From 46c72713f2e8a66782ba0d40c4d6bb3edc9aa382 Mon Sep 17 00:00:00 2001
From: dmitrykobets-msft <89153909+dmitrykobets-msft@users.noreply.github.com>
Date: Sat, 24 Dec 2022 11:49:26 -0800
Subject: [PATCH] Document potentially confusing behavior in gsl::narrow
 (#1073)

NaN != Nan, so the comparisons used in gsl::narrow will always throw when attempting to cast a NaN value. This may be surprising, so document it.
---
 include/gsl/narrow | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/gsl/narrow b/include/gsl/narrow
index 7578c8b..5c87087 100644
--- a/include/gsl/narrow
+++ b/include/gsl/narrow
@@ -52,6 +52,7 @@ GSL_SUPPRESS(p.2) // NO-FORMAT: attribute // don't rely on undefined behavior
     #pragma GCC diagnostic push
     #pragma GCC diagnostic ignored "-Wfloat-equal"
 #endif
+    // Note: NaN will always throw, since NaN != NaN
     if (static_cast<U>(t) != u || (is_different_signedness && ((t < T{}) != (u < U{}))))
     {
         throw narrowing_error{};