It turns out that Fortran has some specific rules about copying

strings.  Here's one: no matter how much of the string you copy, the
destination string must be space-padded for the entire remaining area.
Specifically, even if you call MPI_INFO_GET and tell MPI to only copy
a max of N characters of the value into the result string, if the
Fortran string is M characters (where M > N), MPI must space-pad the
remaining (M-N) characters to be spaces.  So you're supposed to obey
the argument to MPI_INFO_GET... sorta.

Precedents:

 * http://www.ibiblio.org/pub/languages/fortran/ch2-13.html
 * LAM/MPI
 * Sun CT MPI

This commit was SVN r11412.

ompi/mpi/f77/error_string_f.c

@@ -82,8 +82,6 @@ void mpi_error_string_f(MPI_Fint *errorcode, char *string,
 					 ));
     if (MPI_SUCCESS == OMPI_FINT_2_INT(*ierr)) {
         OMPI_SINGLE_INT_2_FINT(resultlen);
-        string_len = (string_len < MPI_MAX_ERROR_STRING) ?
-            string_len : MPI_MAX_ERROR_STRING;
         if (OMPI_SUCCESS != (ret = ompi_fortran_string_c2f(c_string, string,
                                                            string_len))) {
             c_err = OMPI_ERRHANDLER_INVOKE(MPI_COMM_WORLD, ret, FUNC_NAME);

ompi/mpi/f77/file_get_view_f.c

@@ -74,6 +74,6 @@ void mpi_file_get_view_f(MPI_Fint *fh, MPI_Offset *disp,
         *disp = (MPI_Fint) c_disp;
         *etype = MPI_Type_c2f(c_etype);
         *filetype = MPI_Type_c2f(c_filetype);
-        ompi_fortran_string_c2f(c_datarep, datarep, MPI_MAX_DATAREP_STRING);
+        ompi_fortran_string_c2f(c_datarep, datarep, datarep_len);
     }
 }

ompi/mpi/f77/get_processor_name_f.c

@@ -80,8 +80,8 @@ void mpi_get_processor_name_f(char *name, MPI_Fint *resultlen, MPI_Fint *ierr,
     if (MPI_SUCCESS == OMPI_FINT_2_INT(*ierr)) {
         OMPI_SINGLE_INT_2_FINT(resultlen);
 
-        name_len = (name_len < OMPI_FINT_2_INT(*resultlen)) ?
-            name_len : OMPI_FINT_2_INT(*resultlen);
+        /* Use the full length of the Fortran string, not *resultlen.
+           See comment in ompi/mpi/f77/strings.c. */
         if (OMPI_SUCCESS != (ret = ompi_fortran_string_c2f(c_name, name,
                                                            name_len))) {
             c_err = OMPI_ERRHANDLER_INVOKE(MPI_COMM_WORLD, ret, FUNC_NAME);

ompi/mpi/f77/info_get_f.c

@@ -91,8 +91,8 @@ void mpi_info_get_f(MPI_Fint *info, char *key, MPI_Fint *valuelen,
     if (MPI_SUCCESS == OMPI_FINT_2_INT(*ierr)) {
         OMPI_SINGLE_INT_2_LOGICAL(flag);
 
-        value_len = (value_len < OMPI_FINT_2_INT(*valuelen)) ?
-            value_len : OMPI_FINT_2_INT(*valuelen);
+        /* Use the full length of the Fortran string, not *valuelen.
+           See comment in ompi/mpi/f77/strings.c. */
         if (OMPI_SUCCESS != (ret = ompi_fortran_string_c2f(c_value, value,
                                                            value_len))) {
             c_err = OMPI_ERRHANDLER_INVOKE(MPI_COMM_WORLD, ret, FUNC_NAME);

ompi/mpi/f77/info_get_nthkey_f.c

@@ -81,7 +81,6 @@ void mpi_info_get_nthkey_f(MPI_Fint *info, MPI_Fint *n, char *key,
 						OMPI_FINT_2_INT(*n),
 						c_key));
     
-    key_len = (key_len < MPI_MAX_INFO_KEY) ? key_len : MPI_MAX_INFO_KEY;
     if (OMPI_SUCCESS != (ret = ompi_fortran_string_c2f(c_key, key, key_len))) {
         c_err = OMPI_ERRHANDLER_INVOKE(MPI_COMM_WORLD, ret, FUNC_NAME);
         *ierr = OMPI_INT_2_FINT(c_err);

ompi/mpi/f77/strings.c

@@ -71,7 +71,18 @@ int ompi_fortran_string_f2c(char *fstr, int len, char **cstr)
 
 
 /*
- * copy a C string into a Fortran string
+ * Copy a C string into a Fortran string.  Note that when Fortran
+ * copies strings, even if it operates on subsets of the strings, it
+ * is expected to zero out the rest of the string with spaces.  Hence,
+ * when calling this function, the "len" parameter should be the
+ * compiler-passed length of the entire string, even if you're copying
+ * over less than the full string.  Specifically:
+ *
+ * http://www.ibiblio.org/pub/languages/fortran/ch2-13.html
+ *
+ * "Whole operations 'using' only 'part' of it, e.g. assignment of a
+ * shorter string, or reading a shorter record, automatically pads the
+ * rest of the string with blanks."
  */
 int ompi_fortran_string_c2f(char *cstr, char *fstr, int len)
 {