From: Alejandro Colomar <alx.manpages@gmail.com>
To: Dan Cross <crossd@gmail.com>
Cc: tuhs@tuhs.org
Subject: [TUHS] printf (was: python)
Date: Fri, 4 Aug 2023 01:55:22 +0200 [thread overview]
Message-ID: <5dd50d2c-0049-31bf-8975-08ed899a9387@gmail.org> (raw)
In-Reply-To: <CAEoi9W4WRA5CL-ypRQ59A=iaZ+zXGO=-My55d0qkhVb-dSqZ2Q@mail.gmail.com>
Hi Dan,
On 2023-08-03 23:29, Dan Cross wrote:
> On Thu, Aug 3, 2023 at 2:05 PM Alejandro Colomar <alx.manpages@gmail.com> wrote:
>> On 2023-08-03 19:51, John Cowan wrote:
>>> On Thu, Aug 3, 2023 at 1:29 PM Alejandro Colomar <alx.manpages@gmail.com>
>>> wrote:
>>>
>>> But if speed is not a problem, I'd keep the good ol' syntax that
>>>
>>> everybody knows. No need to make everybody learn a "cool" new print
>>>> function, that probably won't be as tunable as printf(3) is.
>>>>
>>>>
>>> By that argument, there would be no C, only Algol 68 and PL/I, or subsets
>>> of them.
>>>
>>
>> I didn't claim that there's never a reason to invent new syntax. My claim
>> was rather that in this case, there isn't.
>>
>> - printf(3) is more powerful than any other existing formatting function
>> that I know of any language --I'm still curious of what's the equivalent
>> of "%+'0#8.5f" in other formatting functions--.
>
> One issue is that this isn't standard C: the `'` verb for grouping by
> thousands is an SUSv2 extension. I just checked the latest C23 draft,
> and unless I missed it, it doesn't appear to have made it in.
Being in POSIX.1 it's portable to most (all?) current systems. ISO C
is a baseline for an implementation. A quality implementation will
go beyond that standard (or will be rather useless). POSIX.1 is more
of a useful thing.
But yeah, we can remove that "'" to get the idea.
>
> But things like that are fairly straight-forward in many other
> languages. For example, in Go, the format string is nearly identical,
> modulo the `'`:
Yup; I like go in that sense.
[...]
>
>> - It is also reasonably fast (at least for such a highly-customizable
>> formatting function), and I'd like to see any system beat that while
>> keeping the customizability.
>
> At Google, a group of exceptionally talented engineers wrote a
> replacement in C++ for both type safety and because, bluntly, `printf`
> (actually `snprintf`) was too slow. I believe the overall mechanism
> made it into ABSL.
I think you mean absl::StrFormat(). It has printf(3)-like syntax, so
I can't say say much against it. I don't know the details of how they
achieved the claimed 2x ~ 3x performance compared to snprintf(3). I'm
curious to know if it's an inherent limitation of snprintf(3), or if
it's just that glibc is very unoptimized --which is true anyway, because
no-one has really maintained the printf(3) code in a long time--.
It's interesting, because then std::format() is not that miraculous
compared to snprintf(3).
>
>> - It is type-safe, with the right tools.
>
> No it's not, and it really can't be. True, there are linters that can
> try to match up types _if_ the format string is a constant and all the
> arguments are known at e.g. compile time, but C permits one to
> construct the format string at run time (or just select between a
> bunch of variants); the language gives you no tools to enforce type
> safety in a meaningful way once you do that.
Isn't a variable format string a security vulnerability? Where do you
need it?
