Fix -Wstringop-truncation

For the Sphinx storage engine, this is a functional change (bug fix):
we will ensure that the message buffer is always NUL-terminated.

storage/perfschema/pfs_instr.cc

@@ -1265,7 +1265,6 @@ find_or_create_file(PFS_thread *thread, PFS_file_class *klass,
   char dirbuffer[FN_REFLEN];
   size_t dirlen;
   const char *normalized_filename;
-  int normalized_length;
 
   dirlen= dirname_length(safe_filename);
   if (dirlen == 0)
@@ -1296,7 +1295,7 @@ find_or_create_file(PFS_thread *thread, PFS_file_class *klass,
   *buf_end= '\0';
 
   normalized_filename= buffer;
-  normalized_length= strlen(normalized_filename);
+  size_t normalized_length= strlen(normalized_filename);
 
   PFS_file **entry;
   uint retry_count= 0;
@@ -1345,7 +1344,7 @@ find_or_create_file(PFS_thread *thread, PFS_file_class *klass,
         pfs->m_class= klass;
         pfs->m_enabled= klass->m_enabled && flag_global_instrumentation;
         pfs->m_timed= klass->m_timed;
-        strncpy(pfs->m_filename, normalized_filename, normalized_length);
+        strncpy(pfs->m_filename, normalized_filename, normalized_length + 1);
         pfs->m_filename[normalized_length]= '\0';
         pfs->m_filename_length= normalized_length;
         pfs->m_file_stat.m_open_count= 1;

storage/sphinx/ha_sphinx.cc

@@ -2291,7 +2291,8 @@ int ha_sphinx::HandleMysqlError ( MYSQL * pConn, int iErrCode )
 	CSphSEThreadTable * pTable = GetTls ();
 	if ( pTable )
 	{
-		strncpy ( pTable->m_tStats.m_sLastMessage, mysql_error ( pConn ), sizeof ( pTable->m_tStats.m_sLastMessage ) );
+		strncpy ( pTable->m_tStats.m_sLastMessage, mysql_error ( pConn ), sizeof pTable->m_tStats.m_sLastMessage - 1 );
+		pTable->m_tStats.m_sLastMessage[sizeof pTable->m_tStats.m_sLastMessage - 1] = '\0';
 		pTable->m_tStats.m_bLastError = true;
 	}
 
@@ -2558,7 +2559,8 @@ bool ha_sphinx::UnpackSchema ()
 		CSphSEThreadTable * pTable = GetTls ();
 		if ( pTable )
 		{
-			strncpy ( pTable->m_tStats.m_sLastMessage, sMessage, sizeof(pTable->m_tStats.m_sLastMessage) );
+			strncpy ( pTable->m_tStats.m_sLastMessage, sMessage, sizeof pTable->m_tStats.m_sLastMessage - 1 );
+			pTable->m_tStats.m_sLastMessage[sizeof pTable->m_tStats.m_sLastMessage - 1] = '\0';
 			pTable->m_tStats.m_bLastError = ( uStatus==SEARCHD_ERROR );
 		}
 
@@ -2982,7 +2984,8 @@ int ha_sphinx::index_read ( byte * buf, const byte * key, uint key_len, enum ha_
 			SPH_RET ( HA_ERR_END_OF_FILE );
 		}
 
-		strncpy ( pTable->m_tStats.m_sLastMessage, sMessage, sizeof(pTable->m_tStats.m_sLastMessage) );
+		strncpy ( pTable->m_tStats.m_sLastMessage, sMessage, sizeof pTable->m_tStats.m_sLastMessage - 1 );
+		pTable->m_tStats.m_sLastMessage[sizeof pTable->m_tStats.m_sLastMessage - 1] = '\0';
 		SafeDeleteArray ( sMessage );
 
 		if ( uRespStatus!=SEARCHD_WARNING )