infer_clone/infer/src/clang/README.md

Clang Front-End

This is the front-end for the clang compiler.

The main entry point is ClangWrapper.

General structure

1. Given a compilation command from the build system, sanitize it, attach ASTExporter clang plugin to the relevant commands and run it.
2. Parse the AST from Biniou format to OCaml data structure.
3. (optional) Invoke translation to SIL via CFrontend.
4. (optional) Invoke linters via CFrontend_checkers_main. More on linters

Format of the AST

OCaml data structure is defined in atd format. The clang_ast_t.atd file is generated from comments in ASTExporter.h file.

For more information, refer to the relevant documentation in facebook-clang-plugins:

• libtooling/ATD_GUIDELINES.md
• clang-ocaml/README.md

Hacking on .atd file

1. Create a simple example (example.cpp) source file with construct that needs to be exported. The smaller the better.
2. Export extra information by changing code in libtooling/ASTExporter.h. For more information, refer to the ATD_GUIDELINES.
3. Compile Infer with the new version of facebook-clang-plugins. Running make all from top level of Infer repository will do that. Sometimes there may be compilation errors due to .atd file changes - they need to be fixed.
4. Use newly exported information information in the frontend.

Tips & Tricks:

• To view the AST in a human readable version, Infer can generate .bdump file: infer -g -- clang -c example.cpp && sh example.cpp.ast.sh. Then open example.cpp.ast.bdump
• To inspect ast dump visually: clang -c example.cpp -Xclang -ast-dump. It doesn't include all the information that Infer sees, but it's pretty concise
• If running bdump is failing (it happens on huge sources sometimes), there is a way to view it in "Yojson" format. To do that, replace all occurrences of BiniouASTExporter with YojsonASTExporter in .ast.sh script.