Differences between prefix-increment operator in C and C++

Question

I just read the C reference about prefix increment operator and realized that the result of prefix increment operator are not lvalue, but it's surprising that it is lvalue in C++. After that I read this answer which explaining why it's a lvalue, but I don't understand it:

(Line 3): ["] it appears that it is so you can take its address or assign to a reference. [."]

and an example follows:

int i;
extern void f (int* p);

f (&++i);   /* Would be illegal C, but C programmers
              havent missed this feature */
...

So what's the merit of allowing this? Is the only purpose of this that incrementing i in global region is illegal? If this is the only reason I would consider this be a remedy for a defect in C that cannot/hard to be resolved, or the program should probably be rewritten for the sake of readability, right?

btw I don't understand why lvalue is also called "locator value", I've read this - line 4 but locator is vague for me. What's a locator, is it a pointer something?

EDIT: For the sake of your precious time reading about wth is locator value, here is my homemade backronym:

• lvalue: location value, you know the location of it.
• rvalue: read value, you can only read the value.

don't blame me if anything gone wrong.

Answer 1

In C++, prefix ++ giving lvalue is actually very natural.

Because C++ has operator overloading. For most iterators of potentially complicated type, the prefix ++ returns the lvalue of the iterator itself.

Thus for generic programming, it would be inconvenient to make fundamental type a special case.

For example;

auto &iter = ++old_iter;

wouldn't work if prefix increment of pointer gives an rvalue.