GCC front-ends

LLVM is the target, right, the low-level virtual machine? Clang is the compiler toolkit. My experience with clang over a decade ago is why we opted for GCC over clang for COBOL. If the GCC API is criticized as hard to use, it has one singular advantage over clang: it exists.

Those years ago, I wanted to use clang to parse C++, and write the metadata to a database. I left with the sense that it might be possible, but I'd have to write the manual first.

(I still *do* want to write that tool. It would underpin a source-code navigation tool for C++, something that doesn't exist for large code bases. We have C-based tools like GNU Global and cscope, and I remember using a web-based text-search engine, but nothing that could distinguish open(2) from std::stream::open(), or report the call stack that modifies a variable.)

The GCC Internals manual runs some 800 pages. Even at that, the 10% of that document devoted to front-end development woefully inadequate; after all, the ISO COBOL specification is 1280 pages, and it describes only one language. But that document, plus a tutorial example, gave us a toehold. Within a week we had the "hello world" version of a COBOL compiler. Then it was just a quick 8 or so man-years of work.