duplicate a variable!!!!

[Ian Lance Taylor]

Greicy.Costa-Marques@imag.fr writes:

>> One important question
>> is going to be how you know which variable you want to duplicate.
>
> yes, i know which variables i want to duplicate.
>
>> Presumably you don't want to duplicate all variables.
>
> no, i want to duplicate all variables in my code.
>
>> Another important question is what you want to do with the
>> duplicated variable.
>
> Because I want to harden  my code.  I'm working with fault injection
> by software and I want to harden my code, and a way of hardening is
> the duplication of variables. And as I still do not know how, I chose
> to start trying for a single variable and after to use the same path
> for all variables in my code.

It's a lot easier to duplicate all variables than it is to duplicate a
single variable.

I do not know what duplicating variables has to do with hardening code.


>> If you duplicate the variable in a straightforward way, the duplicate will
>> simply be removed by the optimization passes.
>
> I want the duplication remains after optimization.

How do you propose to make that happen?  How will the program use the
duplicated variable?


> In my work I have to do that with gcc (in another words i have to
> modify the compiler so it makes it)
>
> you said is necessary to have to learn a fair amount of gcc
> infrastructure in order to do it.  Like what?

That question is too general for me to answer.  I recommend that you
read the gcc internals manual and look at the gcc source code and try to
ask more specific questions.

Ian