Date: Wed, 21 Aug 2013 23:37:55 +0200 From: Jilles Tjoelker <jilles@stack.nl> To: Sergey Kandaurov <pluknet@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Andrey Chernov <ache@freebsd.org> Subject: Re: svn commit: r254600 - head/lib/libutil Message-ID: <20130821213755.GA8052@stack.nl> In-Reply-To: <20130821212413.GC52908@omg> References: <201308211646.r7LGk6eV051215@svn.freebsd.org> <5214F72B.7070006@freebsd.org> <20130821190309.GB52908@omg> <20130821202725.GA4991@stack.nl> <20130821212413.GC52908@omg>
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On Thu, Aug 22, 2013 at 01:24:13AM +0400, Sergey Kandaurov wrote:
> On Wed, Aug 21, 2013 at 10:27:25PM +0200, Jilles Tjoelker wrote:
> > On Wed, Aug 21, 2013 at 11:03:10PM +0400, Sergey Kandaurov wrote:
> > > On Wed, Aug 21, 2013 at 09:21:47PM +0400, Andrey Chernov wrote:
> > > > On 21.08.2013 20:46, Sergey Kandaurov wrote:
> > > > > number = strtoumax(buf, &endptr, 0);
> > > > >
> > > > > + if (number == UINTMAX_MAX && errno == ERANGE) {
> > > > > + return (-1);
> > > > > + }
> > > > You need to reset errno before strtoumax() call (errno = 0), because any
> > > > of previous functions may left it as ERANGE.
> > > Thanks for pointing out.
> > > Does the patch look good?
> > > Index: expand_number.c
> > > ===================================================================
> > > --- expand_number.c (revision 254600)
> > > +++ expand_number.c (working copy)
> > > @@ -53,6 +53,8 @@
> > > unsigned shift;
> > > char *endptr;
> > >
> > > + errno = 0;
> > > +
> > > number = strtoumax(buf, &endptr, 0);
> > >
> > > if (number == UINTMAX_MAX && errno == ERANGE) {
> > This may cause the function to set errno=0 if it is successful, which is
> > not allowed for standard library functions from C and POSIX. There may
> > be a problem not only if expand_number() is standardized but also if it
> > is used in the implementation of a standard library function. The best
> > solution is to save and restore errno around this (if [ERANGE] is
> > detected, that is a valid errno value to keep).
> > In an application it is acceptable to set errno=0 without further ado.
> What about this change?
> It changes errno only if it was modified from zero in strtoumax().
> Unconditionally restoring errno after strtoumax() unless ERANGE is
> probably not good as strtoumax() might set different errno (e.g. EINVAL)
> and we might want to keep it as well. Please correct me, if I'm wrong.
> Index: lib/libutil/expand_number.c
> ===================================================================
> --- lib/libutil/expand_number.c (revision 254600)
> +++ lib/libutil/expand_number.c (working copy)
> @@ -50,15 +50,22 @@
> expand_number(const char *buf, uint64_t *num)
> {
> uint64_t number;
> + int saved_errno;
> unsigned shift;
> char *endptr;
>
> + saved_errno = errno;
> + errno = 0;
> +
> number = strtoumax(buf, &endptr, 0);
>
> if (number == UINTMAX_MAX && errno == ERANGE) {
> return (-1);
> }
>
> + if (errno == 0)
> + errno = saved_errno;
> +
> if (endptr == buf) {
> /* No valid digits. */
> errno = EINVAL;
>
This looks good to me.
--
Jilles Tjoelker
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