[cfe-dev] clang driver -- pre-preprocessing job/function

[David McNamara]

I've spent the last couple of hours looking at the clang-driver and am 
about to try and make some changes -- I have a fair amount of confidence 
that I can get done what I need to get done but I want to make sure I 
really use the clang-driver framework rather than just a hack to get the 
job done.

What I need to do is the following:

If a certain command line argument is present, then do a special 
pre-preprocessing job (actually, replacing the preprocessor with my own 
preprocessor)

I believe I should add this argument in 
~tools/clang/include/clang/Driver/Options.td -- perhaps adding a special 
"OptionGroup" type or just using the CompileOnly_Group (a special option 
group might help identify that the special arg is present and to be able 
to delete it later after my special preprocessing job)

When this argument is present -- I need to pass the preprocessing 
arguments (-D, -I,.. ) and my special arguments to a new job (could 
actually be a linked in call) -- when that job is finished, I 
essentially want to continue the compilation process as it was requested 
(compilation only, linking, etc...) only eliminating my special-args.  
This special preprocessing would only occur when some compilation is to 
be done (source files are present) and the result would be replacing the 
source-files with the modified preprocessor name.

I'm thinking these steps should either be added in BuildCompilation of 
BuildJobs (~tools/clang/lib/Driver/Driver.cpp).

At least one other alternative would be to do the special preprocessing 
right when the actual "normal" preprocessing is done...  either by a 
library call or with ExecuteCommand (not sure which is preferable).  
Might be the cleanest way since I essentially just have to replace the 
normal-preprocessor with my preprocessor (haven't found the function for 
that yet).

It looks like another way to do it would be through "requested plugins" (?)

Not sure which implementation path to take -- any suggestions?

Regards,
  David