Re: (x)gethostname

[Simon Josefsson]

Brian Dessent <address@hidden> writes:

> Simon Josefsson wrote:
>
>> 3) Is there any chance that the #define gethostname rpl_gethostname and
>> replacement prototype of gethostname in gnulib's unistd.h will cause
>> problems?  Consider that gethostname in winsock2.h is declared with
>> PASCAL calling conventions, so the prototype is not the same as the one
>> that gnulib uses.  That may cause problems in some weird situations, but
>> I can't see them right now.  The self test works fine.
>
> I was invisioning a situation where a package that is already
> Winsock-aware (i.e. does its own WSAStartup) erroniously adds the
> gethostname module.  Then the replacement would be pulled in, resulting
> in a Startup+Cleanup when it's not desired, which would potentially
> trash any open socket operations the app might have at that point. 
> However, the MSDN page does say that Startup/Cleanup are reference
> counted and the teardown is only done in the case where the count goes
> to 0.  So as long as the replacement gethostname always does them in
> pairs this should be fine.

Right, that was how I read the documentation as well.

>> 4) Is calling WSAStartup/WSACleanup in each gnulib replacement module a
>> good idea?  I could easily argue that it is simpler for everyone if
>> gnulib simply say that if you care about Windows portability, you need
>> to call WSAStartup+WSACleanup yourself.  The gnulib module 'sockets'
>> could be used for this, and then the 'gethostname' module may not need
>> to depend directly on the 'sockets' module.
>
> I think neglecting to WSAStartup is one of the most common mistakes when
> porting socket applications to Win32.  Couldn't there be a gnulib module
> that perhaps wraps main() to first call WSAStartup() and
> atexit(WSACleanup()) so that portable sockets programs don't have to see
> any of it?

This wouldn't work well for libraries.  I think documenting this, and
providing useful gnulib modules to make sure the WSAStartup gets called
is sufficient.

> (I'm not even sure if the atexit is really necessary -- MSDN does say
> "There must be a call to WSACleanup for each successful call to
> WSAStartup" but that is in the context of explaining the reference
> count.  I'm nearly certain that the required cleanup is also done when
> the process terminates normally.)

Yeah, I think so too.

>> 5) Does this result in the right thing on cygwin?  I suppose it should
>> detect that gethostname is present and not do anything beyond that.
>
> It looks fine here.  WINDOWS_SOCKETS is not defined and the replacement
> is not used.

Great.

/Simon