This repository contains a demonstration of the limitations of parsing C kernel source files using a deterministic grammar. While it is possible to parse C and C++ languages separately with a deterministic grammar, the combination of C and C preprocessor (cpp) can make parsing together very difficult.

The main reason for this is not the complexity of the languages, but the use of the C preprocessor, especially ifdefs and macros. When C and cpp are combined, they create a union of two languages that are easy to parse separately but very hard to parse together.

The resulting grammar could be very large, contain many ambiguities, and be very different from the original C grammar.

While tools like Coccinelle semantic patch use a lot of heuristics to overcome these problems, the effort of implementing the same compared with the benefits discourages this practice.

This repository serves as a proof of concept for the limitations of parsing C kernel source files with a deterministic grammar. It demonstrates the challenges that arise when attempting to parse a language that includes both C and cpp, and highlights the need for alternative approaches to parsing C kernel source files.

The demonstrator is able to parse not simple preprocessed c files but it is unable to cope with complex macros.