[Bug libfortran/95195] gfortran poorly handles a program error of writing a namelist to an unformatted file.

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95195

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|fortran                     |libfortran
           Priority|P3                          |P4

--- Comment #2 from anlauf at gcc dot gnu.org ---
The following patch generates a runtime error for namelist read:

diff --git a/libgfortran/io/list_read.c b/libgfortran/io/list_read.c
index 77d61421a0f..28744d21143 100644
--- a/libgfortran/io/list_read.c
+++ b/libgfortran/io/list_read.c
@@ -3549,6 +3549,14 @@ namelist_read (st_parameter_dt *dtp)
      name.  */
   namelist_info *prev_nl = NULL;

+  if (dtp->u.p.current_unit->flags.form == FORM_UNFORMATTED)
+    {
+      generate_error (&dtp->common, LIBERROR_OPTION_CONFLICT,
+                     "Namelist formatting not allowed for unit connected "
+                     "with FORM='UNFORMATTED'");
+      return;
+    }
+
   dtp->u.p.input_complete = 0;
   dtp->u.p.expanded_read = 0;

This generates:

At line 10 of file pr95195.f90 (unit = 10, file = 'test.dat')
Fortran runtime error: Namelist formatting not allowed for unit connected with
FORM='UNFORMATTED'

Error termination. Backtrace:
#0  0x7f80d510f1a7 in finalize_transfer
        at ../../../gcc-trunk/libgfortran/io/transfer.c:4128
#1  0x400b3b in test
        at /home/anlauf/gcc-bugs/pr95195.f90:10
#2  0x400b9c in main
        at /home/anlauf/gcc-bugs/pr95195.f90:12


Regtests cleanly for me.

Similar checks can be added for namelist write, list-directed formatting,
and non-advancing data transfers.  (F2018: 12.3.3.3)

Does this look better?