[cfe-dev] Need Help Printing Preprocessed Code and Modifying CFG

[Kevin Boos]

David,

Thanks, I'll take a look at ASTMatchers.

The purposes of the analysis is to generate a subset of the source, where
this subset is effectively a slice of statements that affect a given
CallExpr (with certain extra statements added into that subset). I realize
that slicing is better achieved with LLVM; I have already done this. This
needs to be at the source level. My problem is merely how to delete a
statement or other type of node from an AST or CFG, and then re-write the
preprocessed source as output.

Thanks,
Kevin


On Wed, Jul 3, 2013 at 9:47 AM, David Blaikie <dblaikie at gmail.com> wrote:

> Attempting source to source transformations this way (via the ast/cfg) is
> generally not recommended. These devices are not intended (and thus don't
> work very well) for this purpose.
>
> What's the goal of transforming the source in this way? If you're trying
> to instrument/test the resulting program behavior, consider an approach
> like the sanitizers (address/memory/thread sanitizer) that instruments code
> within clang's generation phase. If you're attempting to rewrite code,
> consider something like the ASTMatchers & tooling library.
> On Jul 2, 2013 7:06 PM, "Kevin Boos" <kevinaboos at gmail.com> wrote:
>
>> Hello all,
>>
>> I'm working with a Clang plugin (it must be a plugin for kernel
>> compilation reasons) that analyzes drivers in the Linux kernel for
>> virtualization security purposes.
>>
>> I start by modifying the body of a function in a way that certain
>> statements are deleted. Then I need to print out that modified source code
>> so that it can be compiled and preferably human-readable. However, I want
>> to expand all macros so that there are minimal external symbols in the
>> generated code. I tried using the Rewriter class for this, but the Rewriter
>> apparently prints out original source code only and cannot expand macros...
>> *is there an alternative source printer that can print the preprocessed
>> code? *
>> For reference, when calling "printPretty()" on the function's body Stmt*,
>> the macros are expanded just like I want.
>>
>> My second question is about actually deleting those certain statement
>> nodes in a CFG. I remember reading somewhere in the Clang docs that the CFG
>> is a constant data structure that can't be modified.* Is there a way to
>> delete statements from the underlying AST so that they wouldn't appear in
>> the CFG and also not appear in the re-printed source code? * To be
>> clear, I'm using the CFG for other analysis reasons, but I don't really
>> care if the Stmt nodes are deleted from the AST directly or from inside a
>> CFG basic block.
>>
>> Thanks in advance,
>> Kevin Boos
>> Rice University Ph.D. Candidate
>>
>> _______________________________________________
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>> cfe-dev at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>>
>>
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