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Groups > comp.lang.c > #107808
| From | Ben Bacarisse <ben.usenet@bsb.me.uk> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: How to fix: [-Wformat-nonliteral] |
| Date | 2017-04-07 11:43 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <87shlkv6om.fsf@bsb.me.uk> (permalink) |
| References | <oc7g6c$lpq$1@dont-email.me> <oc7nm7$d6i$1@dont-email.me> |
David Brown <david.brown@hesbynett.no> writes:
> On 07/04/17 09:50, MehdiAmini wrote:
<snip>
>> vfprintf(stderr,s,args);
<snip>
>> I get:
>> warning: format string is not a string literal [-Wformat-nonliteral]
>> vfprintf(stderr,s,args);
<snip>
> Another poster showed you how to disable the warning.
<snip>
> So it would be /much/ safer to have the function as:
>
> noreturn void my_err_s(const char * const s)
> {
> if ((s == NULL) || (*s == '\0')) {
> fprintf(stderr, "Please provide a proper message for "
> "my_err function.\n");
> exit(EXIT_FAILURE);
> }
> fprintf(stderr, "%s\n", s);
> exit(EXIT_FAILURE);
> }
>
> #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; \
> my_err_s(buff); \
> } while (0)
>
> This makes any formatting be handled locally in the function that calls
> my_err, where the compiler can see the format string as a literal and
> check the format against the actual parameters used. (There is, IIRC, a
> slight gcc'ism in the token pasting here to get the commas right even if
> my_err is called with no extra parameters. But I expect clang supports
> the same feature.)
There are two GNUisms -- one is the comma pasting trick to handle zero
variable arguments, and the other is naming the variable arguments as x.
In fact, you don't need either as there is always one required
argument. This is standard C99 and up:
#define my_err(...) \
do { \
char buff[my_errPrintfBuffLen]; \
snprintf(buff, sizeof(buff) - 1, __VA_ARGS__); \
buff[my_errPrintfBuffLen - 1] = 0; \
my_err_s(buff); \
} while (0)
--
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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