[PATCH] Fortran : Runtime error, reshape constant array assignment, PR96624

[Mark Eggleston <mark.eggleston@codethink.co.uk>]

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Please find attached a fix for PR96624.  The original patch was by Steve 
Kargl.

Also occurs on releases/gcc-10, releases/gcc-9 and releases/gcc-8 branches.

OK to commit to master and backport?

[PATCH] Fortran  : Runtime error, reshape constant array assignment  PR96624

When assigning a reshaped constant array of shape [2,0] to a
variable fails with an invalid memory access.  If a varibale
with the parameter attribute is initialised with the same reshape
there is no runtime error.

2020-08-20  Steven G. Kargl  <kargl@gcc.gnu.org>

gcc/fortran/

     PR fortran/96624
     * simplify.c (gfc_simplifiy_reshape): Add new variable "zerosize".
     Set zerosize if any of the result shape ranks are zero.  After
     setting the result shapes, if zerosize is set jump to new label
     "sizezero".  Add label "sizezero" just before clearing index and
     returning result.

2020-08-20  Mark Eggleston <markeggleston@gcc.gnu.org>

gcc/testsuite/

     PR fortran/96624
     *gfortran/pr96624.f90: New test.

-- 
https://www.codethink.co.uk/privacy.html


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From ab94bb744a7d64751f6b93cc56ad3ed5fe5cfc81 Mon Sep 17 00:00:00 2001
From: Mark Eggleston <markeggleston@gcc.gnu.org>
Date: Mon, 17 Aug 2020 13:50:28 +0100
Subject: [PATCH] Fortran  : Runtime error, reshape constant array assignment
 PR96624

When assigning a reshaped constant array of shape [2,0] to a
variable fails with an invalid memory access.  If a varibale
with the parameter attribute is initialised with the same reshape
there is no runtime error.

2020-08-20  Steven G. Kargl  <kargl@gcc.gnu.org>

gcc/fortran/

	PR fortran/96624
	* simplify.c (gfc_simplifiy_reshape): Add new variable "zerosize".
	Set zerosize if any of the result shape ranks are zero.  After
	setting the result shapes, if zerosize is set jump to new label
	"sizezero".  Add label "sizezero" just before clearing index and
	returning result.

2020-08-20  Mark Eggleston  <markeggleston@gcc.gnu.org>

gcc/testsuite/

	PR fortran/96624
	*gfortran/pr96624.f90: New test.
---
 gcc/fortran/simplify.c                | 11 ++++++++++-
 gcc/testsuite/gfortran.dg/pr96624.f90 | 10 ++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gfortran.dg/pr96624.f90

diff --git a/gcc/fortran/simplify.c b/gcc/fortran/simplify.c
index eb8b2afeb29..0d77d289651 100644
--- a/gcc/fortran/simplify.c
+++ b/gcc/fortran/simplify.c
@@ -6721,6 +6721,7 @@ gfc_simplify_reshape (gfc_expr *source, gfc_expr *shape_exp,
   unsigned long j;
   size_t nsource;
   gfc_expr *e, *result;
+  bool zerosize = false;
 
   /* Check that argument expression types are OK.  */
   if (!is_constant_array_expr (source)
@@ -6843,7 +6844,14 @@ gfc_simplify_reshape (gfc_expr *source, gfc_expr *shape_exp,
   result->rank = rank;
   result->shape = gfc_get_shape (rank);
   for (i = 0; i < rank; i++)
-    mpz_init_set_ui (result->shape[i], shape[i]);
+    {
+      mpz_init_set_ui (result->shape[i], shape[i]);
+      if (shape[i] == 0)
+	zerosize = true;
+    }
+ 
+  if (zerosize)
+    goto sizezero;
 
   while (nsource > 0 || npad > 0)
     {
@@ -6893,6 +6901,7 @@ inc:
       break;
     }
 
+sizezero:
   mpz_clear (index);
 
   return result;
diff --git a/gcc/testsuite/gfortran.dg/pr96624.f90 b/gcc/testsuite/gfortran.dg/pr96624.f90
new file mode 100644
index 00000000000..a4cfe5c3279
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr96624.f90
@@ -0,0 +1,10 @@
+! { dg-do run }
+
+program test
+  integer :: a(2,0)
+  character(4) :: buffer
+  a = reshape([1,2,3,4], [2,0])
+  write(buffer,"(2a1)") ">", "<"
+  if (trim(buffer).ne."><") stop 1
+end
+
-- 
2.11.0