From f4486389b87b1758caffe4621ed45754e698fa47 Mon Sep 17 00:00:00 2001
From: Rian Quinn <rianquinn@gmail.com>
Date: Fri, 28 Oct 2016 00:45:54 -0600
Subject: [PATCH] Fix overflow found by GCC in
 basic_zstring_span::as_string_span().
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This patch fixes an overflow that was identified with
strict overflow warnings enabled, and optimizations
turned on

Signed-off-by: “Rian <“rianquinn@gmail.com”>
---
 gsl/string_span | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gsl/string_span b/gsl/string_span
index fb943dc..703bc01 100644
--- a/gsl/string_span
+++ b/gsl/string_span
@@ -554,7 +554,8 @@ public:
 
     constexpr string_span_type as_string_span() const noexcept
     {
-        return span_.first(span_.size() - 1);
+        auto sz = span_.size();
+        return span_.first(sz <= 0 ? 0 : sz - 1);
     }
 
     constexpr string_span_type ensure_z() const noexcept { return gsl::ensure_z(span_); }