From 5a95c5dd14444f60eb7e36b3a941e469e5e638ff Mon Sep 17 00:00:00 2001
From: mitaclaw <140017135+mitaclaw@users.noreply.github.com>
Date: Sun, 1 Sep 2024 19:35:56 -0700
Subject: [PATCH] CachedInterpreterEmitter: Fix `std::memcpy` UB

I wasn't aware that even with a size of zero, it's still not safe to pass a nullptr to `std::memcpy`. When `CachedInterpreterEmitter::PoisonCallback` is written, UB is happening.
---
 .../Core/PowerPC/CachedInterpreter/CachedInterpreterEmitter.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Source/Core/Core/PowerPC/CachedInterpreter/CachedInterpreterEmitter.cpp b/Source/Core/Core/PowerPC/CachedInterpreter/CachedInterpreterEmitter.cpp
index 8422ef9edb..ffd1042594 100644
--- a/Source/Core/Core/PowerPC/CachedInterpreter/CachedInterpreterEmitter.cpp
+++ b/Source/Core/Core/PowerPC/CachedInterpreter/CachedInterpreterEmitter.cpp
@@ -19,6 +19,8 @@ void CachedInterpreterEmitter::Write(AnyCallback callback, const void* operands,
   }
   std::memcpy(m_code, &callback, sizeof(callback));
   m_code += sizeof(callback);
+  if (size == 0)
+    return;
   std::memcpy(m_code, operands, size);
   m_code += size;
 }