From 0e9eabdb189f520441cb0a0161df9ca3881f89b1 Mon Sep 17 00:00:00 2001
From: Andrew Noyes <andrew.noyes@snowflake.com>
Date: Wed, 23 Jun 2021 09:24:52 -0700
Subject: [PATCH] Cherry-pick UBSAN fix

from https://github.com/Tencent/rapidjson/commit/16872af88915176f49e389defb167f899e2c230a
---
 fdbclient/rapidjson/internal/stack.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fdbclient/rapidjson/internal/stack.h b/fdbclient/rapidjson/internal/stack.h
index 7ab15d42a0..fa43aa0171 100644
--- a/fdbclient/rapidjson/internal/stack.h
+++ b/fdbclient/rapidjson/internal/stack.h
@@ -17,6 +17,7 @@
 
 #include "../allocators.h"
 #include "swap.h"
+#include <cstddef>
 
 #if defined(__clang__)
 RAPIDJSON_DIAG_PUSH
@@ -106,7 +107,7 @@ public:
 	template <typename T>
 	RAPIDJSON_FORCEINLINE void Reserve(size_t count = 1) {
 		// Expand the stack if needed
-		if (RAPIDJSON_UNLIKELY(stackTop_ + sizeof(T) * count > stackEnd_))
+		if (RAPIDJSON_UNLIKELY(static_cast<std::ptrdiff_t>(sizeof(T) * count) > (stackEnd_ - stackTop_)))
 			Expand<T>(count);
 	}
 
@@ -118,7 +119,7 @@ public:
 
 	template <typename T>
 	RAPIDJSON_FORCEINLINE T* PushUnsafe(size_t count = 1) {
-		RAPIDJSON_ASSERT(stackTop_ + sizeof(T) * count <= stackEnd_);
+		RAPIDJSON_ASSERT(static_cast<std::ptrdiff_t>(sizeof(T) * count) <= (stackEnd_ - stackTop_));
 		T* ret = reinterpret_cast<T*>(stackTop_);
 		stackTop_ += sizeof(T) * count;
 		return ret;