Add std::isnan polyfill, fixing compilation under Embarcadero

Fixes #1438

include/internal/catch_compiler_capabilities.h

@@ -157,6 +157,12 @@
 #  define CATCH_INTERNAL_CONFIG_NO_WCHAR
 #endif // __DJGPP__
 
+////////////////////////////////////////////////////////////////////////////////
+// Embarcadero C++Build
+#if defined(__BORLANDC__)
+    #define CATCH_INTERNAL_CONFIG_POLYFILL_ISNAN
+#endif
+
 ////////////////////////////////////////////////////////////////////////////////
 
 // Use of __COUNTER__ is suppressed during code analysis in
@@ -238,6 +244,10 @@
 #  define CATCH_CONFIG_DISABLE_EXCEPTIONS
 #endif
 
+#if defined(CATCH_INTERNAL_CONFIG_POLYFILL_ISNAN) && !defined(CATCH_CONFIG_NO_POLYFILL_ISNAN) && !defined(CATCH_CONFIG_POLYFILL_ISNAN)
+#  define CATCH_CONFIG_POLYFILL_ISNAN
+#endif
+
 #if !defined(CATCH_INTERNAL_SUPPRESS_PARENTHESES_WARNINGS)
 #   define CATCH_INTERNAL_SUPPRESS_PARENTHESES_WARNINGS
 #   define CATCH_INTERNAL_UNSUPPRESS_PARENTHESES_WARNINGS

include/internal/catch_matchers_floating.cpp

@@ -7,6 +7,7 @@
 
 #include "catch_matchers_floating.h"
 #include "catch_enforce.h"
+#include "catch_polyfills.hpp"
 #include "catch_to_string.hpp"
 #include "catch_tostring.h"
 
@@ -57,7 +58,7 @@ template <typename FP>
 bool almostEqualUlps(FP lhs, FP rhs, int maxUlpDiff) {
     // Comparison with NaN should always be false.
     // This way we can rule it out before getting into the ugly details
-    if (std::isnan(lhs) || std::isnan(rhs)) {
+    if (Catch::isnan(lhs) || Catch::isnan(rhs)) {
         return false;
     }
 

include/internal/catch_polyfills.cpp

@@ -0,0 +1,31 @@
+/*
+ *  Created by Martin on 17/11/2017.
+ *
+ *  Distributed under the Boost Software License, Version 1.0. (See accompanying
+ *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#include "catch_polyfills.hpp"
+
+#include <cmath>
+
+namespace Catch {
+
+#if !defined(CATCH_CONFIG_POLYFILL_ISNAN)
+    bool isnan(float f) {
+        return std::isnan(f);
+    }
+    bool isnan(double d) {
+        return std::isnan(d);
+    }
+#else
+    // For now we only use this for embarcadero
+    bool isnan(float f) {
+        return std::_isnan(f);
+    }
+    bool isnan(double d) {
+        return std::_isnan(d);
+    }
+#endif
+
+} // end namespace Catch

include/internal/catch_polyfills.hpp

@@ -0,0 +1,15 @@
+/*
+ *  Created by Martin on 17/11/2017.
+ *
+ *  Distributed under the Boost Software License, Version 1.0. (See accompanying
+ *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+#ifndef TWOBLUECUBES_CATCH_POLYFILLS_HPP_INCLUDED
+#define TWOBLUECUBES_CATCH_POLYFILLS_HPP_INCLUDED
+
+namespace Catch {
+    bool isnan(float f);
+    bool isnan(double d);
+}
+
+#endif // TWOBLUECUBES_CATCH_POLYFILLS_HPP_INCLUDED

include/internal/catch_tostring.cpp

@@ -20,6 +20,7 @@
 #include "catch_tostring.h"
 #include "catch_interfaces_config.h"
 #include "catch_context.h"
+#include "catch_polyfills.hpp"
 
 #include <cmath>
 #include <iomanip>
@@ -68,7 +69,7 @@ namespace Detail {
 
 template<typename T>
 std::string fpToString( T value, int precision ) {
-    if (std::isnan(value)) {
+    if (Catch::isnan(value)) {
         return "nan";
     }