Mixing LDFLAGS/inherited_linker_flags between languages/compilers

[Jeff Squyres]

Greetings!  Here's another from-the-wild Libtool report from the Open  
MPI project.

As was recently reported on our users mailing list (thread started  
here: http://www.open-mpi.org/community/lists/users/2009/03/8613.php),  
we have a situation where a user is trying to use the following  
compiler set: gcc, g++, pgf77, pgf90.  gcc and g++ understand the "- 
pthread" command line switch, but pgf77 and pgf90 do not.  I've CC'ed  
the original reported on this mail.

Open MPI builds a few C support libraries; one of them is libmpi.la  
(completely built with gcc).  In libmpi.la, I can see a field  
containing -lpthread:

inherited_linker_flags=' -pthread'

Then Open MPI builds an F90-based library, libmpi_f90.la.  This  
library links against libmpi.la via the following:

libmpi_f90_la_LIBADD = $(top_builddir)/ompi/libmpi.la

Libtool therefore pulls in $inherited_linker_flags from libmpi.la;  
when it tries to use the F90 compiler to make the final link of the  
libmpi_f90.la library, it fails because pgf90 does not understand the - 
pthread switch.  Specifically, Open MPI's Makefile.am ends up issuing  
the following command:

/bin/sh ../../../libtool --mode=link pgf90 -I../../../ompi/include - 
I../../../ompi/include -I. -I. -I../../../ompi/mpi/f90 -export-dynamic  
-o libmpi_f90.la -rpath /home/jsquyres/bogus/lib mpi.lo mpi_sizeof.lo  
mpi_comm_spawn_multiple_f90.lo mpi_testall_f90.lo mpi_testsome_f90.lo  
mpi_waitall_f90.lo mpi_waitsome_f90.lo mpi_wtick_f90.lo  
mpi_wtime_f90.lo ../../../ompi/libmpi.la -lnsl -lutil -lm

(note the lack of -pthread)

which then translates to:

pgf90 -shared -fpic -Mnomain .libs/mpi.o .libs/mpi_sizeof.o .libs/ 
mpi_comm_spawn_multiple_f90.o .libs/mpi_testall_f90.o .libs/ 
mpi_testsome_f90.o .libs/mpi_waitall_f90.o .libs/ 
mpi_waitsome_f90.o .libs/mpi_wtick_f90.o .libs/mpi_wtime_f90.o -Wl,- 
rpath -Wl,/users/jsquyres/svn/ompi/ompi/.libs -Wl,-rpath -Wl,/users/ 
jsquyres/svn/ompi/orte/.libs -Wl,-rpath -Wl,/users/jsquyres/svn/ompi/ 
opal/.libs -Wl,-rpath -Wl,/home/jsquyres/bogus/lib -L/users/jsquyres/ 
svn/ompi/orte/.libs -L/users/jsquyres/svn/ompi/opal/.libs ../../../ 
ompi/.libs/libmpi.so /users/jsquyres/svn/ompi/orte/.libs/libopen- 
rte.so /users/jsquyres/svn/ompi/opal/.libs/libopen-pal.so -ldl -lnsl - 
lutil -lm -pthread -Wl,-soname -Wl,libmpi_f90.so.0 -o .libs/ 
libmpi_f90.so.0.0.0

(note the addition of -pthread)

Is there anything that can be done about this, perchance?  I'm not  
quite sure what the proper fix would be, but I thought I'd ask anyway...

--
Jeff Squyres
Cisco Systems