From 69ca8f83149107f48b86360eb878d9d746b99234 Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anlauf@gmx.de>
Date: Sat, 29 Jan 2022 22:18:30 +0100
Subject: [PATCH] Fortran: fix handling of absent array argument passed to
 optional dummy

gcc/fortran/ChangeLog:

	PR fortran/101135
	* trans-array.cc (gfc_get_dataptr_offset): Check for optional
	arguments being present before dereferencing data pointer.

gcc/testsuite/ChangeLog:

	PR fortran/101135
	* gfortran.dg/missing_optional_dummy_6a.f90: Adjust diagnostic patterns.
	* gfortran.dg/asan/missing_optional_dummy_7.f90: New test.
---
 gcc/fortran/trans-array.cc                    | 11 ++++
 .../asan/missing_optional_dummy_7.f90         | 64 +++++++++++++++++++
 .../gfortran.dg/missing_optional_dummy_6a.f90 |  4 +-
 3 files changed, 77 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/asan/missing_optional_dummy_7.f90

diff --git a/gcc/fortran/trans-array.cc b/gcc/fortran/trans-array.cc
index cfb6eac11c7..9eaa99c5550 100644
--- a/gcc/fortran/trans-array.cc
+++ b/gcc/fortran/trans-array.cc
@@ -7207,6 +7207,17 @@ gfc_get_dataptr_offset (stmtblock_t *block, tree parm, tree desc, tree offset,

   /* Set the target data pointer.  */
   offset = gfc_build_addr_expr (gfc_array_dataptr_type (desc), tmp);
+
+  /* Check for optional dummy argument being present.  BIND(C) procedure
+     arguments are excepted here since they are handled differently.  */
+  if (expr->expr_type == EXPR_VARIABLE
+      && expr->symtree->n.sym->attr.dummy
+      && expr->symtree->n.sym->attr.optional
+      && !expr->symtree->n.sym->ns->proc_name->attr.is_bind_c)
+    offset = build3_loc (input_location, COND_EXPR, TREE_TYPE (offset),
+			 gfc_conv_expr_present (expr->symtree->n.sym), offset,
+			 fold_convert (TREE_TYPE (offset), gfc_index_zero_node));
+
   gfc_conv_descriptor_data_set (block, parm, offset);
 }

diff --git a/gcc/testsuite/gfortran.dg/asan/missing_optional_dummy_7.f90 b/gcc/testsuite/gfortran.dg/asan/missing_optional_dummy_7.f90
new file mode 100644
index 00000000000..bdd7006170d
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/asan/missing_optional_dummy_7.f90
@@ -0,0 +1,64 @@
+! { dg-do run }
+! { dg-additional-options "-fdump-tree-original -fsanitize=undefined" }
+!
+! PR fortran/101135 - Load of null pointer when passing absent
+! assumed-shape array argument for an optional dummy argument
+!
+! Based on testcase by Marcel Jacobse
+
+program main
+  implicit none
+  character(len=3) :: a(6) = ['abc', 'def', 'ghi', 'jlm', 'nop', 'qrs']
+  call as ()
+  call as (a(::2))
+  call as_c ()
+  call as_c (a(2::2))
+  call test_wrapper
+  call test_wrapper_c
+  call test2_wrapper
+contains
+  subroutine as (xx)
+    character(len=*), optional, intent(in) :: xx(*)
+    if (.not. present (xx)) return
+    print *, xx(1:3)
+  end subroutine as
+  subroutine as_c (zz) bind(c)
+    character(len=*), optional, intent(in) :: zz(*)
+    if (.not. present (zz)) return
+    print *, zz(1:3)
+  end subroutine as_c
+
+  subroutine test_wrapper (x)
+    real, dimension(1), intent(out), optional :: x
+    call test (x) !
+  end subroutine test_wrapper
+  subroutine test (y)
+    real, dimension(:), intent(out), optional :: y
+    if (present (y)) y=0
+  end subroutine test
+
+  subroutine test_wrapper_c (w) bind(c)
+    real, dimension(1), intent(out), optional :: w
+    call test_c (w)
+  end subroutine test_wrapper_c
+  subroutine test_c (y) bind(c)
+    real, dimension(:), intent(out), optional :: y
+    if (present (y)) y=0
+  end subroutine test_c
+
+  subroutine test2_wrapper (u, v)
+    real,               intent(out), optional :: u
+    real, dimension(1), intent(out), optional :: v
+    call test2 (u)
+    call test2 (v) !
+  end subroutine test2_wrapper
+  subroutine test2 (z)
+    real, dimension(..), intent(out), optional :: z
+  end subroutine test2
+end program
+
+! { dg-final { scan-tree-dump-times "data = v != 0B " 1 "original" } }
+! { dg-final { scan-tree-dump-times "data = x != 0B " 1 "original" } }
+! { dg-final { scan-tree-dump-times "data = xx.0 != 0B " 1 "original" } }
+! { dg-output " abcghinop(\n|\r\n|\r)" }"
+! { dg-output " defjlmqrs(\n|\r\n|\r)" }"
diff --git a/gcc/testsuite/gfortran.dg/missing_optional_dummy_6a.f90 b/gcc/testsuite/gfortran.dg/missing_optional_dummy_6a.f90
index c08c97a2c7e..bd34613c143 100644
--- a/gcc/testsuite/gfortran.dg/missing_optional_dummy_6a.f90
+++ b/gcc/testsuite/gfortran.dg/missing_optional_dummy_6a.f90
@@ -49,10 +49,10 @@ end program test

 ! { dg-final { scan-tree-dump-times "scalar2 \\(slr1" 1 "original" } }

-! { dg-final { scan-tree-dump-times "= es1 != 0B" 1 "original" } }
+! { dg-final { scan-tree-dump-times "= es1 != 0B" 2 "original" } }
 ! { dg-final { scan-tree-dump-times "assumed_shape2 \\(es1" 0 "original" } }
 ! { dg-final { scan-tree-dump-times "explicit_shape2 \\(es1" 1 "original" } }

-! { dg-final { scan-tree-dump-times "= as1.0 != 0B" 2 "original" } }
+! { dg-final { scan-tree-dump-times "= as1.0 != 0B" 4 "original" } }
 ! { dg-final { scan-tree-dump-times "assumed_shape2 \\(as1" 0 "original" } }
 ! { dg-final { scan-tree-dump-times "explicit_shape2 \\(as1" 0 "original" } }
--
2.31.1