From 5dd0cef67cff75cce292f2d17a0f048084a54512 Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <ian@gcc.gnu.org>
Date: Thu, 12 Dec 2013 21:03:10 +0000
Subject: compiler: Check for nil when slicing pointer to array.

From-SVN: r205942
---
 gcc/go/gofrontend/expressions.cc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/gcc/go/gofrontend/expressions.cc b/gcc/go/gofrontend/expressions.cc
index a5a056b..35bcdbb 100644
--- a/gcc/go/gofrontend/expressions.cc
+++ b/gcc/go/gofrontend/expressions.cc
@@ -10259,6 +10259,14 @@ Index_expression::do_lower(Gogo*, Named_object*, Statement_inserter*, int)
     {
       Expression* deref = Expression::make_unary(OPERATOR_MULT, left,
 						 location);
+
+      // For an ordinary index into the array, the pointer will be
+      // dereferenced.  For a slice it will not--the resulting slice
+      // will simply reuse the pointer, which is incorrect if that
+      // pointer is nil.
+      if (end != NULL || cap != NULL)
+	deref->issue_nil_check();
+
       return Expression::make_array_index(deref, start, end, cap, location);
     }
   else if (type->is_string_type())
-- 
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