[PATCH] Fortran: fix treatment of character, value, optional dummy arguments [PR107444]

[Harald Anlauf <anlauf@gmx.de>]

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Dear Fortranners,

the attached patch is a follow-up to the fix for PR107441,
as it finally fixes the treatment of character dummy arguments
that have the value,optional attribute, and allows for checking
of the presence of such arguments.

This entails a small ABI clarification, as the previous text
was not really clear on the argument passing conventions,
and the previously generated code was inconsistent at best,
or rather wrong, for this kind of procedure arguments.
(E.g. the number of passed arguments was varying...)

Testcase cross-checked with NAG 7.1.

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

Thanks,
Harald


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From d87e299dd2b7f4be6ca829e80cd94babc53fa12f Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anlauf@gmx.de>
Date: Thu, 10 Nov 2022 22:30:27 +0100
Subject: [PATCH] Fortran: fix treatment of character, value, optional dummy
 arguments [PR107444]

Fix handling of character dummy arguments that have the optional+value
attribute.  Change name of internal symbols that carry the hidden presence
status of optional arguments to distinguish them from the internal hidden
character length.  Update documentation to clarify the gfortran ABI.

gcc/fortran/ChangeLog:

	PR fortran/107444
	* trans-decl.cc (create_function_arglist): Extend presence status
	to all intrinsic types, and change prefix of internal symbol to '.'.
	* trans-expr.cc (gfc_conv_expr_present): Align to changes in
	create_function_arglist.
	(gfc_conv_procedure_call): Fix generation of procedure arguments for
	the case of character dummy arguments with optional+value attribute.
	* trans-types.cc (gfc_get_function_type): Synchronize with changes
	to create_function_arglist.
	* doc/gfortran/naming-and-argument-passing-conventions.rst: Clarify
	the gfortran argument passing conventions with regard to OPTIONAL
	dummy arguments of intrinsic type.

gcc/testsuite/ChangeLog:

	PR fortran/107444
	* gfortran.dg/optional_absent_7.f90: Adjust regex.
	* gfortran.dg/optional_absent_8.f90: New test.
---
 ...aming-and-argument-passing-conventions.rst |  3 +-
 gcc/fortran/trans-decl.cc                     | 10 ++--
 gcc/fortran/trans-expr.cc                     | 25 ++++++---
 gcc/fortran/trans-types.cc                    | 14 ++---
 .../gfortran.dg/optional_absent_7.f90         |  2 +-
 .../gfortran.dg/optional_absent_8.f90         | 53 +++++++++++++++++++
 6 files changed, 84 insertions(+), 23 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/optional_absent_8.f90

diff --git a/gcc/fortran/doc/gfortran/naming-and-argument-passing-conventions.rst b/gcc/fortran/doc/gfortran/naming-and-argument-passing-conventions.rst
index 4baaee9bfec..fa999fac355 100644
--- a/gcc/fortran/doc/gfortran/naming-and-argument-passing-conventions.rst
+++ b/gcc/fortran/doc/gfortran/naming-and-argument-passing-conventions.rst
@@ -142,8 +142,7 @@ is used for dummy arguments; with ``VALUE``, those variables are
 passed by value.

