Fortran: fix for absent array argument passed to optional dummy [PR101135]

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 pattern.
	* gfortran.dg/ubsan/missing_optional_dummy_8.f90: New test.

gcc/fortran/trans-array.cc

@@ -7526,6 +7526,17 @@ 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.  Arguments of BIND(C)
+     procedures 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
+      && !is_CFI_desc (NULL, expr))
+    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);
 }
 

gcc/testsuite/gfortran.dg/missing_optional_dummy_6a.f90

@@ -49,7 +49,7 @@ 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" } }
 

gcc/testsuite/gfortran.dg/ubsan/missing_optional_dummy_8.f90

@@ -0,0 +1,108 @@
+! { 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 test_ar_wrapper
+  call test_ar_wrapper_c
+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)
+    call test1 (x)
+    call test_c (x)
+    call test1_c (x)
+  end subroutine test_wrapper
+
+  subroutine test_wrapper_c (w) bind(c)
+    real, dimension(1), intent(out), optional :: w
+    call test (w)
+    call test1 (w)
+    call test_c (w)
+    call test1_c (w)
+  end subroutine test_wrapper_c
+
+  subroutine test (y)
+    real, dimension(:), intent(out), optional :: y
+    if (present (y)) y=0.
+  end subroutine test
+
+  subroutine test_c (y) bind(c)
+    real, dimension(:), intent(out), optional :: y
+    if (present (y)) y=0.
+  end subroutine test_c
+
+  subroutine test1 (y)
+    real, dimension(1), intent(out), optional :: y
+    if (present (y)) y=0.
+  end subroutine test1
+
+  subroutine test1_c (y) bind(c)
+    real, dimension(1), intent(out), optional :: y
+    if (present (y)) y=0.
+  end subroutine test1_c
+
+  subroutine test_ar_wrapper (p, q, r)
+    real,               intent(out), optional :: p
+    real, dimension(1), intent(out), optional :: q
+    real, dimension(:), intent(out), optional :: r
+    call test_ar (p)
+    call test_ar (q)
+    call test_ar (r)
+    call test_ar_c (p)
+    call test_ar_c (q)
+    call test_ar_c (r)
+  end subroutine test_ar_wrapper
+
+  subroutine test_ar_wrapper_c (u, v, s) bind(c)
+    real,               intent(out), optional :: u
+    real, dimension(1), intent(out), optional :: v
+    real, dimension(:), intent(out), optional :: s
+    call test_ar (u)
+    call test_ar (v)
+!   call test_ar (s)    ! Disabled due to runtime segfault, see pr114355
+    call test_ar_c (u)
+    call test_ar_c (v)
+    call test_ar_c (s)
+  end subroutine test_ar_wrapper_c
+
+  subroutine test_ar (z)
+    real, dimension(..), intent(out), optional :: z
+  end subroutine test_ar
+
+  subroutine test_ar_c (z) bind(c)
+    real, dimension(..), intent(out), optional :: z
+  end subroutine test_ar_c
+end program
+
+! { dg-final { scan-tree-dump-times "data = v != 0B " 2 "original" } }
+! { dg-final { scan-tree-dump-times "data = w != 0B " 2 "original" } }
+! { dg-final { scan-tree-dump-times "data = q != 0B " 2 "original" } }
+! { dg-final { scan-tree-dump-times "data = x != 0B " 2 "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)" }"