PQputCopyData dont signal error

Hello

I have a problem with PQputCopyData function. It doesn't signal some error.

while ((row = mysql_fetch_row(res)) != NULL)
{
snprintf(buffer, sizeof(buffer), "%s%s\n", row[0], row[1]);
copy_result = PQputCopyData(pconn, buffer, strlen(buffer));
printf(">>%s<<\n", PQerrorMessage(pconn));
printf("%d\n", copy_result);
if (copy_result != 1)
{
fprintf(stderr, "Copy to target table failed: %s",
PQerrorMessage(pconn));
EXIT;
}
}

it returns 1 for broken values too :(

Is necessary some special check?

Regards

Pavel Stehule