Parsing statement list program using flex and bison

Static program analysis is to analyze computer software performed without actually executing programs. The main benefits lie in checking the correctness of safety critical systems and improving the efficiency of software developers. Nowadays, static program analysis has been gradually applied to PLC programs based on IEC 61131-3, but still cannot adapt to most of the proprietary languages used by vendors. To solve this problem in this paper, a general approach is proposed. The approach is verified by an example of STEP7 STL from Siemens, using flex and bison to automatically generate a parser of STL program. Additionally, we introduce issues and solutions that exist in the semantic of STL, effectively implementing the front-end of the static program analysis.