How to suppress the compiler warning on unused variable in C?

Question

For a peripheral requirement in an embedded system, I have to declare a variable to read a register, but won't use the value later. Hence, I get compiler warning about my unused variable naturally. How can I suppress the warning? I have 2 ways in mind:

1. using compiler directives, I hesitate because they are compiler-dependent

2. adding a dummy read from variable, like:

   volatile int var;
   
   var = peripheral_register;
   
   var = var;
   

Do you have a better idea?

Answer 1

If all you need to do is read the register (to clear some status flag for example), then you do not need a receiving variable at all just:

(void)peripheral_register ;

is sufficient assuming the register is itself is declared volatile so that it must be read.

Otherwise you could make your dummy var global with external linkage - that way the compiler cannot determine that it is not read elsewhere; but that's a far uglier solution.