I’ve been working on a (nearly finished) Javascript project for a little over 14 months now. The project started out as a hack I expected to finish overnight, but over time the Javascript part has grown up to be 68 separate files and 10,314 non-empty lines, sadly currently dependent on the C preprocessor for building.
It’s hard to explain how I ended up using cpp for the Javascript: this was only a hack, and I needed something that gave me macro expansion, ifdef, define, and includes without too much effort. After about 3 second’s consideration, I realized cpp was “perfect” for the task:
- Provide a LOG() macro that disappears in release mode.
- Provide an ASSERT() macro that disappears in release mode, and generates exceptions tagged with original file and line number.
- Swap LOG() and ASSERT() implementations for code that allows producing a “checked” build, which logs events in a compact form as they occur, that are reported back to the server if a crash occurs.
- Replacing PROJECT_SOME_CONFIG_VAR_NAME with “1”, based on a configuration file shared with the Python backend.
Like all true hacks, this hack is now so hard-coded into the project that I truly hate to even think about the work that will be required to replace it. My project is reaching the stage where I want to move the code base to its own dedicated test server (rather than my laptop), however on setting up a Linux instance, I’ve discovered that GNU cpp versions after 4.1 no longer preprocess the Javascript with crashing out with an error.
Rather than add a specific version of GCC to the list of build requirements, I figured now would be a good time to truly fix this mess. My problem is, though, that I can’t find a replacement preprocessor with the same power and features as cpp! I have considered m4, but m4 is a world of pain unto itself. Other Javascript-specific preprocessors I have found lack all the features I am currently depending on, e.g.:
__FILE__&__LINE__- Variadic macros
- Include guards
- Token concatenation
- Conditional compilation
I am seriously considering implementing a brand new preprocessor just for Javascript, that completely borrows the C preprocessor syntax since it has worked so well. I’m just wondering if there are better options before doing so. 🙂 Perhaps there is already a cpp-like generic preprocessor I could swap in? The work required to replace all the preprocessor syntax in those 68 files approaches the amount of work required to simply reimplement the preprocessor.
I’m quite surprised I ever made it so far while relying on the C preprocessor; it is more effective at this task than healthy for the mind to comprehend. Another option open to me is statically building versions of cpp-4.1 for Linux, Darwin-i386, Win32, and storing those binaries in the project’s repository.
Help!
Have you already tried mcpp? It’s a “portable C preprocessor”
Should that fail, you could try using a generic macro processor (like gema) and build enough cpp on top of it.