 For ``OPTIONAL`` dummy arguments, an absent argument is denoted
-by a NULL pointer, except for scalar dummy arguments of type
-``INTEGER``, ``LOGICAL``, ``REAL`` and ``COMPLEX``
+by a NULL pointer, except for scalar dummy arguments of intrinsic type
 which have the ``VALUE`` attribute.  For those, a hidden Boolean
 argument (``logical(kind=C_bool),value``) is used to indicate
 whether the argument is present.
diff --git a/gcc/fortran/trans-decl.cc b/gcc/fortran/trans-decl.cc
index 94988b8690e..217de6b8da0 100644
--- a/gcc/fortran/trans-decl.cc
+++ b/gcc/fortran/trans-decl.cc
@@ -2708,16 +2708,16 @@ create_function_arglist (gfc_symbol * sym)
 		type = gfc_sym_type (f->sym);
 	    }
 	}
-      /* For noncharacter scalar intrinsic types, VALUE passes the value,
+      /* For scalar intrinsic types, VALUE passes the value,
 	 hence, the optional status cannot be transferred via a NULL pointer.
 	 Thus, we will use a hidden argument in that case.  */
-      else if (f->sym->attr.optional && f->sym->attr.value
-	       && !f->sym->attr.dimension && f->sym->ts.type != BT_CLASS
-	       && !gfc_bt_struct (f->sym->ts.type))
+      if (f->sym->attr.optional && f->sym->attr.value
+	  && !f->sym->attr.dimension && f->sym->ts.type != BT_CLASS
+	  && !gfc_bt_struct (f->sym->ts.type))
 	{
           tree tmp;
           strcpy (&name[1], f->sym->name);
-          name[0] = '_';
+	  name[0] = '.';
           tmp = build_decl (input_location,
 			    PARM_DECL, get_identifier (name),
 			    boolean_type_node);
diff --git a/gcc/fortran/trans-expr.cc b/gcc/fortran/trans-expr.cc
index f3fbb527157..b95c5cf2f96 100644
--- a/gcc/fortran/trans-expr.cc
+++ b/gcc/fortran/trans-expr.cc
@@ -1985,15 +1985,14 @@ gfc_conv_expr_present (gfc_symbol * sym, bool use_saved_desc)

   /* Intrinsic scalars with VALUE attribute which are passed by value
      use a hidden argument to denote the present status.  */
-  if (sym->attr.value && sym->ts.type != BT_CHARACTER
-      && sym->ts.type != BT_CLASS && sym->ts.type != BT_DERIVED
-      && !sym->attr.dimension)
+  if (sym->attr.value && !sym->attr.dimension
+      && sym->ts.type != BT_CLASS && !gfc_bt_struct (sym->ts.type))
     {
       char name[GFC_MAX_SYMBOL_LEN + 2];
       tree tree_name;

       gcc_assert (TREE_CODE (decl) == PARM_DECL);
-      name[0] = '_';
+      name[0] = '.';
       strcpy (&name[1], sym->name);
       tree_name = get_identifier (name);

@@ -6162,11 +6161,21 @@ gfc_conv_procedure_call (gfc_se * se, gfc_symbol * sym,
 		 value, pass "0" and a hidden argument gives the optional
 		 status.  */
 	      if (fsym && fsym->attr.optional && fsym->attr.value
-		  && !fsym->attr.dimension && fsym->ts.type != BT_CHARACTER
-		  && fsym->ts.type != BT_CLASS && fsym->ts.type != BT_DERIVED)
+		  && !fsym->attr.dimension && fsym->ts.type != BT_CLASS
+		  && !gfc_bt_struct (sym->ts.type))
 		{
-		  parmse.expr = fold_convert (gfc_sym_type (fsym),
-					      integer_zero_node);
+		  if (fsym->ts.type == BT_CHARACTER)
+		    {
+		      /* Pass a NULL pointer for an absent CHARACTER arg
+			 and a length of zero.  */
+		      parmse.expr = null_pointer_node;
+		      parmse.string_length
+			= build_int_cst (gfc_charlen_type_node,
+					 0);
+		    }
+		  else
+		    parmse.expr = fold_convert (gfc_sym_type (fsym),
+						integer_zero_node);
 		  vec_safe_push (optionalargs, boolean_false_node);
 		}
 	      else
diff --git a/gcc/fortran/trans-types.cc b/gcc/fortran/trans-types.cc
index 42907becd27..196f2cecbfc 100644
--- a/gcc/fortran/trans-types.cc
+++ b/gcc/fortran/trans-types.cc
@@ -3225,15 +3225,15 @@ gfc_get_function_type (gfc_symbol * sym, gfc_actual_arglist *actual_args,

