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From: NRK <nrk@disroot.org>
To: Alejandro Colomar <alx@kernel.org>
Cc: Rich Felker <dalias@libc.org>,
	Guillem Jover <guillem@hadrons.org>,
	libc-alpha@sourceware.org, musl@lists.openwall.com,
	libbsd@lists.freedesktop.org,
		"Serge E. Hallyn" <serge@hallyn.com>,
	"Skyler Ferrante (RIT Student)" <sjf5462@rit.edu>,
	Iker Pedrosa <ipedrosa@redhat.com>,
	Christian Brauner <christian@brauner.io>
Subject: Re: [musl] Re: Tweaking the program name for <err.h> functions
Date: Sun, 10 Mar 2024 14:01:18 +0000	[thread overview]
Message-ID: <mr7ct4d47hn7bkhlj2ktcossu2q663pre6ggc5elkprveu4r3t@xowlfk5bccce> (raw)
In-Reply-To: <Ze2y-UNcfLNZypYu@debian>

>  or add locks; that is:
> 
> 	lock()
> 	fprintf("%s: ", __progname);
> 	vfprintf(...);
> 	unlock();
>
> [...]
>
> locking code is error-prone, I'd say.

These interfaces do not guarantee the output to be atomic. If you were
expecting it to be atomic then that's just *another* reason to roll it
yourself because a good ton of existing implementation doesn't lock.

https://github.com/bminor/musl/blob/master/src/legacy/err.c
https://github.com/freebsd/freebsd-src/blob/main/lib/libc/gen/err.c
https://github.com/openbsd/src/blob/master/lib/libc/gen/verr.c
https://cgit.freedesktop.org/libbsd/tree/src/err.c

musl doesn't, freebsd doesn't, openbsd doesn't, libbsd doesn't. Out of
the 5 implementations I checked, only glibc seems to lock.

> There's errc(3)

Which doesn't exist on musl, I don't think it exists on glibc either. So
you're back to "DIY or depend on libbsd" land if you use this function.

> Again, is there anything better in glibc or musl?
> Something that prefixes "$progname: " and appends the errno message?
> [...]
> And then add *c() for functions that return an errno-like code? And
> then add *x() variants for functions that don't use errno-like codes?

glibc has error(3), and program_invocation_name(3) to customize $progname.
Interface wise, I find it more pleasant than the err.h gang. Having an
explicit `errnum` argument serves all 3 usecases (no errno, errno,
errno-like return code) without having multiple functions with
x/y/z/c suffix.

(One issue I have with glibc's error() interface is that doing both
warning and fatal error through same function weakens static analyzers.
I'd split up the two and mark the fatal version with _Noreturn for
better warnings/static-analysis.)

But this function is even less portable (no musl or *BSD support last I
checked). So you're back to square one.

- NRK

  reply	other threads:[~2024-03-10 14:01 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-07 22:24 Alejandro Colomar
2024-03-08  0:30 ` Guillem Jover
2024-03-08  0:47   ` enh
2024-03-08  0:52   ` Alejandro Colomar
2024-03-09 15:02     ` [musl] " Rich Felker
2024-03-09 15:49       ` Alejandro Colomar
2024-03-09 18:35         ` Andreas Schwab
2024-03-09 18:46           ` Alejandro Colomar
2024-03-09 19:18             ` [musl] " Markus Wichmann
2024-03-09 19:25             ` Rich Felker
2024-03-09 21:44         ` Thorsten Glaser
2024-03-10  6:01         ` NRK
2024-03-10 13:17           ` Alejandro Colomar
2024-03-10 14:01             ` NRK [this message]
2024-03-10 19:39               ` Rich Felker
2024-03-10 22:25                 ` Alejandro Colomar
2024-03-10 23:22                 ` Thorsten Glaser
2024-03-10 23:44                   ` Rich Felker
2024-03-11  0:19                     ` Thorsten Glaser
2024-03-11  0:46                       ` Alejandro Colomar
2024-03-11 14:46                         ` Skyler Ferrante (RIT Student)
2024-03-11 15:09                           ` Andreas Schwab
2024-03-11 15:30                             ` Skyler Ferrante (RIT Student)
2024-03-11 18:23                               ` Florian Weimer
2024-03-11 18:48                                 ` Skyler Ferrante (RIT Student)
2024-03-11 19:05                                   ` enh
2024-03-11 19:44                                     ` Rich Felker
2024-03-11 20:35                                       ` enh
2024-03-11 19:47                               ` Rich Felker
2024-03-11 20:08                                 ` Skyler Ferrante (RIT Student)
2024-03-11 20:39                                   ` enh
2024-03-11 21:21                                 ` Laurent Bercot
2024-03-11 22:05                                 ` Thorsten Glaser
2024-03-12  0:18                                 ` Gabriel Ravier
2024-03-12  0:43                                   ` Rich Felker
2024-03-12  3:23                                     ` Gabriel Ravier
2024-03-12 14:44                                       ` Rich Felker
2024-03-12 13:54                                   ` Florian Weimer
2024-03-12 14:21                                     ` Zack Weinberg
2024-03-12 14:31                                       ` Florian Weimer
2024-03-12 14:42                                         ` Rich Felker
2024-03-12 19:25                                           ` Zack Weinberg
2024-03-12 21:19                                             ` Rich Felker
2024-03-13  8:28                                             ` Florian Weimer

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