[bug#59994] [PATCH] tests: Don't try to prevent flex to include unistd.h

[Zack Weinberg]

On 2022-12-12 2:07 AM, Frederic Berat wrote:
> This patch is mainly a proposal. While the macro can simply be removed
> as explained below, another possibility it to add a flex option
> "--never-interactive" to prevent flex to make use of "isatty".
>
> This is related to an effort to prepare Automake for future GCC/Clang
> versions which set c99 as default standard to be used.
>
> Future version of flex make the "NO_UNISTD" flag a no-op, and include
> unistd.h by default.
>
> In current version of flex, not having this header leads to implicit
> function declarations that are not compatible with c99 standard.
>
> On top of that, while flex dedicated test were having this macro set,
> the yacc ones didn't have it despise their use of Flex. Thus, if this
> macro was ever useful, it looks like nobody actually cared.

I'm guessing that the idea here was to avoid using unistd.h on platforms 
that don't supply that header at all.  I suggest that we should apply 
your patch *and* consistently test flex with "--never-interactive".

zw