__nonnull__ declarations

[Bruno Haible]

Hi Jim, all,

> >> I suggest you declare those functions with the "nonnull" attribute.
> 
> I was referring to the functions in progname.h:
> 
>   set_program_name
>   set_program_name_and_installdir

More generally, it could make sense to mark many functions in gnulib, from
"acl.h" to "xvasprintf.h", with __nonnull__ declaration annotations.

Arguments for doing it:
  - Allows GCC to produce its warning when passed a literal NULL value.
  - An added piece of documentation (but only when done completely,
    throughout gnulib).

Arguments against doing it:
  - People should expect to be able to pass NULL only when the documentation/
    specification says so. We should not encourage the expectation that NULL
    is valid everywhere.
  - It's a lot of work :-)

Opinions?

Bruno