A code smell is any part of an application code that might indicate a code or design problem, which makes the application code hard to evolve and maintain. Automatic detection of code smells has been studied to help programmers find which parts of their application codes should be refactored. However, code smells have not been defined in a formal manner. Moreover, existing detection tools are designed for object-oriented applications, but rarely provided for high performance computing (HPC) applications. HPC applications are usually optimized for a particular platform to achieve a high performance, and hence have special code smells called platform-specific code smells (PSCSs). The purpose of this work is to develop a code smell alert system to help programmers find PSCSs of HPC applications to improve the performance portability across different platforms. This paper presents a PSCS alert system that is based on an abstract syntax tree (AST) and XML. Code patterns of PSCSs are defined in a formal way using the AST information represented in XML. XML Path Language (XPath) is used to describe those patterns. The evaluation results obtained by using real applications show that the proposed system can alert potential PSCSs to programmers.