Thanks,
Alex
next prev parent reply other threads:[~2023-08-03 23:55 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-30 18:22 [TUHS] Re: Cool talk on Unix and Sendmail history, by Eric Allman Norman Wilson
2023-07-30 21:43 ` Rob Pike
2023-07-30 23:34 ` George Michaelson
2023-07-30 23:59 ` Erik E. Fair
2023-07-31 0:26 ` Warner Losh
2023-07-31 22:57 ` Grant Taylor via TUHS
2023-07-31 23:05 ` Warner Losh
2023-08-01 2:45 ` Grant Taylor via TUHS
2023-08-01 1:51 ` Niklas Karlsson
2023-08-01 2:47 ` Grant Taylor via TUHS
2023-08-01 3:20 ` Theodore Ts'o
2023-07-31 0:41 ` segaloco via TUHS
2023-08-01 9:22 ` Marc Donner
2023-08-01 10:58 ` Erik E. Fair
2023-08-02 0:37 ` Dave Horsfall
2023-08-02 14:52 ` Ron Natalie
2023-08-02 21:14 ` Grant Taylor via TUHS
2023-08-02 22:20 ` segaloco via TUHS
2023-08-02 22:37 ` Warner Losh
2023-08-02 23:49 ` Rich Salz
2023-08-03 0:51 ` [TUHS] Re: python Larry McVoy
2023-08-03 1:20 ` George Michaelson
2023-08-03 2:53 ` Bakul Shah
2023-08-03 2:55 ` segaloco via TUHS
2023-08-03 3:24 ` George Michaelson
2023-08-03 3:32 ` Warner Losh
2023-08-03 3:55 ` Bakul Shah
2023-08-03 8:32 ` Rob Pike
2023-08-03 14:19 ` Bakul Shah
2023-08-03 14:56 ` Dan Halbert
2023-08-03 15:20 ` will.senn
2023-08-03 22:05 ` Dan Cross
2023-08-04 0:24 ` John Cowan
2023-08-04 15:17 ` Dan Cross
2023-08-05 4:44 ` Bakul Shah
2023-08-03 15:41 ` John Cowan
2023-08-03 2:07 ` Clem Cole
2023-08-03 2:21 ` Pete Wright via TUHS
2023-08-03 2:56 ` Warner Losh
2023-08-03 12:36 ` Mike Markowski
2023-08-03 13:29 ` Rob Pike
2023-08-03 15:24 ` emanuel stiebler
2023-08-03 15:39 ` Steffen Nurpmeso
2023-08-04 1:01 ` Larry McVoy
2023-08-04 1:28 ` segaloco via TUHS
2023-08-04 1:58 ` Adam Thornton
2023-08-04 15:04 ` Dan Cross
2023-08-04 15:10 ` Larry McVoy
2023-08-03 16:57 ` [TUHS] Re: [TULSA] " Phil Budne
2023-08-03 17:00 ` Rich Salz
2023-08-03 20:35 ` [TUHS] Split addressing (I/D) space (inspired by the death of the python... thread) Will Senn
2023-08-03 21:05 ` [TUHS] " Kenneth Goodwin
2023-08-03 21:10 ` Ronald Natalie
2023-08-03 21:16 ` Warner Losh
2023-08-03 21:24 ` Ronald Natalie
2023-08-03 22:34 ` Kenneth Goodwin
2023-08-03 21:05 ` Ronald Natalie
2023-08-03 21:44 ` Clem Cole
2023-08-03 22:08 ` Will Senn
2023-08-03 22:54 ` Clem Cole
2023-08-03 23:08 ` Dave Horsfall
2023-08-03 23:15 ` Clem Cole
2023-08-04 0:38 ` John Cowan
2023-08-03 17:29 ` [TUHS] Re: [TULSA] Re: python Alejandro Colomar
2023-08-03 17:51 ` John Cowan
2023-08-03 18:05 ` Alejandro Colomar
2023-08-03 21:29 ` Dan Cross
2023-08-03 23:55 ` Alejandro Colomar [this message]
2023-08-04 16:06 ` [TUHS] Re: printf (was: python) Dan Cross
2023-08-04 16:57 ` Alejandro Colomar
2023-08-04 21:16 ` Dan Cross
2023-08-03 21:02 ` [TUHS] Re: [TULSA] Re: python Steffen Nurpmeso
2023-08-03 23:47 ` Larry McVoy
2023-08-03 23:54 ` Will Senn
2023-08-04 19:20 ` [TUHS] " Ed Bradford
2023-08-04 19:47 ` Larry McVoy
2023-08-05 5:40 ` Ed Bradford
2023-08-02 23:33 ` [TUHS] Re: Cool talk on Unix and Sendmail history, by Eric Allman Dave Horsfall
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