Re: as for Calc and the math library

[Suhail Singh <suhailsingh247@gmail.com>]

Eli Zaretskii <eliz@gnu.org> writes:

>> On the topic of what would be acceptable for an FFI, wouldn't something
>> akin to what's done for modules be sufficient ?  I.e., have the users of
>> the interface explicitly state that they are compliant.
>> 
>> It would scale better than an allow-list.  IIUC, Arthur mentioned this
>> in another thread.  If this wouldn't be sufficient for an FFI, could you
>> please elaborate on why that's the case ?
>
> What exactly are you suggesting?  IOW, please describe what you have
> in mind in more detail, because I don't think I understand it.

Specifically, modify the `define-ffi-library' macro that emacs-ffi
provides.

Presently, it takes two arguments: a SYMBOL and a NAME.  I am proposing
that it be updated to take three arguments: a SYMBOL, a NAME and a
GPL-COMPATIBLE-P token.  A value of `t' would be necessary for creating
a reference to the library.

If the value of `t' would be insufficient for Emacs' standards for
encouraging GPL compliance (in case it's considered "not explicit
enough"), the third argument could instead be something like
GPL-COMPATIBILITY where the value of 'library-is-GPL-compatible would be
necessary to be able to create a reference to the library.

A further variant/extension of the above proposal is also possible.
This extension modifies both `define-ffi-library' as well as
`define-ffi-function'.  When `define-ffi-library' gets an acceptable
claim of GPL compatibility, it attaches a property (which acts as a
witness for observing the claim of GPL compatibility) to the library
symbol.  The presence of said property is then checked by
`define-ffi-function'.  If the property is missing,
`define-ffi-function' complains.

-- 
Suhail