[PATCH] Fortran: do not evaluate polymorphic functions twice in assignment [PR114012]

[Harald Anlauf <anlauf@gmx.de>]

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Dear all,

the attached simple patch fixes an issue where we evaluated
polymorphic functions twice in assignments: once for the _data
component, and once for the _vptr.  Using save_expr prevents
the double evaluation.

Regtested on x86_64-pc-linux-gnu.  OK for mainline?
And a backport to 13-branch after some delay?

Thanks,
Harald


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From 7a16143448ee21b716b54a94f83f9ee477af1b63 Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anlauf@gmx.de>
Date: Sun, 25 Feb 2024 21:18:23 +0100
Subject: [PATCH] Fortran: do not evaluate polymorphic functions twice in
 assignment [PR114012]

	PR fortran/114012

gcc/fortran/ChangeLog:

	* trans-expr.cc (gfc_conv_procedure_call): Evaluate non-trivial
	arguments just once before assigning to an unlimited polymorphic
	dummy variable.

gcc/testsuite/ChangeLog:

	* gfortran.dg/pr114012.f90: New test.
---
 gcc/fortran/trans-expr.cc              |  4 ++
 gcc/testsuite/gfortran.dg/pr114012.f90 | 81 ++++++++++++++++++++++++++
 2 files changed, 85 insertions(+)
 create mode 100644 gcc/testsuite/gfortran.dg/pr114012.f90

diff --git a/gcc/fortran/trans-expr.cc b/gcc/fortran/trans-expr.cc
index 118dfd7c9b2..d63c304661a 100644
--- a/gcc/fortran/trans-expr.cc
+++ b/gcc/fortran/trans-expr.cc
@@ -6691,6 +6691,10 @@ gfc_conv_procedure_call (gfc_se * se, gfc_symbol * sym,
 			    {
 			      tree efield;

+			      /* Evaluate arguments just once.  */
+			      if (e->expr_type != EXPR_VARIABLE)
+				parmse.expr = save_expr (parmse.expr);
+
 			      /* Set the _data field.  */
 			      tmp = gfc_class_data_get (var);
 			      efield = fold_convert (TREE_TYPE (tmp),
diff --git a/gcc/testsuite/gfortran.dg/pr114012.f90 b/gcc/testsuite/gfortran.dg/pr114012.f90
new file mode 100644
index 00000000000..9dbb031c664
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr114012.f90
@@ -0,0 +1,81 @@
+! { dg-do run }
+! PR fortran/114012
+!
+! Polymorphic functions were evaluated twice in assignment
+
+program test
+  implicit none
+
+  type :: custom_int
+     integer :: val = 2
+  end type
+
+  interface assignment(=)
+     procedure assign
+  end interface
+  interface operator(-)
+     procedure neg
+  end interface
+
+  type(custom_int) :: i
+  integer          :: count_assign, count_neg
+
+  count_assign = 0
+  count_neg    = 0
+
+  i = 1
+  if (count_assign /= 1 .or. count_neg /= 0) stop 1
+
+  i = -i
+  if (count_assign /= 2 .or. count_neg /= 1) stop 2
+  if (i% val /= -1) stop 3
+
+  i = neg(i)
+  if (count_assign /= 3 .or. count_neg /= 2) stop 4
+  if (i% val /=  1) stop 5
+
+  i = (neg(i))
+  if (count_assign /= 4 .or. count_neg /= 3) stop 6
+  if (i% val /= -1) stop 7
+
+  i = - neg(i)
+  if (count_assign /= 5 .or. count_neg /= 5) stop 8
+  if (i% val /= -1) stop 9
+
+contains
+
+  subroutine assign (field, val)
+    type(custom_int), intent(out) :: field
+    class(*), intent(in) :: val
+
+    count_assign = count_assign + 1
+
+    select type (val)
+    type is (integer)
+!      print *, " in assign(integer)", field%val, val
+       field%val = val
+    type is (custom_int)
+!      print *, " in assign(custom)", field%val, val%val
+       field%val = val%val
+    class default
+       error stop
+    end select
+
+  end subroutine assign
+
+  function neg (input_field) result(output_field)
+    type(custom_int), intent(in), target :: input_field
+    class(custom_int), allocatable :: output_field
+    allocate (custom_int :: output_field)
+
+    count_neg = count_neg + 1
+
+    select type (output_field)
+    type is (custom_int)
+!      print *, " in neg", output_field%val, input_field%val
+       output_field%val = -input_field%val
+    class default
+       error stop
+    end select
+  end function neg
+end program test
--
2.35.3