[PATCH] Fortran: deferred-length character optional dummy arguments [PR93762,PR100651]

[Harald Anlauf <anlauf@gmx.de>]

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Dear all,

the attached patch fixes the passing of deferred-length character
to optional dummy arguments: the character length shall be passed
by reference, not by value.

Original analysis of the issue by Steve in PR93762, independently
done by FX in PR100651.  The patch fixes both PRs.

Regtested on x86_64-pc-linux-gnu.  OK for mainline?

As the fix is local and affects only deferred-length character,
would it be ok to backport to 13-branch?

Thanks,
Harald


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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