Fix undefined behavior sanitizer violations

- memcpy can't be called with nullptr
- chunk headers should be aligned to 8 bytes as they contain uint64_t

src/build.cpp

@@ -298,7 +298,8 @@ static ChunkData prepareChunkData(const Chunk& chunk)
 		const File& f = chunk.files[i];
 
 		memcpy(result.data.get() + nameOffset, f.name.c_str(), f.name.length());
-		memcpy(result.data.get() + dataOffset, f.contents.data(), f.contents.size());
+		if (f.contents.size())
+			memcpy(result.data.get() + dataOffset, f.contents.data(), f.contents.size());
 
 		DataChunkFileHeader& h = reinterpret_cast<DataChunkFileHeader*>(result.data.get())[i];
 

src/update.cpp

@@ -186,15 +186,18 @@ static bool processFile(Output* output, BuildContext* builder, UpdateFileIterato
 	{
 		std::unique_ptr<char[]> extra(new (std::nothrow) char[chunk.extraSize]);
 		std::unique_ptr<char[]> index(new (std::nothrow) char[chunk.indexSize]);
-		std::unique_ptr<char[]> data(new (std::nothrow) char[chunk.compressedSize + chunk.uncompressedSize]);
+
+		size_t uncompressedOffset = (chunk.compressedSize + 7) & ~7; // make sure uncompressed data is aligned
+
+		std::unique_ptr<char[]> data(new (std::nothrow) char[uncompressedOffset + chunk.uncompressedSize]);
 
 		if (!extra || !index || !data || !read(in, extra.get(), chunk.extraSize) || !read(in, index.get(), chunk.indexSize) || !read(in, data.get(), chunk.compressedSize))
 		{
 			output->error("Error reading data file %s: malformed chunk\n", path);
 			return false;
 		}
 
-		char* uncompressed = data.get() + chunk.compressedSize;
+		char* uncompressed = data.get() + uncompressedOffset;
 
 		processChunkData(output, builder, fileit, stats, chunk, uncompressed, data, index, extra);
 	}