From 6a77eb1dcfdfa9ba7a66b64e4ead590c503e536c Mon Sep 17 00:00:00 2001
From: Thompson Lee <tom.mai78101@gmail.com>
Date: Fri, 5 Aug 2016 01:02:54 -0400
Subject: [PATCH] Added @mtheall 's Mtx_Multiply() enhancement.

---
 source/maths/mtx_multiply.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/source/maths/mtx_multiply.c b/source/maths/mtx_multiply.c
index 5182efa..f7d5b54 100644
--- a/source/maths/mtx_multiply.c
+++ b/source/maths/mtx_multiply.c
@@ -1,7 +1,16 @@
 #include <c3d/maths.h>
 
-void Mtx_Multiply(C3D_Mtx* __restrict out, const C3D_Mtx* a, const C3D_Mtx* b)
+void Mtx_Multiply(C3D_Mtx* out, const C3D_Mtx* a, const C3D_Mtx* b)
 {
+	// if out is a or b, then we need to avoid overwriting them
+	if(out == a || out == b)
+	{
+		C3D_Mtx tmp;
+		Mtx_Multiply(&tmp, a, b);
+		Mtx_Copy(out, &tmp);
+		return;
+	}
+
 	// http://www.wolframalpha.com/input/?i={{a,b,c,d},{e,f,g,h},{i,j,k,l},{m,n,o,p}}{{α,β,γ,δ},{ε,θ,ι,κ},{λ,μ,ν,ξ},{ο,π,ρ,σ}}
 	int i, j;
 	for (j = 0; j < 4; ++j)