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Re: Gcc plugin for modification of source code ?

On Sun, 2014-06-15 at 02:40 +0530, Mohsin Khan wrote:
> Hi,
> I'm working on a gcc plugin project. I had a doubt, can somebody help
> me on this.

[no need to ask on gcc-help@; plugins are definitely gcc internals
related and should better be discussed on]

> Can we write a plugin (which works after a pass like cfg or any other)
> which can modify the source code of .C file, for example insert
> comments before function definitions or insert a new IF Block in the
> .C file. And after modification it writes the entire modified code to
> a new .C file. Is this type of plugin possible in GCC. If yes, please
> tell me how and if No, please tell me why.

If your source file does not contain any #line directive, a GCC plugin
(or a MELT extension, see for more) is able to get
the source code position of every Gimple instruction. (But did you think
about instruction obtained by some macro expansions?).

With that information, you can indeed transform the C source as you
wish. It might not be simple (you need to build an editor-like internal
represention of each line of the source code).

However, modifying the Gimple representation (without modifying any C++
source file) is probably simpler.

What exactly do you want to achieve? Are you sure that a source to
source transformation is worthwhile -given that you can transform
internal GCC representations like Gimples-?


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