On the detection of unstructuredness in flowgraphs (Q1098619)

We formally define the concepts of skeletons, modules, branches, entries and iteration exits in program flowgraphs. We show that two simple conditions are sufficient for the detection of unstructuredness in programs. Namely, a module \(M_ n\) will be unstructured if: (a) the node n is in one of its branches \(B_{\alpha}(n)\) but not in the corresponding skeleton \(q_{\alpha}(n)\), or (b) there are two nodes \(m_ 1\) and \(m_ 2\) in \(M_ n\) such that \(m_ 1\in q_{\beta_ 1}(p_ 1)\), \(m_ 2\in q_{\beta_ 2}(p_ 2)\) and \(m_ 2\not\in q_{\beta_ 1}(p_ 1)\) for some nodes \(p_ 1\) and \(p_ 2\) outside \(M_ n\).