What on earth use do you think that an
inline struct
would be? What difference would it make?
When you declare a function as
inline
you are asking teh compiler nicely to consider replacing calls to the function with the code directly:
inline int foo(int bar) { return bar + 1; }
...
x = foo(y);
becomes the same thing as writing this:
x = y + 1;
and it's used for performance reasons to try to avoid the stacking of parameters, the machine calls subroutine call, the unstacking, and the machine code return from subroutine - and it can make a big difference in a tight loop.
But a struct doesn't - and can't - contain any code. It allocates memory space, and that only when a variable is declared. So what possible use would trying to inline it be?
And that's what the compiler is telling you: "This is a pointless thing to do, so I'm going to ignore it". That's why it's a warning rather than an error: it has no effect on the eventual program, but it's something you should remove!