From c15b386203af5d9f0553ceb1404780282a651271 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Antonio=20S=C3=A1nchez?= <cantonios@google.com>
Date: Tue, 14 Feb 2023 18:30:58 +0000
Subject: [PATCH] Fix MSVC atan2 test.

---
 test/array_cwise.cpp | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/test/array_cwise.cpp b/test/array_cwise.cpp
index 1e361aa29..b55723de4 100644
--- a/test/array_cwise.cpp
+++ b/test/array_cwise.cpp
@@ -100,7 +100,18 @@ void binary_ops_test() {
                          [](const auto& x, const auto& y) { return std::pow(x, y); });
   binary_op_test<Scalar>("atan2",
                          [](const auto& x, const auto& y) { return Eigen::atan2(x, y); },
-                         [](const auto& x, const auto& y) { return std::atan2(x, y); });
+                         [](const auto& x, const auto& y) {
+                            auto t = std::atan2(x, y);
+#if EIGEN_COMP_MSVC
+                            // Work around MSVC return value on underflow.
+                            // |atan(y/x)| is bounded above by |y/x|, so on underflow return y/x according to POSIX spec.
+                            // MSVC otherwise returns denorm_min.
+                            if (EIGEN_PREDICT_FALSE(std::abs(t) == std::numeric_limits<decltype(t)>::denorm_min())) {
+                              return x/y;
+                            }
+#endif
+                            return t;
+                          });
 }
 
 template <typename Scalar>