Uses of C comma operator [duplicate]

Answer 1

I've seen it used in macros where the macro is pretending to be a function and wants to return a value but needs to do some other work first. It's always ugly and often looks like a dangerous hack though.

Simplified example:

#define SomeMacro(A) ( DoWork(A), Permute(A) )

Here B=SomeMacro(A) "returns" the result of Permute(A) and assigns it to "B".