Prevent endless loop if output is not compressible. May be fixed in 4.56 beta 
diff -urw source/save/lzma443/C/7zip/Common/OutBuffer.cpp source/lzma443/C/7zip/Common/OutBuffer.cpp
--- C/7zip/Common/OutBuffer.cpp	2007-11-07 19:41:11.000000000 +0100
+++ C/7zip/Common/OutBuffer.cpp	2006-03-08 14:13:12.000000000 +0100
@@ -74,6 +74,8 @@
     UInt32 processedSize = 0;
     result = _stream->Write(_buffer + _streamPos, size, &processedSize);
     size = processedSize;
+    if (!size)
+      result = -1;
   }
   _streamPos += size;
   if (_streamPos == _bufferSize)
diff