From c25e128f3a9ff395263f3d107cbb6f059cda67d2 Mon Sep 17 00:00:00 2001
From: Dan Engelbrecht <dan.engelbrecht@epicgames.com>
Date: Fri, 30 Sep 2022 15:31:52 +0200
Subject: Handle zero size file mapping (#177)

* Handle edgecase with zero size memory mapping of file
* changelog
---
 zencore/iobuffer.cpp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

(limited to 'zencore')

diff --git a/zencore/iobuffer.cpp b/zencore/iobuffer.cpp
index 37ef57c2d..177b7dfb6 100644
--- a/zencore/iobuffer.cpp
+++ b/zencore/iobuffer.cpp
@@ -267,9 +267,18 @@ IoBufferExtendedCore::Materialize() const
 	if (m_Flags.load(std::memory_order_relaxed) & kIsMaterialized)
 		return;
 
-	void*	 NewMmapHandle;
 	uint32_t NewFlags = kIsMaterialized;
 
+	if (m_DataBytes == 0)
+	{
+		m_Flags.fetch_or(NewFlags, std::memory_order_release);
+		// Fake a "valid" pointer, nobody should read this as size is zero
+		m_DataPtr = reinterpret_cast<uint8_t*>(&m_MmapHandle);
+		return;
+	}
+
+	void* NewMmapHandle;
+
 	const uint64_t MapOffset				= m_FileOffset & ~0xffffull;
 	const uint64_t MappedOffsetDisplacement = m_FileOffset - MapOffset;
 	const uint64_t MapSize					= m_DataBytes + MappedOffsetDisplacement;
-- 
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