[PR fortran/71203, patch] - ICE on zero-length arrays or substrings

[Harald Anlauf]

The attached patch addresses ICEs on several situations with zero-length
arrays of strings or zero-length substrings, which were caused by a NULL
pointer dereference in those particular situations.

To the reviewer: I am not 100% sure that my solution is correct, but it
solves the issues reported and regtests cleanly on x86_64-pc-linux-gnu.

OK for trunk?  Backports?

Thanks,
Harald

P.S.: the PR has another ICE with integer array constructors which is
unrelated and under investigation.


2019-03-05  Harald Anlauf  <anlauf@gmx.de>

	PR fortran/71203
	* expr.c (simplify_const_ref): Avoid null pointer dereference.

2019-03-05  Harald Anlauf  <anlauf@gmx.de>

	PR fortran/71203
	* gfortran.dg/substr_8.f90: New test.

-------------- next part --------------
Index: gcc/fortran/expr.c
===================================================================
--- gcc/fortran/expr.c	(revision 269400)
+++ gcc/fortran/expr.c	(working copy)
@@ -1897,8 +1897,14 @@
 			string_len = 0;
 
 		      if (!p->ts.u.cl)
-			p->ts.u.cl = gfc_new_charlen (p->symtree->n.sym->ns,
-						      NULL);
+			{
+			  if (p->symtree)
+			    p->ts.u.cl = gfc_new_charlen (p->symtree->n.sym->ns,
+							  NULL);
+			  else
+			    p->ts.u.cl = gfc_new_charlen (gfc_current_ns,
+							  NULL);
+			}
 		      else
 			gfc_free_expr (p->ts.u.cl->length);
 
-------------- next part --------------
Index: gcc/testsuite/gfortran.dg/substr_8.f90
===================================================================
--- gcc/testsuite/gfortran.dg/substr_8.f90	(nonexistent)
+++ gcc/testsuite/gfortran.dg/substr_8.f90	(working copy)
@@ -0,0 +1,15 @@
+! { dg-do run }
+! PR fortran/71203 - used to ICE on zero-length arrays or substrings
+! Derived from original test cases by Gerhard Steinmetz
+
+program p
+  implicit none
+  character(3), parameter :: a(4) = ' '
+  character(*), parameter :: b(4) = 'abc'
+  character(*), parameter :: x(*) = a(2:2)(3:1)
+  character(*), parameter :: y(*) = a(2:1)(3:1)
+  character(*), parameter :: z(*) = b(2:1)(2:3)
+  if (size (x) /= 1 .or. len(x) /= 0) stop 1
+  if (size (y) /= 0 .or. len(y) /= 0) stop 2
+  if (size (z) /= 0 .or. len(z) /= 2) stop 3
+end