Ensure to instantiate MPI_F_STATUS_IGNORE and MPI_F_STATUSES_IGNORE.

Thanks to Anthony Chan for pointing this out.

Note that these will only work for the Fortran compiler that Open MPI
was configured with -- since these values, are, by definition,
single-value, they cannot support all 4 values that Open MPI may
generate for the different Fortran name-mangling schemes.  A lengthy
comment in ompi_mpi_init.c explains this in more detail.  Added to the
README to explain this situation, as well as the forthcoming
.TRUE. Fortran fixes.

This commit was SVN r8231.

README

@@ -127,7 +127,7 @@ base as of this writing (21 Nov 2005):
          --with-wrapper-fcflags=-Munixlogical ...
 
   This will be fixed in a future version of Open MPI.
-
+                                   
 - For any version of the Intel compiler >= 8.0, the default value for
   .TRUE. is -1.  Open MPI does not currently handle this correctly.
   As such, the "-fpscomp logicals" option must be used with the Intel
@@ -152,6 +152,38 @@ base as of this writing (21 Nov 2005):
 
   This will be fixed in a future version of Open MPI.
 
+- Open MPI will build bindings suitable for all common forms of
+  Fortran 77 compiler symbol mangling on platforms that support it
+  (e.g., Linux).  On platforms that do not support weak symbols (e.g.,
+  OS X), Open MPI will build Fortran 77 bindings just for the compiler
+  that Open MPI was configured with.  
+
+  Hence, on platforms that support it, if you configure Open MPI with
+  a Fortran 77 compiler that uses one symbol mangling scheme, you can
+  successfully compile and link MPI Fortran 77 applications with a
+  Fortran 77 compiler that uses a different symbol mangling scheme.
+
+  NOTE: For platforms that support the multi-Fortran-compiler bindings
+  (i.e., weak symbols are supported), due to limitations in the MPI
+  standard and in Fortran compilers, it is not possible to hide these
+  differences in all cases.  Specifically, the following two cases may
+  not be portable between different Fortran compilers:
+
+  1. The C constants MPI_F_STATUS_IGNORE and MPI_F_STATUSES_IGNORE
+     will only compare properly to Fortran applications that were
+     created with Fortran compilers that that use the same
+     name-mangling scheme as the Fortran compiler that Open MPI was
+     configured with.
+
+  2. Fortran compilers may have different values for the logical
+     .TRUE. constant.  As such, any MPI function that uses the fortran
+     LOGICAL type may only get .TRUE. values back that correspond to
+     the the .TRUE. value of the Fortran compiler that Open MPI was
+     configured with.
+
+  You can use the ompi_info command to see the Fortran compiler that
+  Open MPI was configured with.
+
 - The MPI and run-time layers do not free all used memory properly
   during MPI_FINALIZE.
 

ompi/runtime/ompi_mpi_init.c

@@ -45,6 +45,7 @@
 #include "orte/mca/errmgr/errmgr.h"
 
 #include "ompi/include/constants.h"
+#include "ompi/mpi/f77/constants.h"
 #include "ompi/runtime/mpiruntime.h"
 #include "ompi/runtime/params.h"
 #include "ompi/communicator/communicator.h"
@@ -87,6 +88,52 @@ opal_thread_t *ompi_mpi_main_thread = NULL;
 
 bool ompi_mpi_maffinity_setup = false;
 
+/*
+ * These variables are here, rather than under ompi/mpi/c/foo.c
+ * because it is not sufficient to have a .c file that only contains
+ * variables -- you must have a function that is invoked from
+ * elsewhere in the code to guarantee that all linkers will pull in
+ * the .o file from the library.  Hence, although these are MPI
+ * constants, we might as well just define them here (i.e., in a file
+ * that already has a function that is guaranteed to be linked in,
+ * rather than make a new .c file with the constants and a
+ * corresponding dummy function that is invoked from this function).
+ *
+ * NOTE: See the big comment in ompi/mpi/f77/constants.h about why we
+ * have four symbols for each of the common blocks (e.g., the Fortran
+ * equivalent(s) of MPI_STATUS_IGNORE).  Here, we can only have *one*
+ * value (not four).  So the only thing we can do is make it equal to
+ * the fortran compiler convention that was selected at configure
+ * time.  Note that this is also true for the value of .TRUE. from the
+ * Fortran compiler, so even though Open MPI supports all four Fortran
+ * symbol conventions, it can only support one convention for the two
+ * C constants (MPI_FORTRAN_STATUS[ES]_IGNORE) and only support one
+ * compiler for the value of .TRUE.  Ugh!!
+ *
+ * Note that the casts here are ok -- we're *only* comparing pointer
+ * values (i.e., they'll never be de-referenced).  The global symbols
+ * are actually of type (ompi_fortran_common_t) (for alignment
+ * issues), but MPI says that MPI_F_STATUS[ES]_IGNORE must be of type
+ * (MPI_Fint*).  Hence, we have to cast to make compilers not
+ * complain.
+ */
+
+#if OMPI_F77_CAPS
+MPI_Fint *MPI_F_STATUS_IGNORE = (MPI_Fint*) &MPI_FORTRAN_STATUS_IGNORE;
+MPI_Fint *MPI_F_STATUSES_IGNORE = (MPI_Fint*) &MPI_FORTRAN_STATUSES_IGNORE;
+#elif OMPI_F77_PLAIN
+MPI_Fint *MPI_F_STATUS_IGNORE = (MPI_Fint*) &mpi_fortran_status_ignore;
+MPI_Fint *MPI_F_STATUSES_IGNORE = (MPI_Fint*) &mpi_fortran_statuses_ignore;
+#elif OMPI_F77_SINGLE_UNDERSCORE
+MPI_Fint *MPI_F_STATUS_IGNORE = (MPI_Fint*) &mpi_fortran_status_ignore_;
+MPI_Fint *MPI_F_STATUSES_IGNORE = (MPI_Fint*) &mpi_fortran_statuses_ignore_;
+#elif OMPI_F77_DOUBLE_UNDERSCORE
+MPI_Fint *MPI_F_STATUS_IGNORE = (MPI_Fint*) &mpi_fortran_status_ignore__;
+MPI_Fint *MPI_F_STATUSES_IGNORE = (MPI_Fint*) &mpi_fortran_statuses_ignore__;
+#else
+#error Unrecognized Fortran 77 name mangling scheme
+#endif
+
 
 int ompi_mpi_init(int argc, char **argv, int requested, int *provided)
 {