[cfe-dev] Clang tooling and absolute filenames

[Jonathan Anderson]

Hi, 

I've written a Clang tool that does some analysis of a C program and uses the results to guide instrumentation of the resulting LLVM IR. This tool (and the attendant research) wouldn't have happened without Clang, so thanks to all you maintainers! I have encountered one problem, however, which is trivial to fix but seems to be deeply embedded in someone's philosophy of The Way Things Should Be Done.

My issue is that Clang and libClangTooling disagree about the name of the C file they operate on: Clang is (quite sensibly) happy to compile "foo.c", but when I run my Clang tool, it is converted to "/Users/jon/Documents/.../myproject/foo.c" (on line 242 of lib/Tooling/Tooling.cpp). Since Clang (the binary) disagrees with Clang (the library), I have to resort to a sed script that strips `pwd` out of my Clang tool's output!

I can easily modify Tooling.cpp to use the filename passed to libClangTooling, and I would've submitted a patch with this e-mail, but there are tests and document that assume compile_commands.json will always contain absolute filenames. This seems wrong to me: shouldn't the canonical name of a file be whatever was passed to the compiler at the command line? Since tools like clang-check already provide arguments that separate the working directory from filenames, why do we have to refer to absolute filenames in compile_commands.json?


Jon
-- 
Jonathan Anderson

Research Associate
Computer Laboratory
University of Cambridge

jonathan.anderson at cl.cam.ac.uk
+44 1223 763 747