class.h

@@ -969,6 +969,7 @@ class Internal_error_handler
     @return true if the error is handled
   */
   virtual bool handle_error(uint sql_errno,
+                            const char *message,
                             MYSQL_ERROR::enum_warning_level level,
                             THD *thd) = 0;
 };
@@ -1923,7 +1924,7 @@ class THD :public Statement,
     @param level the error level
     @return true if the error is handled
   */
-  virtual bool handle_error(uint sql_errno,
+  virtual bool handle_error(uint sql_errno, const char *message,
                             MYSQL_ERROR::enum_warning_level level);
 
   /**

sql/sql_error.cc

@@ -137,7 +137,7 @@ MYSQL_ERROR *push_warning(THD *thd, MYSQL_ERROR::enum_warning_level level,
     level= MYSQL_ERROR::WARN_LEVEL_ERROR;
   }
 
-  if (thd->handle_error(code, level))
+  if (thd->handle_error(code, msg, level))
     DBUG_RETURN(NULL);
 
   if (thd->spcont &&