[PATCH v2] Fix checking for valid argument of --dpi

[Walter Harms]

> Pali Rohár <pali.rohar at gmail.com> hat am 29. Dezember 2018 um 18:45
> geschrieben:
> 
> 
> On Monday 26 November 2018 22:17:24 Pali Rohár wrote:
> > Function strtod() sets strtod_error to the pointer of the first invalid
> > character and therefore it does not have to be first character from input.
> > When input is valid then it points to nul byte. Conversion error is
> > indicated by setted errno. Zero-length argument, non-positive DPI or DPI
> > with trailing or leading whitespaces is invalid too.
> > 
> > Update also error message about invalid argument.
> > 
> > Signed-off-by: Pali Rohár <pali.rohar at gmail.com>
> > 
> > --
> > 
> > Changes since v1:
> > * Get same error message for `xrandr --dpi ''` and `xrandr --dpi ' '`
> > * Make the check for dpi <= 0
> > * Do not accept leading whitespaces (trailing were already disallowed)
> > ---
> >  xrandr.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/xrandr.c b/xrandr.c
> > index ce3cd91..4baa075 100644
> > --- a/xrandr.c
> > +++ b/xrandr.c
> > @@ -40,6 +40,7 @@
> >  #include <inttypes.h>
> >  #include <stdarg.h>
> >  #include <math.h>
> > +#include <ctype.h>
> >  
> >  #ifdef HAVE_CONFIG_H
> >  #include "config.h"
> > @@ -3118,8 +3119,9 @@ main (int argc, char **argv)
> >  	if (!strcmp ("--dpi", argv[i])) {
> >  	    char *strtod_error;
> >  	    if (++i >= argc) argerr ("%s requires an argument\n", argv[i-1]);
> > +	    errno = 0;
> >  	    dpi = strtod(argv[i], &strtod_error);
> > -	    if (argv[i] == strtod_error)
> > +	    if (!argv[i][0] || isspace(argv[i][0]) || *strtod_error || errno ||
> > dpi <= 0)
> >  	    {
> >  		dpi = 0.0;
> >  		dpi_output_name = argv[i];


Why spending so much effort ? 
Using atoi(argv[i]) and checking for an invalid value seems fine.
Special cases like NAN do not matter here.

BTW: leading whitespaces are ignored with strtod() (so far i know)

just my 2 cents
re,
 wh



> > @@ -3569,7 +3571,7 @@ main (int argc, char **argv)
> >  	    XRROutputInfo	*output_info;
> >  	    XRRModeInfo	*mode_info;
> >  	    if (!dpi_output)
> > -		fatal ("Cannot find output %s\n", dpi_output_name);
> > +		fatal ("%s is not valid DPI nor valid output\n", dpi_output_name);
> >  	    output_info = dpi_output->output_info;
> >  	    mode_info = dpi_output->mode_info;
> >  	    if (output_info && mode_info && output_info->mm_height)
> 
> Hello, can you review this v2 patch?
> 
> -- 
> Pali Rohár
> pali.rohar at gmail.com
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