Re: Fix C23 compiler warning

Peter Eisentraut <peter@eisentraut.org> writes:
> This no longer works because in C23, because an empty argument list is 
> now equivalent to (void), rather than an indeterminate one as before. 
> And so this results in an incompatible function pointer type and 
> compiler warnings.  (gcc and clang agree on this.)

> I think we can fix this easily with a few struct forward declarations, 
> preserving the goal of not including extra header files, like this:

Do the struct declarations themselves need comments?  Other
places do this like

struct PlannerInfo;                /* avoid including pathnodes.h here */

LGTM other than that nit.

            regards, tom lane