[llvm-dev] Dependency Info from AST

Chris Bieneman via llvm-dev llvm-dev at lists.llvm.org
Tue Sep 19 10:31:10 PDT 2017


> On Sep 19, 2017, at 10:09 AM, Siddharth Shankar Swain <h2015096 at pilani.bits-pilani.ac.in> wrote:
> 
> Hi Chris,
> Thanks for the suggestion i was trying to use the patch https://reviews.llvm.org/D30691 <https://reviews.llvm.org/D30691> and ASTimporter concept for cross file analysis. Can u explain in details the approach u suggested ?

There is a tutorial on ASTVisitors here:
http://clang.llvm.org/docs/RAVFrontendAction.html

> What is `nm` on the object files ?

nm is a standard unix tool:
https://en.wikipedia.org/wiki/Nm_%28Unix%29 <https://en.wikipedia.org/wiki/Nm_(Unix)>

-Chris

> Can u suggest some approach to start on this cross file analysis tool. 
> Thanks,
> Siddharth
> 
> On Tue, Sep 19, 2017 at 9:42 PM, Chris Bieneman <beanz at apple.com <mailto:beanz at apple.com>> wrote:
> (Apologies for the re-send Siddharth, I failed to cc the list)
> 
> There is no existing tool that I'm aware of which performs this analysis on the AST. It is possible to do on an AST. You would just need to write an AST Visitor that finds declarations, definitions, and uses of functions.
> 
> Is there a reason you need to do this at the AST level? With C code this analysis can be trivially performed with `nm` on the object files, so if you don't have a strong reason for needing to do this on the AST I'd just write a script to wrap `nm` rather than writing an AST Visitor.
> 
> -Chris
> 
> > On Sep 14, 2017, at 6:57 AM, Siddharth Shankar Swain via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
> >
> > Hi,
> > Can anyone help if for example we have multiple c files and we want to analyze their ASTs to find out any dependency between them ( like a function defined in one c file is used in other, any external variable etc ). How can we do it at the AST level? I mean is there any automated tool or flag for it in LLVM. If anyone has any idea please tell.
> > sincerely,
> > Siddharth
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