/*** Helper function to report ODBC errors */
void print_odbc_error(SQLSMALLINT handle_type, int critical) {
	SQLHANDLE hndl;          // Just to avoid passing the actual handle into this function.
	SQLCHAR sql_state[6];    // SQLSTATE is always 5 characters. google "msdn ODBC Error Codes" for code explanations
	SQLINTEGER native_error; // error code as reported by the driver. Driver specific, therefore ignored here.
	SQLCHAR message_text[2048];
	SQLSMALLINT message_length;

	// choose the appropriate handle
	switch(handle_type) {
	case SQL_HANDLE_ENV: hndl=henv; break;
	case SQL_HANDLE_DBC: hndl=hdbc; break;
	case SQL_HANDLE_STMT: hndl=hstmt; break;
	default: finish_process("Incorrect usage of print_odbc_error().", 2);
	}

	// Since any call to ODBC and/or database can return multiple messages, we have to iterate through them
	SQLSMALLINT record_number=1;
	while(TRUE) {
		retcode = SQLGetDiagRec(handle_type, hndl, record_number,
				sql_state, &native_error, message_text, sizeof(message_text), &message_length);
		if(retcode != SQL_SUCCESS) break;
		if( message_text[--message_length]=='\n') message_text[message_length]=0;
		sprintf(buf, "[SQLSTATE=%s] %s", sql_state, message_text);
		write_to_log(buf);
		record_number++;
	}

	if(critical) {
		odbc_cleanup();
		finish_process("Unrecoverable ODBC error", 2);
	}
}