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

[Aaron Ballman]

On Wed, Nov 6, 2013 at 12:59 PM, Manuel Klimek <klimek at google.com> wrote:
> 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.

Option #2 was accepting a file path input, but returning a vector of
information -- was the file path the path to the database itself, or
to a specific source file?

~Aaron