[gcc r11-9568] fortran: Fix deref of optional in gen. code. [PR100337, backport]

[Andre Vehreschild <vehre@gcc.gnu.org>]

https://gcc.gnu.org/g:ae57aae60d1be821feccb3160f8fdd5987ecba79

commit r11-9568-gae57aae60d1be821feccb3160f8fdd5987ecba79
Author: Andre Vehreschild <vehre@gcc.gnu.org>
Date:   Mon Feb 14 16:47:16 2022 +0100

    fortran: Fix deref of optional in gen. code. [PR100337, backport]
    
    gcc/fortran/ChangeLog:
    
            PR fortran/100337
            Backport from master.
            * trans-intrinsic.c (conv_co_collective): Check stat for null ptr
            before dereferrencing.
    
    gcc/testsuite/ChangeLog:
    
            PR fortran/100337
            * gfortran.dg/coarray_collectives_17.f90: New test.

Diff:
---
 gcc/fortran/trans-intrinsic.c                      | 24 +++++++++++--
 .../gfortran.dg/coarray_collectives_17.f90         | 42 ++++++++++++++++++++++
 2 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/gcc/fortran/trans-intrinsic.c b/gcc/fortran/trans-intrinsic.c
index eb928c6ef0a..bd6e6039429 100644
--- a/gcc/fortran/trans-intrinsic.c
+++ b/gcc/fortran/trans-intrinsic.c
@@ -11267,8 +11267,28 @@ conv_co_collective (gfc_code *code)
   if (flag_coarray == GFC_FCOARRAY_SINGLE)
     {
       if (stat != NULL_TREE)
-	gfc_add_modify (&block, stat,
-			fold_convert (TREE_TYPE (stat), integer_zero_node));
+	{
+	  /* For optional stats, check the pointer is valid before zero'ing.  */
+	  if (gfc_expr_attr (stat_expr).optional)
+	    {
+	      tree tmp;
+	      stmtblock_t ass_block;
+	      gfc_start_block (&ass_block);
+	      gfc_add_modify (&ass_block, stat,
+			      fold_convert (TREE_TYPE (stat),
+					    integer_zero_node));
+	      tmp = fold_build2 (NE_EXPR, logical_type_node,
+				 gfc_build_addr_expr (NULL_TREE, stat),
+				 null_pointer_node);
+	      tmp = fold_build3 (COND_EXPR, void_type_node, tmp,
+				 gfc_finish_block (&ass_block),
+				 build_empty_stmt (input_location));
+	      gfc_add_expr_to_block (&block, tmp);
+	    }
+	  else
+	    gfc_add_modify (&block, stat,
+			    fold_convert (TREE_TYPE (stat), integer_zero_node));
+	}
       return gfc_finish_block (&block);
     }
 
diff --git a/gcc/testsuite/gfortran.dg/coarray_collectives_17.f90 b/gcc/testsuite/gfortran.dg/coarray_collectives_17.f90
new file mode 100644
index 00000000000..84a6645865e
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/coarray_collectives_17.f90
@@ -0,0 +1,42 @@
+! { dg-do run }
+! { dg-options "-fcoarray=single" }
+!
+! PR 100337
+! Test case inspired by code submitted by Brad Richardson
+
+program main
+    implicit none
+
+    integer, parameter :: MESSAGE = 42
+    integer :: result
+
+    call myco_broadcast(MESSAGE, result, 1)
+
+    if (result /= MESSAGE) error stop 1
+contains
+    subroutine myco_broadcast(m, r, source_image, stat, errmsg)
+        integer, intent(in) :: m
+        integer, intent(out) :: r
+        integer, intent(in) :: source_image
+        integer, intent(out), optional :: stat
+        character(len=*), intent(inout), optional :: errmsg
+
+        integer :: data_length 
+
+        data_length = 1
+
+        call co_broadcast(data_length, source_image, stat, errmsg)
+
+        if (present(stat)) then
+            if (stat /= 0) return
+        end if
+
+        if (this_image() == source_image) then
+            r = m
+        end if
+
+        call co_broadcast(r, source_image, stat, errmsg)
+    end subroutine
+
+end program
+