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Groups > comp.lang.c > #107832
| From | Ben Bacarisse <ben.usenet@bsb.me.uk> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: How to fix: [-Wformat-nonliteral] |
| Date | 2017-04-07 19:35 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <87h920ukud.fsf@bsb.me.uk> (permalink) |
| References | <oc7g6c$lpq$1@dont-email.me> <oc7nm7$d6i$1@dont-email.me> <87mvbsv0tq.fsf@bsb.me.uk> <oc85gk$s8g$1@dont-email.me> |
David Brown <david.brown@hesbynett.no> writes:
> On 07/04/17 14:50, Ben Bacarisse wrote:
>> David Brown <david.brown@hesbynett.no> writes:
>> <snip>
>>> #define my_errPrintfBuffLen 256
>>> #define my_err(f, x...) \
>>> do { \
>>> char buff[my_errPrintfBuffLen]; \
>>> snprintf(buff, sizeof(buff) - 1, f, ## x); \
>>> buff[my_errPrintfBuffLen - 1] = 0; \
>>
>> I was also going to mention this. It seems a bit belt and braces. Is
>> there any problem with
>>
>> snprintf(buff, sizeof(buff), f, ## x); \
>>
>> and no extra "buff[my_errPrintfBuffLen - 1] = 0;"?
>
> Looks like you are right - snprintf guarantees to put a null character
> at the end. The history of this macro in my code stretches back to use
> with older compilers from long ago, where I was less confident in the
> accuracy of the C library implementation. I can't remember if I
> actually found a problem with a missing termination, or merely thought
> it was a possibility.
Yes, that was why I asked. The sn* family predate the C99 standard but
I don't recall any that would not generate a string (unless the size is
zero of course). But then my memory is not what it was, so I asked if
you had had reason to be suspicious.
>> Incidentally, mixing the use of my_errPrintfBuffLen and sizeof buff is
>> less the ideal. I'd either use the defined constant only in the
>> declaration and sizeof buff - 1 in both other places, or, if I felt the
>> need to avoid confusing people with sizeof, I'd use the defined constant
>> everywhere.
>
> Either method would work - I view the two expressions as synonymous and
> interchangeable. It might be a little different if the uses were
> separated over a longer distance in code rather than being adjacent lines.
>
> And I know that some people think it is nice to write "sizeof(buff)",
> others prefer "sizeof buff". I'd rather not argue too much about style
> here.
Same here. I wrote sizeof buff because that's how I write it. I did
not intend to suggest there was any reason to change or re-hash that old
chestnut. The mixing of the constant and sizeof is slightly more than
style, though, since there's a small cognitive cost to checking the
constant. Even if defined just above, you need to check the spelling in
both usages just in case there's some other similar #define for
something else like my_logPrintBuffLen.
<snip>
--
Ben.
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How to fix: [-Wformat-nonliteral] MehdiAmini <atorrses@gmail.com> - 2017-04-07 12:20 +0430
Re: How to fix: [-Wformat-nonliteral] Barry Schwarz <schwarzb@dqel.com> - 2017-04-07 01:28 -0700
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-07 11:58 +0200
Re: How to fix: [-Wformat-nonliteral] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-04-07 11:43 +0100
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-07 13:35 +0200
Re: How to fix: [-Wformat-nonliteral] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-04-07 13:50 +0100
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-07 15:54 +0200
Re: How to fix: [-Wformat-nonliteral] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-04-07 19:35 +0100
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-08 13:41 +0200
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-10 13:52 -0700
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-11 00:18 +0200
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-10 15:43 -0700
Re: How to fix: [-Wformat-nonliteral] Keith Thompson <kst-u@mib.org> - 2017-04-10 16:10 -0700
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-10 16:26 -0700
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-11 11:33 +0200
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-11 08:37 -0700
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-13 00:20 +0200
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-12 15:55 -0700
Re: How to fix: [-Wformat-nonliteral] Keith Thompson <kst-u@mib.org> - 2017-04-12 18:17 -0700
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-14 12:27 +0200
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-14 11:57 -0700
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-17 18:08 +0200
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-17 09:38 -0700
Re: How to fix: [-Wformat-nonliteral] Keith Thompson <kst-u@mib.org> - 2017-04-12 18:13 -0700
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-13 07:37 -0700
Re: How to fix: [-Wformat-nonliteral] Keith Thompson <kst-u@mib.org> - 2017-04-13 08:43 -0700
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-13 11:24 -0700
Re: How to fix: [-Wformat-nonliteral] Keith Thompson <kst-u@mib.org> - 2017-04-13 11:49 -0700
Re: How to fix: [-Wformat-nonliteral] Robert Wessel <robertwessel2@yahoo.com> - 2017-04-13 14:43 -0500
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-13 13:26 -0700
Re: How to fix: [-Wformat-nonliteral] Keith Thompson <kst-u@mib.org> - 2017-04-13 13:32 -0700
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-13 14:27 -0700
Re: How to fix: [-Wformat-nonliteral] Robert Wessel <robertwessel2@yahoo.com> - 2017-04-13 17:39 -0500
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-13 16:16 -0700
Re: How to fix: [-Wformat-nonliteral] Tim Rentsch <txr@alumni.caltech.edu> - 2017-04-16 17:53 -0700
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-13 13:19 -0700
Re: How to fix: [-Wformat-nonliteral] Tim Rentsch <txr@alumni.caltech.edu> - 2017-04-16 17:49 -0700
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-17 18:14 +0200
Re: How to fix: [-Wformat-nonliteral] Keith Thompson <kst-u@mib.org> - 2017-04-17 11:54 -0700
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-17 22:41 +0200
Re: How to fix: [-Wformat-nonliteral] Keith Thompson <kst-u@mib.org> - 2017-04-17 15:02 -0700
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-14 12:40 +0200
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-14 12:10 -0700
Re: How to fix: [-Wformat-nonliteral] Keith Thompson <kst-u@mib.org> - 2017-04-14 13:22 -0700
Re: How to fix: [-Wformat-nonliteral] supercat@casperkitty.com - 2017-04-14 17:14 -0700
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-13 00:20 +0200
Re: How to fix: [-Wformat-nonliteral] MehdiAmini <atorrses@gmail.com> - 2017-04-07 20:29 +0430
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-07 18:42 +0200
Re: How to fix: [-Wformat-nonliteral] MehdiAmini <atorrses@gmail.com> - 2017-04-08 08:04 +0430
Re: How to fix: [-Wformat-nonliteral] Richard Heathfield <rjh@cpax.org.uk> - 2017-04-08 07:51 +0100
Re: How to fix: [-Wformat-nonliteral] MehdiAmini <atorrses@gmail.com> - 2017-04-08 12:11 +0430
Re: How to fix: [-Wformat-nonliteral] Richard Heathfield <rjh@cpax.org.uk> - 2017-04-08 11:38 +0100
Re: How to fix: [-Wformat-nonliteral] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-04-08 18:52 +0100
Re: How to fix: [-Wformat-nonliteral] David Brown <david.brown@hesbynett.no> - 2017-04-08 13:48 +0200
Re: How to fix: [-Wformat-nonliteral] MehdiAmini <atorrses@gmail.com> - 2017-04-08 20:34 +0430
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