Re: lib/46661: libpthread shouldn't provide __res_state()

[River Tarnell <river%RT.UK.EU.ORG@localhost>]

The following reply was made to PR lib/46661; it has been noted by GNATS.

From: River Tarnell <river%RT.UK.EU.ORG@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: lib-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
        netbsd-bugs%netbsd.org@localhost
Subject: Re: lib/46661: libpthread shouldn't provide __res_state()
Date: Thu, 5 Jul 2012 17:08:00 +0100

 Christos Zoulas:
 >  | From an API point of view I don't see why _res shouldn't work in
 >  | programs linked against -lpthread[...]
 >  | Is there an issue with NetBSD's
 >  | implementation that prevents this from working?
 
 >  No there is not, but there is no way to know that the program will use
 >  one thread to call the resolver once linking with -lpthread.
 
 So because a program *may* use _res wrongly, *all* programs that use 
 _res (and libpthread) are broken, even those that use it correctly?
 
 >  | I don't disagree, but these functions are used in current, existing code
 >  | and break popular software (such as Postfix) in certain configurations
 >  | on NetBSD.  For that reason alone it would be nice if they worked as
 >  | they do on other platforms.
 >  
 >  Postfix itself is not broken, other things linking in it are.
 
 Postfix is broken in the sense that it doesn't work (e.g. pkg/44656).
 
 The problem is that it's not clear whose fault it is.  Postfix is the 
 one calling _res, but it's entirely single-threaded, so there's nothing 
 wrong with that.  It links against the PostgreSQL client library, libpq.  
 libpq does not use _res (it uses the MP-safe resolv interface), but it 
 is MP-safe itself, and pulls in libpthread.  As a result, Postfix 
 doesn't work.
 
 >  This is similar to the issue with have
 >  with mutexes: requiring pthread_mutex_init() before using them;
 >  other OS's don't and people claim NetBSD is broken.
 
 The pthread API requires that pthread_mutex_init() be called, doesn't 
 it?  So, a program not doing so is clearly wrong.
 
 >  If programs want to play with _res from a threaded context, they are
 >  broken and should be fixed.
 
 But the program is single-threaded; it just happens to link against 
 libpthread.  Why shouldn't that work?
 
        - river.