Weird error on mysql_stmt_execute - c++

Question

I have a weird error when trying to execute mysql_stmt_execute.
The flow goes:
I get the list of the tables in my database I am connecting. (catalog, schema and name)
For every table I'm getting the list of foreign keys, fields and indexes.
Everything goes good until I hit the table named performance_schema.events_stages_summary_by_account_by_event_name.
I get the error: Identifier name "events_stages_summary_by_account_by_event_name" is too long. The weird thing is that the name is not an identifier - it is a parameter to the query and it is less than 64 characters which is the identifier limit.
Below is the relevant code:
std::wstring query3 = L"SELECT kcu.column_name, kcu.ordinal_position, kcu.referenced_table_schema, kcu.referenced_table_name, kcu.referenced_column_name, rc.update_rule, rc.delete_rule FROM information_schema.key_column_usage kcu, information_schema.referential_constraints rc WHERE kcu.constraint_name = rc.constraint_name AND kcu.table_catalog = ? AND kcu.table_schema = ? AND kcu.table_name = ?;";
char *catalog_name = row[0] ? row[0] : NULL;
char *schema_name = row[1] ? row[1] : NULL;
char *table_name = row[2] ? row[2] : NULL;
MYSQL_BIND params[3];
unsigned long str_length1, str_length2, str_length3;
str_length1 = strlen( catalog_name ) * 2;
str_length2 = strlen( schema_name ) * 2;
str_length3 = strlen( table_name ) * 2;
str_data1 = new char[str_length1], str_data2 = new char[str_length2], str_data3 = new char[str_length3];
memset( str_data1, '\0', str_length1 );
memset( str_data2, '\0', str_length2 );
memset( str_data3, '\0', str_length3 );
memset( params, 0, sizeof( params ) );
strncpy( str_data1, catalog_name, str_length1 );
strncpy( str_data2, schema_name, str_length2 );
strncpy( str_data3, table_name, str_length3 );
params[0].buffer_type = MYSQL_TYPE_STRING;
params[0].buffer = (char *) str_data1;
params[0].buffer_length = strlen( str_data1 );
params[0].is_null = 0;
params[0].length = &str_length1;
params[1].buffer_type = MYSQL_TYPE_STRING;
params[1].buffer = (char *) str_data2;
params[1].buffer_length = strlen( str_data2 );
params[1].is_null = 0;
params[1].length = &str_length2;
params[2].buffer_type = MYSQL_TYPE_STRING;
params[2].buffer = (char *) str_data3;
params[2].buffer_length = strlen( str_data3 );
params[2].is_null = 0;
params[2].length = &str_length3;
if( mysql_stmt_bind_param( res1, params ) )
{
std::wstring err = m_pimpl->m_myconv.from_bytes( mysql_stmt_error( res1 ) );
errorMsg.push_back( err );
result = 1;
break;
}
else
{
prepare_meta_result = mysql_stmt_result_metadata( res1 );
if( !prepare_meta_result )
{
std::wstring err = m_pimpl->m_myconv.from_bytes( mysql_stmt_error( res1 ) );
errorMsg.push_back( err );
result = 1;
break;
}
else
{
if( mysql_stmt_execute( res1 ) )
{
std::wstring err = m_pimpl->m_myconv.from_bytes( mysql_stmt_error( res1 ) );
errorMsg.push_back( err );
result = 1;
break;
}
Could someone please shed some light on the error? I can probably try to skip this table but I'd prefer not to.
[EDIT]
mysql --version
mysql ver 14.14 Distrib 5.6.35, for Linux (x86+64) using Editine wrapper
[/EDIT]

Answer 1

Edit:
Seems that the code is indeed OK and the strncpy is OK. I mistakenly read that the allocation was twice the length of the string but the length was still only one length of the string.
The reason why you see that error is because you are using a string which is not null terminated. This is caused by the fact that strncpy does not null-terminate the string if it exceeds the given limit and the limit you use is the actual length of the string:
memset( str_data1, '\0', str_length1 );
strncpy( str_data1, catalog_name, str_length1 );
params[0].buffer_length = strlen( str_data1 );
A better way to do this would be to use either snprintf(3) that does null terminate the string or by using the std::string constructor that takes a const char* and a length as parameters.