[jagorny]

Originally Posted by intel352

I've done a recursive search through all files from the stock 4.1.10 install, that function is defined only once. I then did a recursive search through all files from the 4.1.9 to 4.1.10 upgrade, I don't find that function mentioned at all, which means the function existed in 4.1.9 prior to the upgrade, and apparently hasn't been modified/added by the upgrade.

So quite strange the issue you're experiencing. I wonder if cart_process is getting included more than once for some reason.

In the upgrade from 4.1.9 to 4.1.10 look at the file include/cart_process.php.diff and you will see that a new function was added. This function was preventing my cart.php from displaying. Disabling the function restored operation.