From 92bec5a5a629ac0e82d3ac91a46ff19b78816b52 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sun, 15 Mar 2026 02:00:03 +0000
Subject: Avoid UB in calculating member offset

Bit hacky; local dummy var to base a fake pointer on.
---
 gfx/gl/glVertexArray.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/gfx/gl/glVertexArray.h b/gfx/gl/glVertexArray.h
index 791f74f..323303c 100644
--- a/gfx/gl/glVertexArray.h
+++ b/gfx/gl/glVertexArray.h
@@ -11,10 +11,12 @@ namespace Impl {
 		template<typename M, typename T> struct MP {
 			constexpr MP(M T::* ptr) : ptr {ptr} { }
 
+			constexpr
 			operator GLuint() const
 			{
-				return static_cast<GLuint>(reinterpret_cast<const char *>(&(static_cast<T *>(nullptr)->*ptr))
-						- static_cast<const char *>(nullptr));
+				constexpr static char dummy {};
+				return static_cast<GLuint>(reinterpret_cast<const char *>(&(reinterpret_cast<const T *>(&dummy)->*ptr))
+						- reinterpret_cast<const char *>(&dummy));
 			}
 
 			M T::* ptr;
-- 
cgit v1.3