Improving code readability through temporary variables

We don't always have the luxury of using library interfaces that are sensibly designed and enforce readability self-explanatory (see this presentation). A fictional function may look like this:

extern void foo(struct foo *f, 
                Bool check_device, 
                int max_devices, 
                Bool emulate);

But a calls often end up like this:

foo(mystruct, TRUE, 0, FALSE);

Or, even worse, the function call could be:

foo(mystruct, !dev->invalid, 0, list_is_first_entry(dev->list));

The above is virtually unreadable and to understand it one needs to look at the function definition and the caller at the same time. The simple use of a temporary variable can do wonders here:

Bool check_device = !dev->invalid;
Bool emulate_pointer = list_is_first_entry(dev->list));

foo(mystruct, check_device, 0, emulate_pointer);

It adds a few lines of code (though I suspect the compiler will mostly reduce the output anyway) but it improves readability. Especially in the cases where the source field name is vastly different to the implied effect. In the second example, it's immediately obvious that pointer emulation should happen for the first entry.