Re: [PATCH 1/2] echo: pacify Oracle Studio 12.6
On Mon, Jun 1, 2020 at 4:45 PM Bob Proulx 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
Re: [PATCH 1/2] echo: pacify Oracle Studio 12.6
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;
But of course it's all a matter of style.
Bob
[PATCH 1/2] echo: pacify Oracle Studio 12.6
* 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.
---
src/echo.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/echo.c b/src/echo.c
index b5a6e966c..e7f3447ee 100644
--- a/src/echo.c
+++ b/src/echo.c
@@ -108,7 +108,7 @@ int
main (int argc, char **argv)
{
bool display_return = true;
- bool posixly_correct = getenv ("POSIXLY_CORRECT");
+ bool posixly_correct = !!getenv ("POSIXLY_CORRECT");
bool allow_options =
(! posixly_correct
|| (! DEFAULT_ECHO_TO_XPG && 1 < argc && STREQ (argv[1], "-n")));
--
2.17.1
