Russ Allbery <r...@debian.org> writes: > Russ Allbery <r...@debian.org> writes: >> Kurt Roeckx <k...@roeckx.be> writes: > >>> So it looks to me that _REENTRANT is only used to make some functions >>> like getlogin_r available. > >> I believe that's correct, and the discussion at the last DebConf reached >> the same conclusion. I think this bit in Policy is obsolete. I already >> closed a Lintian bug about it a while back. > >> You may separately need _REENTRANT to get prototypes, but using the right >> feature test macros to get prototypes is a completely different issue and >> I don't think we need to leave this in Policy just for that (otherwise, >> we'd need to talk about GNU_SOURCE and whatnot as well, and I don't see a >> need to go there right now). > >>> I think that libraries in Debian should never change behaviour based on >>> _REENTRANT. If a library can be build to either support threads or not, >>> it should be compiled to support threads. It might also want to provide >>> one that does and one that doesn't so that you can link to either one, >>> but I would like to discourage that, and the default library should be >>> the one that supports threads. And if it does provide 2 libraries, the >>> header files for both should be the same and not depend on _REENTRANT. > >> I think I agree. Could someone propose a wording change to Policy to say >> what we really mean here rather than focusing on _REENTRANT? > > Here's an attempt at that. I'm not sure if this says everything that > needs to be said, but I'm not sure what else to say. > > I considered saying, as Kurt does above, that two libraries could be > provided, one with thread support and one without, but this poses some > serious problems because both libraries could be loaded into the same > process space and then conflict. Doing this properly requires symbol > versioning or some other similar mechanism, and at that point I think > we're getting into something that's too difficult and specific to describe > in Policy. I think I'd rather just let the "should" rather than "must" > provide wiggle-room for that. > > Objections or seconds?
I don't think it should reference _REENTRANT any more for modern GNU/Linux system like Debian. LinuxThreads is an old thread implementation -- see http://pauillac.inria.fr/~xleroy/linuxthreads/ -- that is not used any more. It is not even packaged in Debian. The only need for _REENTRANT I know is OSF/1: # On OSF/1, the compiler needs the flag -D_REENTRANT so that it # groks <pthread.h>. cc also understands the flag -pthread, but # we don't use it because 1. gcc-2.95 doesn't understand -pthread, # 2. putting a flag into CPPFLAGS that has an effect on the linker # causes the AC_TRY_LINK test below to succeed unexpectedly, # leading to wrong values of LIBTHREAD and LTLIBTHREAD. CPPFLAGS="$CPPFLAGS -D_REENTRANT" and Solaris: # Some systems optimize for single-threaded programs by default, and # need special flags to disable these optimizations. For example, the # definition of 'errno' in <errno.h>. case "$host_os" in ... solaris*) CPPFLAGS="$CPPFLAGS -D_REENTRANT" ;; GNU/Linux doesn't need it as far as I have been able to determine. getlogin_r appears to be declared by default now, /usr/include/unistd.h says: #if defined __USE_REENTRANT || defined __USE_POSIX199506 ... extern int getlogin_r (char *__name, size_t __name_len) __nonnull ((1)); But __USE_POSIX199506 is defined by default. Lacking any real evidence of the need of _REENTRANT, I have long since removed all uses of _REENTRANT in my projects (and gnulib) and these projects are used in multi-threaded environments without problem. On the other hand, I know that some Debian packages re-add _REENTRANT. Thus, I would suggest simply saying this: <p> Libraries should be built with threading support and to be thread-safe if the library supports this. </p> Alternatively, provide the _real_ rationale for _REENTRANT. I'm pretty sure LinuxThreads isn't a valid rationale for it these days -- or am I wrong? /Simon > diff --git a/policy.sgml b/policy.sgml > index bad28af..1ffe148 100644 > --- a/policy.sgml > +++ b/policy.sgml > @@ -7225,10 +7225,10 @@ INSTALL = install -s # (or use strip on the files in > debian/tmp) > for C files) will need to be compiled twice, for the normal > case. > </p> > + > <p> > - You must specify the gcc option <tt>-D_REENTRANT</tt> > - when building a library (either static or shared) to make > - the library compatible with LinuxThreads. > + Libraries should be built with threading support and to be > + thread-safe if the library supports this. > </p> > > <p> -- To UNSUBSCRIBE, email to debian-policy-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/87k4pbirwq....@mocca.josefsson.org
