Re: [Patch, fortran] PR126909 - Lost statement label in a program with a CONTAINS section

From 3606368c76db6fe2a44376cee2d1aa40e80c529c Mon Sep 17 00:00:00 2001
From: Paul Thomas <[email protected]>
Date: Sat, 22 Aug 2026 09:37:05 +0100
Subject: [PATCH] Fortran: Lost statement label in a program with a CONTAINS
 section [PR126909]

2026-08-22  Paul Thomas  <[email protected]>

gcc/fortran
	PR fortran/126909
	* parse.cc (accept_statement): After a contains section, a new
	namespace is started and, without correction, the new statement
	the label, if there is one, would be stored there.Go back to
	the containing namespace and store it there. Likewise add the
	labelled return statement to the previous entry on the state
	stack.
gcc/testsuite
	PR fortran/126909
	* gfortran.dg/pr126909.f90: New test.
---
 gcc/fortran/parse.cc                   | 28 +++++++++-
 gcc/testsuite/gfortran.dg/pr126909.f90 | 77 ++++++++++++++++++++++++++
 2 files changed, 105 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/pr126909.f90

diff --git a/gcc/fortran/parse.cc b/gcc/fortran/parse.cc
index 47b443c4a5f..311dfedabce 100644
--- a/gcc/fortran/parse.cc
+++ b/gcc/fortran/parse.cc
@@ -3253,8 +3253,32 @@ accept_statement (gfc_statement st)
     case ST_END_SUBROUTINE:
       if (gfc_statement_label != NULL)
 	{
-	  new_st.op = EXEC_RETURN;
-	  add_statement ();
+	  /* After a contains section, a new namespace is started together with
+	     a new state_stack. The statement label must be attached to the
+	     previous state after finding the label in its namespace.  */
+	  if (gfc_state_stack->head == NULL
+	      && gfc_state_stack->previous
+	      && gfc_state_stack->previous->sym
+	      && gfc_state_stack->previous->sym->ns
+	      && gfc_state_stack->previous->sym->ns->parent == NULL)
+	    {
+	      int value = gfc_current_ns->st_labels->value;
+	      gfc_state_data *previous_state = gfc_state_stack;
+	      gfc_namespace *old_ns = gfc_current_ns;
+	      gfc_current_ns = gfc_state_stack->previous->sym->ns;
+	      new_st.here = gfc_get_st_label (value);
+	      new_st.here->defined = ST_LABEL_TARGET;
+	      new_st.op = EXEC_RETURN;
+	      gfc_state_stack = gfc_state_stack->previous;
+	      add_statement ();
+	      gfc_state_stack = previous_state;
+	      gfc_current_ns = old_ns;
+	    }
+	  else
+	   {
+	     new_st.op = EXEC_RETURN;
+	     add_statement ();
+	   }
 	}
       else
 	{
diff --git a/gcc/testsuite/gfortran.dg/pr126909.f90 b/gcc/testsuite/gfortran.dg/pr126909.f90
new file mode 100644
index 00000000000..bb95d9d7cdf
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr126909.f90
@@ -0,0 +1,77 @@
+! {dg-do run }
+! { dg-options "-fdump-tree-original" }
+!
+! Test the fix for PR126909, in which END PROGRAM/FUNCTION/SUBROUTINE labels
+! were not being generated correctly, when preceded by contain sections.
+!
+! Contributed by Steve Kargl  <[email protected]>
+!
+Module tally
+  integer :: ctr = 0
+contains
+  integer function two_power_n_plus (n, base)
+    integer, intent(IN) :: n, base
+    two_power_n_plus = 2**n  + base
+  end function two_power_n_plus
+end module
+
+program lost
+   use tally
+   interface
+      function yet_more_lost() result(i)
+         integer :: i
+      end function yet_more_lost
+   end interface
+
+   goto 9
+   stop 1
+9  ctr = two_power_n_plus (1, ctr)
+   call sub()
+   call more_lost()
+   if (yet_more_lost () /= 42) stop 2
+   if (ctr /= 126) stop 3
+   goto 10
+   stop 4
+   contains
+      subroutine sub()
+         ctr = two_power_n_plus (2, ctr)
+         goto 11
+         stop 5
+11    end subroutine sub
+10 end program lost
+
+subroutine more_lost
+   use tally
+   goto 9
+   stop 6
+9  ctr = two_power_n_plus (3, ctr)
+   call sub2()
+   goto 10
+   stop 7
+   contains
+      subroutine sub2()
+         ctr = two_power_n_plus (4, ctr)
+         goto 11
+         stop 8
+11    end subroutine sub2
+10 end subroutine more_lost
+
+function yet_more_lost() result(i)
+   use tally
+   integer :: i
+   i = 42
+   goto 9
+   stop 9
+9  ctr = two_power_n_plus (5, ctr)
+   call sub3()
+   goto 10
+   stop 10
+   contains
+      subroutine sub3()
+         ctr = two_power_n_plus (6, ctr)
+         goto 11
+         stop 11
+11    end subroutine sub3
+10 end function yet_more_lost
+
+! { dg-final { scan-tree-dump-times "label.000010" 6 "original" } }
-- 
2.55.0