From dfa2f821c18b7e926b5f5d6e394a0c915937db5e Mon Sep 17 00:00:00 2001
From: Jerry DeLisle <jvdelisle@gcc.gnu.org>
Date: Fri, 19 Feb 2021 12:47:54 -0800
Subject: [PATCH] fortran: Object types should be declared before use in
 NAMELIST.

gcc/fortran/ChangeLog:

	PR fortran/98686
	* match.c (gfc_match_namelist): If BT_UNKNOWN, check for
	IMPLICIT NONE and and issue an error, otherwise set the type
	to its IMPLICIT type so that any subsequent use of objects will
	will confirm their types.

gcc/testsuite/ChangeLog:

	PR fortran/98686
	* gfortran.dg/namelist_4.f90: Modify.
	* gfortran.dg/namelist_98.f90: New test.
---
 gcc/fortran/match.c                       | 18 ++++++++++++++++++
 gcc/testsuite/gfortran.dg/namelist_4.f90  |  7 ++++---
 gcc/testsuite/gfortran.dg/namelist_98.f90 | 11 +++++++++++
 3 files changed, 33 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/namelist_98.f90

diff --git a/gcc/fortran/match.c b/gcc/fortran/match.c
index 2df6191d7e6..4d5890fd523 100644
--- a/gcc/fortran/match.c
+++ b/gcc/fortran/match.c
@@ -5536,6 +5536,24 @@ gfc_match_namelist (void)
 	  if (m == MATCH_ERROR)
 	    goto error;
 
+	  if (sym->ts.type == BT_UNKNOWN)
+	    {
+	      if (gfc_current_ns->seen_implicit_none)
+		{
+		  /* It is required that members of a namelist be declared
+		     before the namelist.  We check this by checking if the
+		     symbol has a defined type for IMPLICIT NONE.  */
+		  gfc_error ("Symbol %qs in namelist %qs at %C must be "
+			     "declared before the namelist is declared.",
+			     sym->name, group_name->name);
+		  gfc_error_check ();
+		}
+	      else
+		/* If the type is not set already, we set it here to the
+		   implicit default type.  It is not allowed to set it
+		   later to any other type.  */
+		gfc_set_default_type (sym, 0, gfc_current_ns);
+	    }
 	  if (sym->attr.in_namelist == 0
 	      && !gfc_add_in_namelist (&sym->attr, sym->name, NULL))
 	    goto error;
diff --git a/gcc/testsuite/gfortran.dg/namelist_4.f90 b/gcc/testsuite/gfortran.dg/namelist_4.f90
index 538bceaa4b6..e6681fd3b55 100644
--- a/gcc/testsuite/gfortran.dg/namelist_4.f90
+++ b/gcc/testsuite/gfortran.dg/namelist_4.f90
@@ -23,12 +23,13 @@ CONTAINS
     G3=1
   END FUNCTION
 END module M1
- 
+
 program P1
+implicit none
 CONTAINS
 ! This has the additional wrinkle of a reference to the object.
   INTEGER FUNCTION F1()
-    NAMELIST /NML3/ F2 ! { dg-error "PROCEDURE attribute conflicts" }
+    NAMELIST /NML3/ F2 ! { dg-error "PROCEDURE attribute conflicts" }
 ! Used to ICE here
     f2 = 1             ! { dg-error "is not a VALUE" }
     F1=1
@@ -36,5 +37,5 @@ CONTAINS
   INTEGER FUNCTION F2()
     F2=1
   END FUNCTION
-END
+END
 
diff --git a/gcc/testsuite/gfortran.dg/namelist_98.f90 b/gcc/testsuite/gfortran.dg/namelist_98.f90
new file mode 100644
index 00000000000..19a7e869f92
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/namelist_98.f90
@@ -0,0 +1,11 @@
+! { dg-do compile }
+! pr98686
+  implicit none
+  real    :: x, m
+  namelist /NML/ x, m, q ! { dg-error "must be declared before the namelist*" }
+  integer :: q
+  x = 1.0
+  m = 2.0
+  q = 3
+  write(*, nml=NML)
+end
-- 
2.30.2