From: Rasmus Villemoes <linux-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
To: Andy Shevchenko
<andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Cc: Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Trond Myklebust
<trond.myklebust-7I+n7zu2hftEKMMhf/gKZA@public.gmane.org>,
"J. Bruce Fields"
<bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>,
"David S. Miller" <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH v2 3/3] lib/string_helpers.c: Change semantics of string_escape_mem
Date: Sat, 31 Jan 2015 00:39:22 +0100 [thread overview]
Message-ID: <87pp9vhm8l.fsf@rasmusvillemoes.dk> (raw)
In-Reply-To: <1422613655.31903.351.camel-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> (Andy Shevchenko's message of "Fri, 30 Jan 2015 12:27:35 +0200")
On Fri, Jan 30 2015, Andy Shevchenko <andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> wrote:
> On Thu, 2015-01-29 at 15:29 +0100, Rasmus Villemoes wrote:
>> On Thu, Jan 29 2015, Andy Shevchenko <andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> wrote:
>>
>> >> *
>> >> * Return:
>> >> - * The amount of the characters processed to the destination buffer, or
>> >> - * %-ENOMEM if the size of buffer is not enough to put an escaped character is
>> >> - * returned.
>> >> - *
>> >> - * Even in the case of error @dst pointer will be updated to point to the byte
>> >> - * after the last processed character.
>> >> + * The total size of the escaped output that would be generated for
>> >> + * the given input and flags. To check whether the output was
>> >> + * truncated, compare the return value to osz. There is room left in
>> >> + * dst for a '\0' terminator if and only if ret < osz.
>> >> */
>> >> -int string_escape_mem(const char *src, size_t isz, char **dst, size_t osz,
>> >> - unsigned int flags, const char *esc)
>> >> +size_t string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
>> >> + unsigned int flags, const char *esc)
>> >
>> > I prefer to leave the prototype the same. int for return is okay. dst
>> > should be updated accordingly.
>>
>> Please explain exactly what you think the return value should be, and
>> what *dst should be set to.
>
> Return value like you proposed, *dst is incremented by it.
The more I think about it, the less I like having dst being char**.
(1) It is unlike most other functions taking buffer+size arguments.
(2) It is inconvenient. Callers doing
char escaped[SOME_SIZE];
or
char *escaped = kmalloc(likely_big_enough);
can't just pass &escaped; they would need to use an extra dummy variable.
(3) With the return value telling the size of the would-be generated
output, it is redundant.
In fact, I dislike it so much that I'm not going to sign off on a patch
where dst is still char**.
>> > Could it be a part of nomem test still?
>>
>> What nomem test? string_escape_mem with snprintf-like semantics cannot
>> return an error; that has to be checked by the caller.
>
> Make this code a separate test, which actually still nomem, since you
> have not enough memory in the destination buffer. What the problem to
> check for proper return value and the last couple of characters written
> to the destination buffer?
Sure, it could go into a separate helper. Anyway, the semantics of
string_escape_mem needs to be decided before it makes sense to update
the tests.
> When your series will be ready (and actually I recommend to push first
> patch apart from the rest since it's not related)
I agree on that part. Andrew, could you take 1/3
(http://thread.gmane.org/gmane.linux.kernel/1876841/focus=348404), and
then we'll see when the %pE case gets sorted out.
Rasmus
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next prev parent reply other threads:[~2015-01-30 23:39 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-28 13:25 [PATCH 0/2] Two printf fixes Rasmus Villemoes
2015-01-28 13:25 ` [PATCH 2/2] string_helpers: Change semantics of string_escape_mem Rasmus Villemoes
2015-01-28 15:05 ` Andy Shevchenko
2015-01-29 10:03 ` [PATCH v2 0/3] Two printf fixes Rasmus Villemoes
2015-01-29 10:03 ` [PATCH v2 3/3] lib/string_helpers.c: Change semantics of string_escape_mem Rasmus Villemoes
2015-01-29 13:29 ` Andy Shevchenko
2015-01-29 14:29 ` Rasmus Villemoes
2015-01-30 10:27 ` Andy Shevchenko
[not found] ` <1422613655.31903.351.camel-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2015-01-30 23:39 ` Rasmus Villemoes [this message]
2015-02-02 10:56 ` Andy Shevchenko
[not found] ` <1422525801-26560-1-git-send-email-linux-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-02-09 23:44 ` [PATCH v3 0/3] Two printf fixes Rasmus Villemoes
[not found] ` <1423525491-12613-1-git-send-email-linux-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-02-09 23:44 ` [PATCH v3 3/3] lib/string_helpers.c: Change semantics of string_escape_mem Rasmus Villemoes
[not found] ` <1423525491-12613-4-git-send-email-linux-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-02-10 12:32 ` Andy Shevchenko
2015-02-10 13:02 ` Rasmus Villemoes
[not found] ` <87386dj4x0.fsf-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-02-10 14:22 ` Andy Shevchenko
2015-02-21 1:35 ` Rasmus Villemoes
[not found] ` <87oaoo59n2.fsf-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-02-23 12:50 ` Andy Shevchenko
[not found] ` <1424695820.14897.10.camel-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2015-02-23 22:55 ` Rasmus Villemoes
[not found] ` <87k2z86xvs.fsf-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-03-02 12:37 ` Andy Shevchenko
2015-03-02 23:03 ` Rasmus Villemoes
[not found] ` <87a8zvovcj.fsf-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-03-03 10:26 ` Andy Shevchenko
2015-03-03 23:20 ` [PATCH v4 0/3] Two printf fixes Rasmus Villemoes
2015-03-03 23:20 ` [PATCH v4 3/3] lib/string_helpers.c: Change semantics of string_escape_mem Rasmus Villemoes
[not found] ` <1425424836-17947-4-git-send-email-linux-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-03-04 11:49 ` Andy Shevchenko
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