From 8d20d61b4d305b985de4837bb0ed3ddaedb208d1 Mon Sep 17 00:00:00 2001
From: Brad Linden <brad@lindenlab.com>
Date: Wed, 31 May 2023 10:33:03 -0700
Subject: Fix divide by zero causing NaN with certain day cycles in DRTVWR-559

---
 indra/llinventory/llsettingsbase.cpp | 1 +
 indra/llinventory/llsettingsbase.h   | 1 +
 indra/newview/llenvironment.cpp      | 3 +++
 3 files changed, 5 insertions(+)

(limited to 'indra')

diff --git a/indra/llinventory/llsettingsbase.cpp b/indra/llinventory/llsettingsbase.cpp
index 936b166409..bcf8bf6264 100644
--- a/indra/llinventory/llsettingsbase.cpp
+++ b/indra/llinventory/llsettingsbase.cpp
@@ -693,6 +693,7 @@ void LLSettingsBlender::update(const LLSettingsBase::BlendFactor& blendf)
 F64 LLSettingsBlender::setBlendFactor(const LLSettingsBase::BlendFactor& blendf_in)
 {
     LLSettingsBase::TrackPosition blendf = blendf_in;
+    llassert(!isnan(blendf));
     if (blendf >= 1.0)
     {
         triggerComplete();
diff --git a/indra/llinventory/llsettingsbase.h b/indra/llinventory/llsettingsbase.h
index 1f0589f571..50276b801a 100644
--- a/indra/llinventory/llsettingsbase.h
+++ b/indra/llinventory/llsettingsbase.h
@@ -467,6 +467,7 @@ protected:
 
 class LLSettingsBlenderTimeDelta : public LLSettingsBlender
 {
+protected:
     LOG_CLASS(LLSettingsBlenderTimeDelta);
 public:
     static const LLSettingsBase::BlendFactor MIN_BLEND_DELTA;
diff --git a/indra/newview/llenvironment.cpp b/indra/newview/llenvironment.cpp
index aec7ceaa3c..58da164b5a 100644
--- a/indra/newview/llenvironment.cpp
+++ b/indra/newview/llenvironment.cpp
@@ -168,6 +168,9 @@ namespace
     // Find normalized track position of given time along full length of cycle
     inline LLSettingsBase::TrackPosition convert_time_to_position(const LLSettingsBase::Seconds& time, const LLSettingsBase::Seconds& len)
     {
+        // early out to avoid divide by zero.  if len is zero then jump to end position
+        if (len == 0.f) return 1.f;
+
         LLSettingsBase::TrackPosition position = LLSettingsBase::TrackPosition(fmod((F64)time, (F64)len) / (F64)len);
         return llclamp(position, 0.0f, 1.0f);
     }
-- 
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