Why would you use the ternary operator without assigning a value for the “true” condition (x = x ?: 1)

Question

In the Android open-source qemu code I ran across this line of code:

machine->max_cpus = machine->max_cpus ?: 1; /* Default to UP */

Answer 1

It's a GCC extension, and it gets more interesting and useful when the condition has side effects.

In this case, yes, I for one would agree it's obscure more than anything else.