[PATCH] Fortran: initialize non-saved pointers with -fcheck=pointer [PR48958]

[Harald Anlauf]

Dear all,

the attached simple patch addresses a small, left-over issue in the
above PR and was already OK'ed in the PR by Thomas.  With it we
initialize the data component of a non-saved pointer variable when
-fcheck=pointer is specified, so that subsequent pointer checks
(e.g. for the SIZE intrinsic) trigger consistently and not randomly.

I plan to commit within 24h unless there are comments.

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

Thanks,
Harald


From eca02da7cfa3781727dfd1a0914b7d9d377b1511 Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anl...@gmx.de>
Date: Thu, 20 Feb 2025 21:03:12 +0100
Subject: [PATCH] Fortran: initialize non-saved pointers with -fcheck=pointer
 [PR48958]

	PR fortran/48958

gcc/fortran/ChangeLog:

	* trans-array.cc (gfc_trans_deferred_array): Initialized the data
	component of non-saved pointers when -fcheck=pointer is set.

gcc/testsuite/ChangeLog:

	* gfortran.dg/pointer_init_13.f90: New test.
---
 gcc/fortran/trans-array.cc                    |  7 ++++--
 gcc/testsuite/gfortran.dg/pointer_init_13.f90 | 24 +++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/pointer_init_13.f90

diff --git a/gcc/fortran/trans-array.cc b/gcc/fortran/trans-array.cc
index ec627dddffd..27378c432f7 100644
--- a/gcc/fortran/trans-array.cc
+++ b/gcc/fortran/trans-array.cc
@@ -12122,8 +12122,11 @@ gfc_trans_deferred_array (gfc_symbol * sym, gfc_wrapped_block * block)
       type = TREE_TYPE (descriptor);
     }
 
-  /* NULLIFY the data pointer, for non-saved allocatables.  */
-  if (GFC_DESCRIPTOR_TYPE_P (type) && !sym->attr.save && sym->attr.allocatable)
+  /* NULLIFY the data pointer for non-saved allocatables, or for non-saved
+     pointers when -fcheck=pointer is specified.  */
+  if (GFC_DESCRIPTOR_TYPE_P (type) && !sym->attr.save
+      && (sym->attr.allocatable
+	  || (sym->attr.pointer && (gfc_option.rtcheck & GFC_RTCHECK_POINTER))))
     {
       gfc_conv_descriptor_data_set (&init, descriptor, null_pointer_node);
       if (flag_coarray == GFC_FCOARRAY_LIB && sym->attr.codimension)
diff --git a/gcc/testsuite/gfortran.dg/pointer_init_13.f90 b/gcc/testsuite/gfortran.dg/pointer_init_13.f90
new file mode 100644
index 00000000000..ece423a9db6
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pointer_init_13.f90
@@ -0,0 +1,24 @@
+! { dg-do compile }
+! { dg-options "-fcheck=pointer -fdump-tree-optimized -O -fno-inline" }
+!
+! PR fortran/48958
+!
+! Initialize non-saved pointers with -fcheck=pointer to support runtime checks
+! of uses of possibly undefined pointers
+
+program p
+  implicit none
+  call s
+contains
+  subroutine s
+    integer, pointer :: a(:)
+    integer, pointer :: b(:) => NULL()
+    if (size (a) /= 0) stop 1
+    if (size (b) /= 0) stop 2
+    print *, size (a)
+    print *, size (b)
+  end
+end
+
+! { dg-final { scan-tree-dump-times "_gfortran_runtime_error_at" 1 "optimized" } }
+! { dg-final { scan-tree-dump-not "_gfortran_stop_numeric" "optimized" } }
-- 
2.43.0