Re: doc: Mention gnulib putenv module?

[Bruno Haible]

Hi Collin,

> > But maybe something could be clarified:
> >   - Does POSIX still not allow to remove an environment variable using
> >     this function?
> 
> I don't think that POSIX Issue 7 disallows it [1]. It appears that the
> behavior when '=' is not in the string is up for the implementation
> decide. This was reported in 2022 and the next revision will clarify
> that the environment variable can be removed or the function can fail
> with errno == EINVAL and a non-zero return value [2].
> 
> 
> >   - On which platforms does the native putenv() not allow to remove an
> >     environment variable using this function?
> 
> Good question. The POSIX report is well written so I won't retype it
> here [2]. :)

OK, I see.

The way to deal with it, that is most consistent with the rest of Gnulib,
is as follows:

  - Rename the 'putenv' module to 'putenv-gnu'.

  - Also change its description from:
    putenv() function: change or add an environment variable.
    to:
    putenv() function: change, add, or remove an environment variable.

  - Rename the 'putenv-tests' module to 'putenv-gnu-tests'.

  - Add a new 'putenv' module that is merely an indirection to 'putenv-gnu'
    (for backward compatibility, in order not to break coreutils, gcal, guile,
    octave, etc.). In the NEWS file mention
       2024-MM-DD  putenv          This module is renamed to 'putenv-gnu'.

Bruno