  Symbolic execution has shown its ability to find security-relevant flaws in
software, but faces significant scalability challenges. There is a commonly
held belief that manual intervention by an expert can help alleviate these
limiting factors. However, there has been little formal investigation of this
idea. In this paper, we present our experiences applying the KLEE symbolic
execution engine to a new bug corpus, and of using manual intervention to
alleviate the issues encountered. Our contributions are (1) Hemiptera, a novel
corpus of over 130 bugs in real world software, (2) a comprehensive evaluation
of the KLEE symbolic execution engine on Hemiptera with a categorisation of
frequently occurring software patterns that are problematic for symbolic
execution, and (3) an evaluation of manual mitigations aimed at addressing the
underlying issues of symbolic execution. Our experience shows that manual
intervention can increase both code coverage and bug detection in many
situations. It is not a silver bullet however, and we discuss its limitations
and the challenges encountered.

Software Engineering