From dc50fbbb9bc3d22cbf27f5bc4f1817c8166c5f41 Mon Sep 17 00:00:00 2001
From: Kyle Bayes <kylebayes@google.com>
Date: Wed, 19 Mar 2025 04:20:06 -0700
Subject: [PATCH] Add safeguard if n is invalid in GJK.

PiperOrigin-RevId: 738340065
Change-Id: I2288eb731621e5b84dcc0f078d8dbd84dca94cd4
---
 src/engine/engine_collision_gjk.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/engine/engine_collision_gjk.c b/src/engine/engine_collision_gjk.c
index d54f1d5e..80761c7a 100644
--- a/src/engine/engine_collision_gjk.c
+++ b/src/engine/engine_collision_gjk.c
@@ -240,6 +240,15 @@ static void gjk(mjCCDStatus* status, mjCCDObj* obj1, mjCCDObj* obj2) {
       lambda[n++] = lambda[i];
     }
 
+    // SHOULD NOT OCCUR
+    if (n < 1) {
+      status->gjk_iterations = k;
+      status->nsimplex = 0;
+      status->nx = 0;
+      status->dist = mjMAXVAL;
+      return;
+    }
+
     // get the next iteration of x_k
     mjtNum x_next[3];
     lincomb(x_next, lambda, n, simplex[0].vert, simplex[1].vert,