Re: [PATCH 1/2] echo: pacify Oracle Studio 12.6

[Jim Meyering]

On Mon, Jun 1, 2020 at 4:45 PM Bob Proulx <bob@proulx.com> wrote:
> Paul Eggert wrote:
> > * src/echo.c (main): Don’t assign pointer to bool.
> > This is well-defined in C99, but is arguably bad style
> > and Oracle Studio 12.6 complains.
> ...
> > +  bool posixly_correct = !!getenv ("POSIXLY_CORRECT");
>
> Of course this is fine.  But because char *getenv() returns a pointer
> it just has this feeling of expressing frustration with the compiler
> seeing the !! there.  It feels like an obvious cast silencing a
> compiler warning.  Perhaps that is the intent? :-)
>
>   RETURN VALUE
>        The getenv() function returns a pointer to the value in the
>        environment, or NULL if there is no match.
>
> Just as a soft comment that isn't very strong if it were me I would
> use a comparison against a pointer which produced a boolean result and
> that boolean result used to assign to a bool.  It just feels to me
> like more of the types are more obvious this way.  And no cast of any
> type is either implicit or explicit.
>
>   bool posixly_correct = getenv ("POSIXLY_CORRECT") != NULL;

Hi Bob,

I had the same aversion to "!!", ... up until maybe a decade ago when
I realized we could view "!!" as a pointer-to-bool "operator".
It's an idiom that you have to use a few times before it starts to
become natural, then you won't want to go back.

Jim