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Groups > comp.unix.programmer > #1074
| From | Nobody <nobody@nowhere.com> |
|---|---|
| Subject | Re: C Code "sanity checking" tools |
| Date | 2011-08-08 14:01 +0100 |
| Message-Id | <pan.2011.08.08.13.01.31.817000@nowhere.com> |
| Newsgroups | comp.unix.programmer |
| References | <4e3fc1c6$0$940$c3e8da3$9f400e27@news.astraweb.com> |
| Organization | Zen Internet |
On Mon, 08 Aug 2011 12:00:11 +0100, Martin Crouch wrote:
> If I write some code like this:
>
> #include <stdio.h>
> int main(void)
> {
> char mystring[5];
>
> printf("String:%s\n",mystring);
>
> return 0;
> }
> }
> It compiles okay (no warnings),
Really? You should get an error due to the extra closing brace.
> but when runs it has undefined results
> because I've not put anything into mystring before attempting to print it,
> so it gets whatever garbage is left in memory.
>
> Are there any "pre-compiler" code analysis tools out there that would pick
> up this sort of problem? The platform is sparc Solaris 10.
In general, "gcc -O -Wall ..." will warn about using uninitialised
variables. It won't work in the specific case above because gcc doesn't
know that the printf() call will access the elements of mystring. If the
format string had "%p" instead of "%s":
printf("String:%p\n",mystring);
there wouldn't actually be any error in the code. OTOH, this:
printf("String:%c\n",mystring[0]);
will result in a warning (with "-O -Wall") because it can see the access.
Similarly, this:
scanf("String:%s\n",mystring);
doesn't have any issues, because the array is written rather than read.
Note that printf() is a harder case because it's variadic; otherwise, it
would be reasonable to assume that an array passed as a "const char *"
argument is going to be read and should contain something (there are cases
where this needn't be true, e.g. the "%p" example, but any static analysis
tool is going to give the occasional false result).
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C Code "sanity checking" tools Martin Crouch <spamspamspam@spaml.com> - 2011-08-08 12:00 +0100
Re: C Code "sanity checking" tools Richard Kettlewell <rjk@greenend.org.uk> - 2011-08-08 12:09 +0100
Re: C Code "sanity checking" tools Fritz Wuehler <fritz@spamexpire-201108.rodent.frell.theremailer.net> - 2011-08-09 08:50 +0200
Re: C Code "sanity checking" tools Måns Rullgård <mans@mansr.com> - 2011-08-09 10:55 +0100
Re: C Code "sanity checking" tools Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-09 14:15 +0100
Re: C Code "sanity checking" tools Nomen Nescio <nobody@dizum.com> - 2011-08-10 01:58 +0200
Re: C Code "sanity checking" tools Nomen Nescio <nobody@dizum.com> - 2011-08-10 12:29 +0200
Re: C Code "sanity checking" tools Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-08-09 14:17 +0100
Re: C Code "sanity checking" tools Keith Thompson <kst-u@mib.org> - 2011-08-09 09:17 -0700
Re: C Code "sanity checking" tools Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-08-09 17:36 +0100
Re: C Code "sanity checking" tools Keith Thompson <kst-u@mib.org> - 2011-08-09 12:19 -0700
Re: C Code "sanity checking" tools Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-08-09 20:36 +0100
Re: C Code "sanity checking" tools Michael Press <rubrum@pacbell.net> - 2011-08-09 19:24 -0700
Re: C Code "sanity checking" tools Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-08-10 10:27 +0100
Re: C Code "sanity checking" tools Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-08-10 14:01 +0100
Re: C Code "sanity checking" tools "io_x" <a@b.c.invalid> - 2011-08-13 09:42 +0200
Re: C Code "sanity checking" tools Keith Thompson <kst-u@mib.org> - 2011-08-13 16:04 -0700
Re: C Code "sanity checking" tools Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-08-14 19:46 +0100
Re: C Code "sanity checking" tools Ian Collins <ian-news@hotmail.com> - 2011-08-08 23:12 +1200
Re: C Code "sanity checking" tools Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-08 15:35 +0100
Re: C Code "sanity checking" tools Martin Crouch <spamspamspam@spaml.com> - 2011-08-08 16:05 +0100
Re: C Code "sanity checking" tools Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-08 22:57 +0100
Re: C Code "sanity checking" tools Måns Rullgård <mans@mansr.com> - 2011-08-08 23:32 +0100
Re: C Code "sanity checking" tools Ian Collins <ian-news@hotmail.com> - 2011-08-09 08:03 +1200
Re: C Code "sanity checking" tools Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-08 22:51 +0100
Re: C Code "sanity checking" tools Ian Collins <ian-news@hotmail.com> - 2011-08-09 10:01 +1200
Re: C Code "sanity checking" tools jt@toerring.de (Jens Thoms Toerring) - 2011-08-08 22:06 +0000
Re: C Code "sanity checking" tools Ian Collins <ian-news@hotmail.com> - 2011-08-09 10:18 +1200
Re: C Code "sanity checking" tools jt@toerring.de (Jens Thoms Toerring) - 2011-08-08 23:25 +0000
Re: C Code "sanity checking" tools Nobody <nobody@nowhere.com> - 2011-08-08 14:01 +0100
Re: C Code "sanity checking" tools Måns Rullgård <mans@mansr.com> - 2011-08-08 14:47 +0100
Re: C Code "sanity checking" tools Martin Crouch <spamspamspam@spaml.com> - 2011-08-08 16:08 +0100
Re: C Code "sanity checking" tools Marc <marc.glisse@gmail.com> - 2011-08-08 15:39 +0000
Re: C Code "sanity checking" tools William Ahern <william@wilbur.25thandClement.com> - 2011-08-08 10:20 -0700
Re: C Code "sanity checking" tools Nobody <nobody@nowhere.com> - 2011-08-09 00:59 +0100
Re: C Code "sanity checking" tools mathog <dmathog@gmail.com> - 2011-08-08 08:48 -0700
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