There seem to be a few missing operators, like ^^, &&=, and ->=.

A logical exclusive-or operator (hypothetically ``^^'') would be nice, but it couldn't possibly have short-circuiting behavior analogous to && and || Similarly, it's not clear how short-circuiting would apply to hypothetical assignment operators &&= and ||=. (It's also not clear how often &&= and ||= would actually be needed.)

Though p = p->next is an extremely common idiom for traversing a linked list, -> is not a binary arithmetic operator. A hypothetical ->= operator therefore wouldn't really fit the pattern of the other assignment operators.

You can write an exclusive-or macro in several ways:

#define XOR(a, b) ((a) && !(b) || !(a) && (b)) /* 1 */

#define XOR(a, b) (!!(a) ^ !!(b)) /* 2 */

#define XOR(a, b) (!!(a) != !!(b)) /* 3 */

#define XOR(a, b) (!(a) ^ !(b)) /* 4 */

#define XOR(a, b) (!(a) != !(b)) /* 5 */

#define XOR(a, b) ((a) ? !(b) : !!(b)) /* 6 */