Bug#14640599 MEMORY LEAK WHEN EXECUTING STORED ROUTINE EXCEPTION HANDLER

When a SP handler is activated, memory is allocated to hold the
MESSAGE_TEXT for the condition that caused the activation.

The problem was that this memory was allocated on the MEM_ROOT belonging
to the stored program. Since this MEM_ROOT is not freed until the
stored program ends, a stored program that causes lots of handler
activations can start using lots of memory. In 5.1 and earlier the
problem did not exist as no MESSAGE_TEXT was allocated if a condition
was raised with a handler present. However, this behavior lead to
a number of other issues such as Bug#23032.

This patch fixes the problem by allocating enough memory for the
necessary MESSAGE_TEXTs in the SP MEM_ROOT when the SP starts and
then re-using this memory each time a handler is activated.
      
This is the 5.5 version of the patch.

sql/sp_rcontext.cc

@@ -67,19 +67,15 @@ sp_rcontext::~sp_rcontext()
 bool sp_rcontext::init(THD *thd)
 {
   uint handler_count= m_root_parsing_ctx->max_handler_index();
-  uint i;
 
   in_sub_stmt= thd->in_sub_stmt;
 
   if (init_var_table(thd) || init_var_items())
     return TRUE;
 
-  if (!(m_raised_conditions= new (thd->mem_root) MYSQL_ERROR[handler_count]))
+  if (!(m_raised_conditions= new (thd->mem_root) Sql_condition_info[handler_count]))
     return TRUE;
 
-  for (i= 0; i<handler_count; i++)
-    m_raised_conditions[i].init(thd->mem_root);
-
   return
     !(m_handler=
       (sp_handler_t*)thd->alloc(handler_count * sizeof(sp_handler_t))) ||
@@ -446,13 +442,12 @@ sp_rcontext::exit_handler()
   DBUG_VOID_RETURN;
 }
 
-MYSQL_ERROR*
-sp_rcontext::raised_condition() const
+Sql_condition_info* sp_rcontext::raised_condition() const
 {
   if (m_ihsp > 0)
   {
     uint hindex= m_in_handler[m_ihsp - 1].index;
-    MYSQL_ERROR *raised= & m_raised_conditions[hindex];
+    Sql_condition_info *raised= & m_raised_conditions[hindex];
     return raised;
   }
 

sql/sp_rcontext.h

@@ -58,6 +58,46 @@ typedef struct
   uint index;
 } sp_active_handler_t;
 
+
+class Sql_condition_info : public Sql_alloc
+{
+public:
+  /** SQL error code. */
+  uint m_sql_errno;
+
+  /** Error level. */
+  MYSQL_ERROR::enum_warning_level m_level;
+
+  /** SQLSTATE. */
+  char m_sql_state[SQLSTATE_LENGTH + 1];
+
+  /** Text message. */
+  char m_message[MYSQL_ERRMSG_SIZE];
+
+  void set(uint sql_errno, const char* sqlstate,
+           MYSQL_ERROR::enum_warning_level level,
+           const char* msg)
+  {
+    m_sql_errno= sql_errno;
+    m_level= level;
+
+    memcpy(m_sql_state, sqlstate, SQLSTATE_LENGTH);
+    m_sql_state[SQLSTATE_LENGTH]= '\0';
+
+    strncpy(m_message, msg, MYSQL_ERRMSG_SIZE);
+  }
+
+  void clear()
+  {
+    m_sql_errno= 0;
+    m_level= MYSQL_ERROR::WARN_LEVEL_ERROR;
+
+    m_sql_state[0]= '\0';
+    m_message[0]= '\0';
+  }
+};
+
+
 /*
   This class is a runtime context of a Stored Routine. It is used in an
   execution and is intended to contain all dynamic objects (i.e.  objects, which
@@ -146,8 +186,7 @@ class sp_rcontext : public Sql_alloc
                MYSQL_ERROR::enum_warning_level level,
                const char *msg);
 
-  MYSQL_ERROR *
-  raised_condition() const;
+  Sql_condition_info *raised_condition() const;
 
   void
   push_hstack(uint h);
@@ -232,7 +271,7 @@ private:
     SQL conditions caught by each handler.
     This is an array indexed by handler index.
   */
-  MYSQL_ERROR *m_raised_conditions;
+  Sql_condition_info *m_raised_conditions;
 
   uint m_hcount;                // Stack pointer for m_handler
   uint *m_hstack;               // Return stack for continue handlers

sql/sql_signal.cc

@@ -478,7 +478,7 @@ bool Signal_statement::execute(THD *thd)
 
 bool Resignal_statement::execute(THD *thd)
 {
-  MYSQL_ERROR *signaled;
+  Sql_condition_info *signaled;
   int result= TRUE;
 
   DBUG_ENTER("Resignal_statement::execute");
@@ -491,15 +491,21 @@ bool Resignal_statement::execute(THD *thd)
     DBUG_RETURN(result);
   }
 
+  MYSQL_ERROR signaled_err(thd->mem_root);
+  signaled_err.set(signaled->m_sql_errno,
+                   signaled->m_sql_state,
+                   signaled->m_level,
+                   signaled->m_message);
+
   if (m_cond == NULL)
   {
     /* RESIGNAL without signal_value */
-    result= raise_condition(thd, signaled);
+    result= raise_condition(thd, &signaled_err);
     DBUG_RETURN(result);
   }
 
   /* RESIGNAL with signal_value */
-  result= raise_condition(thd, signaled);
+  result= raise_condition(thd, &signaled_err);
 
   DBUG_RETURN(result);
 }