Date: Wed, 4 Feb 2015 10:35:48 -0800 From: John-Mark Gurney <jmg@funkthat.com> To: Erich Dollansky <erichsfreebsdlist@alogt.com> Cc: freebsd-stable@freebsd.org Subject: Re: top, fixed buffer length in utils.c Message-ID: <20150204183548.GA27763@funkthat.com> In-Reply-To: <20150204170947.17764dff@B85M-HD3-0.alogt.com> References: <20150201175159.7fa88d16@B85M-HD3-0.alogt.com> <20150203003307.GG27103@funkthat.com> <20150203200135.57c8c236@B85M-HD3-0.alogt.com> <20150204074235.GX27103@funkthat.com> <20150204170947.17764dff@B85M-HD3-0.alogt.com>
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Erich Dollansky wrote this message on Wed, Feb 04, 2015 at 17:09 +0800:
> Hi,
>
> On Tue, 3 Feb 2015 23:42:35 -0800
> John-Mark Gurney <jmg@funkthat.com> wrote:
>
> > Erich Dollansky wrote this message on Tue, Feb 03, 2015 at 20:01
> > +0800:
> > > On Mon, 2 Feb 2015 16:33:07 -0800
> > > John-Mark Gurney <jmg@funkthat.com> wrote:
> > >
> > > > Erich Dollansky wrote this message on Sun, Feb 01, 2015 at 17:51
> > > > +0800:
> > > > > int can be 64 bits on a amd64 machine. Why is the author of this
> > > > > code so sure that we will never cross the 32 bit boundary?
> > > >
> > > > Per others, int is currently 32bits on all platforms we support...
> > > >
> > > > I guess adding:
> > > > CTASSERT(sizeof(int) <= 4);
> > > >
> > > > would help fix your concern? at least now the expectation is
> > > > codified and if it breaks, the build will break..
> > > >
> > > of course. Either avoid the run-time problem or get an error message
> > > and things cannot create hidden problem.
> >
> > Ok, I've generated this patch:
> > Index: utils.c
> > ===================================================================
> > --- utils.c (revision 277938)
> > +++ utils.c (working copy)
> > @@ -58,6 +58,7 @@ char *str;
> > * ever convert will be 2^32-1,
> > which is 10
> > * digits.
> > */
> > +_Static_assert(sizeof(int) <= 4, "buffer too small for this sized
> > int");
> > char *itoa(val)
> >
> Wait, shouldn't it the other way around? It will break when sizeof
> (int) is greater than 4?
No, asserts trigger when the statement is false... I verified this
by changing 4 to 2 and seeing that it failed (triggered) to compile...
> > I couldn't use CTASSERT because including sys/param.h and sys/systm.h
> > per man page didn't work.. apparently for userland it's different and
> > requires additional headers... It appears that we define it in
> > sys/cdefs.h which gets included, so this work for both clang and
> > gcc...
> >
> > I'll commit it soon unless someone objects...
> >
> Thanks!
>
> Erich
--
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"All that I will do, has been done, All that I have, has not."
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