2 files changed, 47 insertions, 0 deletions
diff --git a/core/fxcrt/fx_extension.h b/core/fxcrt/fx_extension.h
index cef943fc99..dcdd64e1fc 100644
--- a/core/fxcrt/fx_extension.h
+++ b/core/fxcrt/fx_extension.h
@@ -8,6 +8,7 @@
 #define CORE_FXCRT_FX_EXTENSION_H_
 
 #include <cctype>
+#include <cmath>
 #include <cwctype>
 #include <memory>
 
@@ -92,4 +93,20 @@ void FXSYS_IntToFourHexChars(uint16_t c, char* buf);
 
 size_t FXSYS_ToUTF16BE(uint32_t unicode, char* buf);
 
+// Strict order over floating types where NaNs may be present.
+template <typename T>
+bool FXSYS_SafeEQ(const T& lhs, const T& rhs) {
+  return (std::isnan(lhs) && std::isnan(rhs)) ||
+         (!std::isnan(lhs) && !std::isnan(rhs) && lhs == rhs);
+}
+
+template <typename T>
+bool FXSYS_SafeLT(const T& lhs, const T& rhs) {
+  if (std::isnan(lhs) && std::isnan(rhs))
+    return false;
+  if (std::isnan(lhs) || std::isnan(rhs))
+    return std::isnan(lhs) < std::isnan(rhs);
+  return lhs < rhs;
+}
+
 #endif  // CORE_FXCRT_FX_EXTENSION_H_
diff --git a/core/fxcrt/fx_extension_unittest.cpp b/core/fxcrt/fx_extension_unittest.cpp
index 39f26b534b..d84071b83a 100644
--- a/core/fxcrt/fx_extension_unittest.cpp
+++ b/core/fxcrt/fx_extension_unittest.cpp
@@ -3,6 +3,9 @@
 // found in the LICENSE file.
 
 #include "core/fxcrt/fx_extension.h"
+
+#include <limits>
+
 #include "testing/gtest/include/gtest/gtest.h"
 
 TEST(fxcrt, FXSYS_HexCharToInt) {
@@ -134,3 +137,30 @@ TEST(fxcrt, FXSYS_wcstof) {
                   FXSYS_wcstof(L"99999999999999999", 17, &used_len));
   EXPECT_EQ(17, used_len);
 }
+
+TEST(fxcrt, FXSYS_SafeOps) {
+  const float fMin = std::numeric_limits<float>::min();
+  const float fMax = std::numeric_limits<float>::max();
+  const float fInf = std::numeric_limits<float>::infinity();
+  const float fNan = std::numeric_limits<float>::quiet_NaN();
+  const float ascending[] = {fMin, 1.0f, 2.0f, fMax, fInf, fNan};
+
+  for (size_t i = 0; i < FX_ArraySize(ascending); ++i) {
+    for (size_t j = 0; j < FX_ArraySize(ascending); ++j) {
+      if (i == j) {
+        EXPECT_TRUE(FXSYS_SafeEQ(ascending[i], ascending[j]))
+            << " at " << i << " " << j;
+      } else {
+        EXPECT_FALSE(FXSYS_SafeEQ(ascending[i], ascending[j]))
+            << " at " << i << " " << j;
+      }
+      if (i < j) {
+        EXPECT_TRUE(FXSYS_SafeLT(ascending[i], ascending[j]))
+            << " at " << i << " " << j;
+      } else {
+        EXPECT_FALSE(FXSYS_SafeLT(ascending[i], ascending[j]))
+            << " at " << i << " " << j;
+      }
+    }
+  }
+}