This approach is cleaner than the previous one -- use a temporary

shell variable to avoid setting the OMPI $libpath twice in
$LD_LIBRARY_PATH.  Many thanks to Glenn Morris.

This commit was SVN r8883.

orte/mca/pls/rsh/pls_rsh_module.c

@@ -801,58 +801,28 @@ int orte_pls_rsh_launch(orte_jobid_t jobid)
                                     prefix_dir,
                                     prefix_dir, mca_pls_rsh_component.orted);
                         }
-                        /*
-                         * This needs cleanup:
-                         * Only if the LD_LIBRARY_PATH is set, prepend our prefix/lib to it....
-                         */
                         if (remote_csh) {
-                            /* This requires some explanation.  :-)
-                               Optimally, we would like to be able to
-                               execute the following [pseudocode] in a
-                               single csh-based line:
-
-                               if (not_set(LD_LIBRARY_PATH)) setenv LD_LIBRARY_PATH <path> else setenv LD_LIBRARY_PATH ${LD_LIBRARY_PATH}:<path> endif
-
-                               But we can't because tcsh will try to
-                               evaluate the entire string at once --
-                               so if LD_LIBRARY_PATH is not yet
-                               defined, the ${LD_LIBRARY_PATH} in the
-                               else clause will cause an error.
-                               Specifically, tcsh is not smart enough
-                               to *not* interpret the "else" clause if
-                               the conditional is true (hence, the
-                               error).  
-
-                               The only way to make tcsh not error (in
-                               a portable way) is to force
-                               LD_LIBRARY_PATH to have a value.  :-(
-
-                               Specifically: if LD_LIBRARY_PATH is
-                               *not* set, then set it to the correct
-                               value.  At this point in execution,
-                               we'll know that LD_LIBRARY_PATH is
-                               guaranteed to have a value (because
-                               either we just set it, or it already
-                               had a value).  So we can safely prefix
-                               LD_LIBRARY_PATH with the correct value.
-
-                               In the case where LD_LIBRARY_PATH was
-                               not already set, the end result is that
-                               it will contain Open MPI's libdir
-                               twice.  This is hardly elegant, but is
-                               avoids this messy tcsh evaluation
-                               issue.  :-(
-                             */
+                            /* [t]csh is a bit more challenging -- we
+                               have to check whether LD_LIBRARY_PATH
+                               is already set before we try to set it.
+                               Must be very careful about obeying
+                               [t]csh's order of evaluation and not
+                               using a variable before it is defined.
+                               See this thread for more details:
+                               http://www.open-mpi.org/community/lists/users/2006/01/0517.php. */
                             asprintf (&argv[local_exec_index],
-                                    "set path = ( %s/bin $path ) ; "
-                                    "if ( \"$?LD_LIBRARY_PATH\" == 0 ) "
-                                    "setenv LD_LIBRARY_PATH %s/lib ; "
-                                    "setenv LD_LIBRARY_PATH %s/lib:$LD_LIBRARY_PATH ; "
-                                    "%s/bin/%s",
-                                    prefix_dir,
-                                    prefix_dir,
-                                    prefix_dir,
-                                    prefix_dir, mca_pls_rsh_component.orted);
+                                      "set path = ( %s/bin $path ) ; "
+                                      "if ( $?LD_LIBRARY_PATH == 1 ) "
+                                      "set OMPI_have_llp ; "
+                                      "if ( $?LD_LIBRARY_PATH == 0 ) "
+                                      "setenv LD_LIBRARY_PATH %s/lib ; "
+                                      "if ( $?OMPI_have_llp == 1 ) "
+                                      "setenv LD_LIBRARY_PATH %s/lib:$LD_LIBRARY_PATH ; "
+                                      "%s/bin/%s",
+                                      prefix_dir,
+                                      prefix_dir,
+                                      prefix_dir,
+                                      prefix_dir, mca_pls_rsh_component.orted);
                         }
                     }
                 }