Re: [gpsd-dev] wsg_separation Issue

[Beat Bolli]

On 06.05.12 02:13, Gary E. Miller wrote:
> Yo Beat!
> 
> On Sat, 05 May 2012 23:23:13 +0200
> Beat Bolli <address@hidden> wrote:
> 
>> On 05.05.12 21:38, Gary E. Miller wrote:
>>> On Fri, 4 May 2012 09:51:38 -0400
>>> "Bywater, Rick (SA-1)" <address@hidden> wrote:
>>>
>>>> I was running Coverity on gpsd-2.39 and it complained about an
>>>> array-bounds issue in geoid.c in the function wsg84_separation.
> 
>> The current code is still wrong IMO:
>>
>>     ilat = (int)floor((90. + lat) / 10);
>>     ilon = (int)floor((180. + lon) / 10);
>>
>>     /* sanity checks to prevent segfault on bad data */
>>     if ((ilat > 90) || (ilat < -90)) {
>>         return 0.0;
>>     }
>>     if ((ilon > 180) || (ilon < -180)) {
>>         return 0.0;
>>     }
>>
>> ilat and ilon are offset so as to be >= 0, but the subsequent test
>> checks the original degree range without offset or divisor. Checking
>> lat and lon above the i{lat,lon} calculation should work.
> 
> Seems to me that keeping the sanity test on the integer, rather than, 
> the float, is the way to go.  So I think you are suggesting the test
> should be:
> 
>      if ((ilat > 18) || (ilat < 0)) {
>          return 0.0;
>      }
>      if ((ilon > 36) || (ilon < 0)) {
>          return 0.0;
>      }
> 
> Do I have it right?

I'd reuse the GEOID_ROW and GEOID_COL constants and merge the two ifs:

    /* sanity checks to prevent segfault on bad data */
    if ((ilat >= GEOID_ROW) || (ilat < 0) ||
        (ilon >= GEOID_COL) || (ilon < 0))
        return 0.0;

But other than that, it looks fine.

Regards,
Beat
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