From 059d82014ec912fe0d63f48caee5e1a53e405201 Mon Sep 17 00:00:00 2001
From: Martin Taibr <taibr.martin@gmail.com>
Date: Fri, 16 Nov 2018 10:57:30 +0100
Subject: [PATCH] document isnan

---
 qcsrc/lib/deglobalization.qh  | 12 ------------
 qcsrc/lib/float.qh            |  1 +
 qcsrc/lib/warpzone/mathlib.qc | 10 ++++++++--
 3 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/qcsrc/lib/deglobalization.qh b/qcsrc/lib/deglobalization.qh
index 315ff6d6a..21f303a3e 100644
--- a/qcsrc/lib/deglobalization.qh
+++ b/qcsrc/lib/deglobalization.qh
@@ -31,18 +31,6 @@ STATIC_INIT(globals) {
 	// and assert that the global vectors are NaN before calling the raw functions here
 	// to make sure nobody (even builtins) is accidentally using them - NaN is the most likely value to expose remaining usages
 
-	// TODO make sure `isnan` actually works - potential compiler bug:
-	//LOG_INFOF("%f\n", 0.0/0.0 == 0.0/0.0);
-	//LOG_INFOF("%f\n", 0.0/0.0 != 0.0/0.0);
-	//float x = 0.0/0.0;
-	//LOG_INFOF("%f\n", x == x);
-	//LOG_INFOF("%f\n", x != x);
-
-	//float y = __builtin_nan();
-	//LOG_INFOF("%f\n", y);
-	//LOG_INFOF("%f\n", y == y);
-	//LOG_INFOF("%f\n", __builtin_isnan(y));
-
 	CLEAR_V_GLOBALS();
 }
 #endif
diff --git a/qcsrc/lib/float.qh b/qcsrc/lib/float.qh
index fa4ff77b5..b35494de4 100644
--- a/qcsrc/lib/float.qh
+++ b/qcsrc/lib/float.qh
@@ -2,4 +2,5 @@
 
 const float FLOAT_MAX = 340282346638528859811704183484516925440.0f;
 const float FLOAT_EPSILON = 0.00000011920928955078125f;
+/// Always use `isnan` function to compare because `float x = FLOAT_NAN; x == x;` gives true
 const float FLOAT_NAN = 0.0 / 0.0;
diff --git a/qcsrc/lib/warpzone/mathlib.qc b/qcsrc/lib/warpzone/mathlib.qc
index 4a7c88610..9105269ff 100644
--- a/qcsrc/lib/warpzone/mathlib.qc
+++ b/qcsrc/lib/warpzone/mathlib.qc
@@ -24,8 +24,13 @@ bool isinf(float e)
 }
 bool isnan(float e)
 {
-	float f = e;
-	return (e != f);
+	// the sane way to detect NaN is broken because of a compiler bug
+	// (works with constants but breaks when assigned to variables)
+	// use conversion to string instead
+
+	//float f = e;
+	//return (e != f);
+	return ftos(e) == "-nan";
 }
 bool isnormal(float e)
 {
@@ -217,6 +222,7 @@ float copysign(float e, float f)
 {
 	return fabs(e) * ((f>0) ? 1 : -1);
 }
+/// Always use `isnan` function to compare because `float x = nan(); x == x;` gives true
 float nan(string tag)
 {
 	return sqrt(-1);
-- 
2.39.2