[cfe-dev] Getting source files into the CompilationDatabase interfaces

[Manuel Klimek]

On Wed, Nov 6, 2013 at 9:50 AM, Aaron Ballman <aaron at aaronballman.com>wrote:

> On Wed, Nov 6, 2013 at 12:34 PM, Manuel Klimek <klimek at google.com> wrote:
> > Hi,
> >
> > as we've seen more use of the compilation database (for example through
> the
> > YCM vim plugin), we noticed that for networked build systems and server
> > applications the information we currently expose in the interfaces (path,
> > file-name, command line arguments) is not enough - we also need to be
> able
> > to get all source code, which we then can put into clang's VFS to get a
> > fully build-system independent clang run over a translation unit.
> >
> > We think that getting the source information (perhaps optionally) as
> part of
> > a getCompileCommands run is a good fit - a build system always must know
> how
> > to provide the required sources, and as such it seems to be a natural
> fit.
>
> I think the premise is sound; it's information that's useful, and
> something the compilation database can definitely provide.
>
> > I'd propose to change the CompilationDatabase interface
> > (tools/clang/include/clang/Tooling/CompilationDatabase.h) to that end,
> and
> > see two possible solutions, which both have different pros and cons:
> > 1. Add a map from std::string (file-name) -> std::string (source
> content) to
> > the CompileCommand class (in
> > tools/clang/include/clang/Tooling/CompilationDatabase.h); let specific
> > CompilationDatabases optionally fill in that information
> > 2. Do not modify CompileCommand - instead, add a
> > getCompileCommandsAndSources(StringRef FilePath) method that returns a
> > vector<pair<CompileCommand, map<string, string>>> which also includes the
> > sources; I'm reluctant to split the call into two, as the compile command
> > and the sources are tightly coupled (if a user syncs in the background,
> both
> > tend to change at the same time)
>
> Can we have a bit more information about these two options?  I think I
> may be a bit confused.  Option #1 sounds like it maps a file name to
> the file contents.  But I can't seem to make heads or tails of what
> the input and outputs are for Option #2.
>

Ah, both basically would additionally provide a map<string, string> that
maps from filenames to file contents, so a client can overlay those file
contents to get a fully hermetic "replay" of the compilation.

The difference is that option #1 would basically keep the old interface,
and optionally the compilation database could provide the file contents (if
it wants), while option #2 would introduce a new interface for clients to
ask for file contents explicitly if they need it.


>
> Thanks!
>
> ~Aaron
>
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