Re: Dynamic loading progress

[Paul Eggert]

Philipp Stephani wrote:
> I honestly can't think of a situation where version checking would work but
> size checking wouldn't.

For example, a structure contains an off_t value, and time_t grows from 32 to 
64-bits.  The designer knew this might be a problem because of Y2038 issues, and 
so created padding for the time_t to grow into.

Another example: suppose we change ptrdiff_t back to int.

Another example: suppose we want the same module to work in both narrow and wide 
int Emacs, so we allocate storage for wide integers even though half of them are 
not used in narrow platforms.

What you're saying, if I understand it, is that we promise that we'll never make 
any changes like that.  This sounds overly constraining, at least for now. 
While the interface is experimental we'll retain the freedom to make arbitrary 
changes to it. When it settles down we can think about promises about never ever 
making changes in the future. In the meantime the size field is experimental and 
maybe we'll think of uses for it other than sizes.