svn commit: r254600 - head/lib/libutil

Jilles Tjoelker jilles at stack.nl
Wed Aug 21 20:27:31 UTC 2013


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.

-- 
Jilles Tjoelker


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