Re: Dynamic loading progress

[Paul Eggert]

Philipp Stephani wrote:
> This member will typically be used as follows:
>
> if (env->size >= sizeof *env) {
>    // good, object is at least as big as expected
> } else {
>    // Emacs is too old
> }


I'm leery of recommending this sort of checking.  In practice incompatible 
structure layout changes so often involve something more than merely extending a 
structure, that a size check is not worth the trouble; you really want a version 
check.  I might be persuaded that it's a good idea if I saw some code doing it 
effectively, but currently there is no such code in the Emacs sources (the 
module test function doesn't check sizes -- why not?).