Re: doc: Add appendix about Gnulib history

[Paul Eggert]

On 2024-05-03 17:14, Collin Funk wrote:
> Also about this comment in intprops-internal.h:
>
>      /* This include file assumes that signed types are two's complement without
>         padding bits; the above macros have undefined behavior otherwise.
>         If this is a problem for you, please let us know how to fix it for your 
> host.
>         This assumption is tested by the intprops-tests module.  */
>
> If you want to check this at compile time I think this should work:

Not quite, because it doesn't check for padding bits. Also, your code 
assumes that preprocessor arithmetic works the same as runtime 
arithmetic. Although C23 guarantees this (because it guarantees two's 
complement) I don't think C17 and earlier do. If memory serves, they 
even allow mixed-runtime systems, where arithmetic is sometimes ones' 
complement and sometimes two's. (Almost nobody cares about this 
theoretical possibility of course, which is why the Gnulib manual says 
not to worry about it.)