Using CompilerInstance

Hi,

I am a clang novice and trying to navigate my way through it.

I want to read in C++ source files (multiple) and identify calls to a specific function so that I can insert a definition for it in the code. I have written my ASTconsumer for the purpose.

As suggested in various posts, I am using CompilerInstance to hold the C++ source files (one at a time) and parse the source code. At the moment I am using ParseAST on individual components of the CompilerInstance. But I suspect there must be a more elegant way to parse the source file once the CompilerInstance has been "populated". Is there a way to do so? (I have written my own driver as opposed to using command line clang.)

Also, how would one inject source code and generate the object code?
Any and all pointers would be highly appreciated.

Thanks,
Gagan