[Bf-blender-cvs] [4cbcfd22f5d] master: Fix T94442: Trim curve node can crash with duplicate point

[Hans Goudey]

Commit: 4cbcfd22f5d26e3cb520fa0ee0d85eedf018bab9
Author: Hans Goudey
Date:   Tue Dec 28 12:22:14 2021 -0600
Branches: master
https://developer.blender.org/rB4cbcfd22f5d26e3cb520fa0ee0d85eedf018bab9

Fix T94442: Trim curve node can crash with duplicate point

The calculation to find the factor between two evaluated points assumed
that the points were not at the same location. This assumption is some-
what reasonable, since we might expect `lower_bound` to skip those
point anyway. However, the report found a case where the first two
evaluated points were coincident, and there is no strong reason not
to make this safe, so add a check for 0 length before the division.

===================================================================

M	source/blender/blenkernel/intern/spline_base.cc

===================================================================

diff --git a/source/blender/blenkernel/intern/spline_base.cc b/source/blender/blenkernel/intern/spline_base.cc
index 4ff392a5ddb..857022345f3 100644
--- a/source/blender/blenkernel/intern/spline_base.cc
+++ b/source/blender/blenkernel/intern/spline_base.cc
@@ -417,7 +417,9 @@ Spline::LookupResult Spline::lookup_evaluated_length(const float length) const
   const int next_index = (index == this->evaluated_points_size() - 1) ? 0 : index + 1;
 
   const float previous_length = (index == 0) ? 0.0f : lengths[index - 1];
-  const float factor = (length - previous_length) / (lengths[index] - previous_length);
+  const float length_in_segment = length - previous_length;
+  const float segment_length = lengths[index] - previous_length;
+  const float factor = segment_length == 0.0f ? 0.0f : length_in_segment / segment_length;
 
   return LookupResult{index, next_index, factor};
 }