 	  vec_safe_push (hidden_typelist, type);
 	}
-      /* For noncharacter scalar intrinsic types, VALUE passes the value,
+      /* For scalar intrinsic types, VALUE passes the value,
 	 hence, the optional status cannot be transferred via a NULL pointer.
 	 Thus, we will use a hidden argument in that case.  */
-      else if (arg
-	       && arg->attr.optional
-	       && arg->attr.value
-	       && !arg->attr.dimension
-	       && arg->ts.type != BT_CLASS
-	       && !gfc_bt_struct (arg->ts.type))
+      if (arg
+	  && arg->attr.optional
+	  && arg->attr.value
+	  && !arg->attr.dimension
+	  && arg->ts.type != BT_CLASS
+	  && !gfc_bt_struct (arg->ts.type))
 	vec_safe_push (typelist, boolean_type_node);
       /* Coarrays which are descriptorless or assumed-shape pass with
 	 -fcoarray=lib the token and the offset as hidden arguments.  */
diff --git a/gcc/testsuite/gfortran.dg/optional_absent_7.f90 b/gcc/testsuite/gfortran.dg/optional_absent_7.f90
index 1be981c88f6..163d0b67cb6 100644
--- a/gcc/testsuite/gfortran.dg/optional_absent_7.f90
+++ b/gcc/testsuite/gfortran.dg/optional_absent_7.f90
@@ -27,5 +27,5 @@ contains
   end subroutine s
 end program p

-! { dg-final { scan-tree-dump "void s .* c, .* o, logical.* _o, integer.* _c" "original" } }
+! { dg-final { scan-tree-dump "void s .* c, .* o, logical.* \.o, integer.* _c" "original" } }
 ! { dg-final { scan-tree-dump ", integer.*, logical.*, integer.* pp" "original" } }
diff --git a/gcc/testsuite/gfortran.dg/optional_absent_8.f90 b/gcc/testsuite/gfortran.dg/optional_absent_8.f90
new file mode 100644
index 00000000000..e3c04451f3b
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/optional_absent_8.f90
@@ -0,0 +1,53 @@
+! { dg-do run }
+! PR fortran/107444
+!
+! Check that procedures with optional arguments that have the value attribute
+! work for intrinsic types including character, and that the presence check
+! works.
+!
+! Co-contributed by M.Morin
+
+program p
+  implicit none
+  interface
+     subroutine i(c, o)
+       character(*) :: c
+       character(3), optional, value :: o
+     end subroutine i
+  end interface
+  procedure(i), pointer :: pp
+  call s([.false.,.false.,.false.],  0)
+  call s([.true., .false.,.false.], 10, i=7)
+  call s([.false.,.true. ,.false.], 20, c='abc')
+  call s([.false.,.false.,.true. ], 30, r=3.0)
+  pp => f
+  call pp ("abcd", "xyz")
+contains
+  subroutine s (expect,code,i,c,r)
+    logical, intent(in)           :: expect(:)
+    integer, intent(in)           :: code
+    integer     , value, optional :: i
+    character(3), value, optional :: c
+    real        , value, optional :: r
+    if (expect(1) .neqv. present (i)) stop 1+code
+    if (expect(2) .neqv. present (c)) stop 2+code
+    if (expect(3) .neqv. present (r)) stop 3+code
+    if (present (i)) then
+       if (i /= 7) stop 4+code
+    end if
+    if (present (c)) then
+       if (c /= "abc") stop 5+code
+    end if
+    if (present (r)) then
+       if (r /= 3.0) stop 6+code
+    end if
+  end subroutine s
+  subroutine f (c, o)
+    character(*) :: c
+    character(3), optional, value :: o
+    if (c /= "abcd") stop 41
+    if (len (c) /= 4) stop 42
+    if (.not. present (o)) stop 43
+    if (o /= "xyz")  stop 44
+  end subroutine f
+end
--
2.35.3