Re: [PATCH] help: make help_unknown_ref() NORETURN

From: René Scharfe <l.s.r@web.de>
Date: Aug 29, 2019, 20:08 UTC
Message-ID: <bde881b6-7c23-6f4e-5cb0-a793a5e4f5d7@web.de>
In-Reply-To: <CAN0heSp4bdJt4NKELOkvdpoygbkNZVn-96FrZnu9ymE5UNOSag@mail.gmail.com>

Am 29.08.19 um 21:40 schrieb Martin Ågren:

Show 15 quoted lines

> On Thu, 29 Aug 2019 at 21:15, René Scharfe <l.s.r@web.de> wrote:
>> diff --git a/help.h b/help.h
>> index b8780fbd0f..7a455beeb7 100644
>> --- a/help.h
>> +++ b/help.h
>> @@ -42,8 +42,8 @@ void list_commands(unsigned int colopts, struct cmdnames *main_cmds, struct cmdn
>>  /*
>>   * call this to die(), when it is suspected that the user mistyped a
>>   * ref to the command, to give suggested "correct" refs.
>>   */
>> -void help_unknown_ref(const char *ref, const char *cmd, const char *error);
>> +NORETURN void help_unknown_ref(const char *ref, const char *cmd, const char *error);
>
> Funny how this claims we'll call `die()`, when we'll actually call
> `exit(1)`.

Ah, I didn't even notice that.

> If we actually did call `die()`, I suppose the compiler
> should/could figure out by itself that this function, too, won't ever
> return.

The compiler can figure it out with exit(), too; system headers (at least for glibc, but it's probably common) assign it the noreturn attribute. But there is no way to transmit that information to callers across compilation units if not for the header file, right?

> I wonder whether the real bug here is that the implementation calls
> `exit(1)`, not `die()`. That is, the exit code is wrong (1 != 128) and
> we're missing out on the flexibility offered by `set_die_routine()`. If
> not that, then I'd say the documentation is buggy. Hm?

This inconsistency has been present since e56181060e ("help: add help_unknown_ref()", 2013-05-04). Using die() is going to be difficult due to the multi-line suggestions printed by the function.

René