[cfe-commits] Design proposal: Add custom compilation database formats as plugins

[Chandler Carruth]

On Wed, Jul 18, 2012 at 3:11 PM, Sean Silva <silvas at purdue.edu> wrote:

> > For ninja in particular, I have long thought that the correct approach
> is to write something which can convert 'ninja -t commands' into the JSON
> format, or to build a tool for writing the JSON database directly into
> ninja.
>
> This was my line of thought as well.
>
> Since the C++ stdlib unfortunately doesn't have JSON support, what do
> you think about a simpler, more plaintext-y compilation database
> (PlaintextCompilationDatabase?); it seems like that might be a win
> since it is simpler to output. For example, the format would just be
>
> /path/to/dir/
> clang++ foo.cpp
> foo.cpp
> <empty line>
>
> Just a mirror of the JSON one, but with a format easier to output (god
> forbid there's a newline in one of the command lines or filenames). On
> the other hand, throwing together a simple "good-enough" JSON writer
> isn't *too* difficult; nonetheless, for tools written in C/C++, this
> could lower the bar to entry. Do you know what CMake currently does?
> Does it have its own mini JSON writer?
>

We didn't go with the plaintext route for three important reasons:

1) Filenames do have whitespace in them. The format should be robust
against that.
2) Many other tools and languages should have a minimal barrier to read
them. An existing format eases this.
3) It is *incredibly* easy to write a minimal JSON writer that only
supports the features we need.

Manuel contributed the CMake support for the JSON database, and it includes
just such a trivial JSON writer. =] We can easily place a copy of the code
into LLVM or re-license it however it helps.

That said, the latest version of CMake already has support for JSON + Ninja
-- we didn't contribute it, so I don't know what strategy they followed,
but you should look at that and talk to the ninja and CMake developers
before going too far here.
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