Non-void function used in void context?

Question

I am using SystemVerilog. My code is:

function write_pixel_data(datastr ds);
 /* some stuff here... but no return */
endfunction

then i am calling my function like:

write_pixel_data(someval);

And i get the vcs warning:

Warning-[SV-NFIVC] Non-void function used in void context.

But i am not returning anything, i know i can cast the function call to void to get rid of the warning. But why it gives this warning??!!

Thanks.

Answer 1

If you haven't declared the function as void and you call it without assigning the return value to anything, you'll see this error. Simple fix:

function void write_pixel_data(datastr ds);
 /* some stuff here... but no return */
endfunction

Careful though, you can't do anything that 'takes time' in a function. You'll need a task for that.

Answer 2

A function declared with an implicit type returns logic. You must explicitly declare the return type to be void if that is your intention.