cpp

Example grammar for C++

This example shows how to parse C++ files with DParserGen. It contains two grammars and an additional file with shared rules:

• grammarcpreproc.ebnf splits the input in tokens and represents preprocessor constructs.
• grammarcpp.ebnf defines the structure of a C++ file, which is already preprocessed.
• grammarcppcommon.ebnf contains rules, which are used by both grammarcpreproc.ebnf and grammarcpp.ebnf.

The grammar is for C++11, but also contains some newer constructs and extensions supported by GCC or MSVC. It is possible to extract the grammar from the LaTeX source of different versions of the stardard draft in https://github.com/cplusplus/draft using the D program grammarcppgen.d, but the extracted grammar also needs some manual modifications.

File testcpp.d contains an example for using the C++ grammars. First it will parse the structure for the preprocessor using grammarcpreproc.ebnf. Using option -p it will print this tree and directly exit. Otherwise it will pass the tokens to a parser for grammarcpp.ebnf and print the resulting tree. The C++ file needs to be already preprocessed, because most preprocessor directives are not handled by the example. The grammar for C++ contains some ambiguities, so the parser uses GLR. Subtrees for ambiguities will have names starting with "Merged:". The printed trees will by default not show null subtrees and flatten arrays. The full tree can be printed with option -v.

The application can be built with the following command:

dub build

The following command starts the application with file test.cpp as input:

./example_cpp test.cpp