Re: [gpsd-dev] [PATCH v3 1/1] gps2udp: reset errno after successful getaddrinfo call

[Mike Frysinger]

On Friday 03 January 2014 10:18:42 Ferry Huberts wrote:
> On 03/01/14 16:00, Mike Frysinger wrote:
> > On Friday 03 January 2014 09:29:29 Ferry Huberts wrote:
> >> On 03/01/14 15:18, Mike Frysinger wrote:
> >>> On Friday 03 January 2014 08:33:47 Ferry Huberts wrote:
> >>>> It may return errno==2 ("No such file or directory") when the file
> >>>> /etc/gai.conf is not present.
> >>>> 
> >>>> The observed effect was that the port number conversion considered
> >>>> a perfectly valid port number as invalid.
> >>> 
> >>> you still haven't really explained why this is the way to go. 
> >>> functions do not "return errno".  they return real values, and any
> >>> code calling those functions need to first check the return value
> >>> *before* ever looking at errno.
> >> 
> >> Which is exactly what happens here: the code bails out if the function
> >> call is not successful.
> > 
> > what code is bailing where ?
> 
> please do read the code:

i did read the code

> >     if ((ret = getaddrinfo(host, service, &hints, &result))) {
> >     return NL_NOHOST;
> >     }
> 
> returns from the function (with return value NL_NOHOST) when the
> getaddrinfo call is not successful (returns a non-zero value).

except you didn't reset the errno in that case.  you reset it when the 
function succeeded.

so, once again, what is the actual problem you're trying to fix ?

> >> The function call may set errno even though it succeeds.
> > 
> > that is not a bug
> 
> exactly, which is why we must reset errno, because otherwise other
> functions are affected.

no, no they are not
-mike

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