From 8ce1c8e7d0390361a1507000b7abbf6509b2fee9 Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anlauf@gmx.de>
Date: Mon, 27 Nov 2023 20:19:11 +0100
Subject: [PATCH] Fortran: deferred-length character optional dummy arguments
 [PR93762,PR100651]

gcc/fortran/ChangeLog:

	PR fortran/93762
	PR fortran/100651
	* trans-expr.cc (gfc_conv_missing_dummy): The character length for
	deferred-length dummy arguments is passed by reference, so that its
	value can be returned.  Adjust handling for optional dummies.

gcc/testsuite/ChangeLog:

	PR fortran/93762
	PR fortran/100651
	* gfortran.dg/optional_deferred_char_1.f90: New test.
---
 gcc/fortran/trans-expr.cc                     |  22 +++-
 .../gfortran.dg/optional_deferred_char_1.f90  | 100 ++++++++++++++++++
 2 files changed, 118 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/optional_deferred_char_1.f90

diff --git a/gcc/fortran/trans-expr.cc b/gcc/fortran/trans-expr.cc
index 50c4604a025..e992f60d8bb 100644
--- a/gcc/fortran/trans-expr.cc
+++ b/gcc/fortran/trans-expr.cc
@@ -2116,10 +2116,24 @@ gfc_conv_missing_dummy (gfc_se * se, gfc_expr * arg, gfc_typespec ts, int kind)

   if (ts.type == BT_CHARACTER)
     {
-      tmp = build_int_cst (gfc_charlen_type_node, 0);
-      tmp = fold_build3_loc (input_location, COND_EXPR, gfc_charlen_type_node,
-			     present, se->string_length, tmp);
-      tmp = gfc_evaluate_now (tmp, &se->pre);
+      /* Handle deferred-length dummies that pass the character length by
+	 reference so that the value can be returned.  */
+      if (ts.deferred && INDIRECT_REF_P (se->string_length))
+	{
+	  tmp = gfc_build_addr_expr (NULL_TREE, se->string_length);
+	  tmp = fold_build3_loc (input_location, COND_EXPR, TREE_TYPE (tmp),
+				 present, tmp, null_pointer_node);
+	  tmp = gfc_evaluate_now (tmp, &se->pre);
+	  tmp = build_fold_indirect_ref_loc (input_location, tmp);
+	}
+      else
+	{
+	  tmp = build_int_cst (gfc_charlen_type_node, 0);
+	  tmp = fold_build3_loc (input_location, COND_EXPR,
+				 gfc_charlen_type_node,
+				 present, se->string_length, tmp);
+	  tmp = gfc_evaluate_now (tmp, &se->pre);
+	}
       se->string_length = tmp;
     }
   return;
diff --git a/gcc/testsuite/gfortran.dg/optional_deferred_char_1.f90 b/gcc/testsuite/gfortran.dg/optional_deferred_char_1.f90
new file mode 100644
index 00000000000..d399dd11ca2
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/optional_deferred_char_1.f90
@@ -0,0 +1,100 @@
+! { dg-do run }
+! PR fortran/93762
+! PR fortran/100651 - deferred-length character as optional dummy argument
+
+program main
+  implicit none
+  character(:), allocatable :: err_msg, msg3(:)
+  character(:), pointer     :: err_msg2 => NULL()
+
+  ! Subroutines with optional arguments
+  call to_int ()
+  call to_int_p ()
+  call test_rank1 ()
+  call assert_code ()
+  call assert_p ()
+  call assert_rank1 ()
+
+  ! Test passing of optional arguments
+  call to_int (err_msg)
+  if (.not. allocated (err_msg)) stop 1
+  if (len (err_msg) /= 7)        stop 2
+  if (err_msg(1:7) /= "foo bar") stop 3
+
+  call to_int2 (err_msg)
+  if (.not. allocated (err_msg)) stop 4
+  if (len (err_msg) /= 7)        stop 5
+  if (err_msg(1:7) /= "foo bar") stop 6
+  deallocate (err_msg)
+
+  call to_int_p (err_msg2)
+  if (.not. associated (err_msg2)) stop 11
+  if (len (err_msg2) /= 8)         stop 12
+  if (err_msg2(1:8) /= "poo bla ") stop 13
+  deallocate (err_msg2)
+
+  call to_int2_p (err_msg2)
+  if (.not. associated (err_msg2)) stop 14
+  if (len (err_msg2) /= 8)         stop 15
+  if (err_msg2(1:8) /= "poo bla ") stop 16
+  deallocate (err_msg2)
+
+  call test_rank1 (msg3)
+  if (.not. allocated (msg3)) stop 21
+  if (len (msg3) /= 2)        stop 22
+  if (size (msg3) /= 42)      stop 23
+  if (any (msg3 /= "ok"))     stop 24
+  deallocate (msg3)
+
+contains
+
+  ! Deferred-length character, allocatable:
+  subroutine assert_code (err_msg0)
+    character(:), optional, allocatable :: err_msg0
+    if (present (err_msg0)) err_msg0 = 'foo bar'
+  end
+  ! Test: optional argument
+  subroutine to_int (err_msg1)
+    character(:), optional, allocatable :: err_msg1
+    call assert_code (err_msg1)
+  end
+  ! Control: non-optional argument
+  subroutine to_int2 (err_msg2)
+    character(:), allocatable :: err_msg2
+    call assert_code (err_msg2)
+  end
+
+  ! Rank-1:
+  subroutine assert_rank1 (msg)
+    character(:), optional, allocatable, intent(out) :: msg(:)
+    if (present (msg)) then
+       allocate (character(2) :: msg(42))
+       msg(:) = "ok"
+    end if
+  end
+
+  subroutine test_rank1 (msg1)
+    character(:), optional, allocatable, intent(out) :: msg1(:)
+    call assert_rank1 (msg1)
+  end
+
+  ! Deferred-length character, pointer:
+  subroutine assert_p (err_msg0)
+    character(:), optional, pointer :: err_msg0
+    if (present (err_msg0)) then
+       if (associated (err_msg0)) deallocate (err_msg0)
+       allocate (character(8) :: err_msg0)
+       err_msg0 = 'poo bla'
+    end if
+  end
+
+  subroutine to_int_p (err_msg1)
+    character(:), optional, pointer :: err_msg1
+    call assert_p (err_msg1)
+  end
+
+  subroutine to_int2_p (err_msg2)
+    character(:), pointer :: err_msg2
+    call assert_p (err_msg2)
+  end
+end
--
2.35.3