[cfe-dev] Question about TreeTransform

[Andrew Gozillon via cfe-dev]

Thank you very much for the quick and helpful reply Richard. That pointed me in the right direction and I've managed to fix the issue I was having!


________________________________
From: metafoo at gmail.com <metafoo at gmail.com> on behalf of Richard Smith <richard at metafoo.co.uk>
Sent: 21 February 2017 21:45:07
To: Andrew Gozillon
Cc: cfe-dev at lists.llvm.org
Subject: Re: [cfe-dev] Question about TreeTransform

On 21 February 2017 at 13:36, Andrew Gozillon via cfe-dev <cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>> wrote:

Hi guys,


This might be a silly and naive question, but I was wondering if its at all possible for a type to change during a TreeTransform (I believe in general that's what the TreeTransform code is for but I could be incorrect)?

Yes, that's permitted. If you want to do so, you generally need to override the relevant Transform*Type function, and be sure to populate the TypeLocBuilder with location information for the new type. (Overriding Rebuild*Type to produce a different type will in general not work, since the type location information will be populated for the wrong type, leading to the assertion you describe below.)

For example at the moment I have a Type that acts as a wrapper for another Type (alongside some extra information), however during transformation for the wrapper Type I would like to "transform" it to the contained Type. The contained type would be something like a pointer to another type and the wrapper in essence is a throw away class.


I've given it a try but when I swap out for the contained type I get a type size error "incorrect data size provided to CreateTypeSourceInfo!" within the TypeLocBuilder.h as the type sizes don't quite match up. Basically at this stage the TypeSourceInfo is that of the Wrapper with the contained type and the QualType itself is the contained type.


So in essence my questions are, is what I'm trying to do possible? If it is, am I perhaps missing a step within my own Transform function that's required to modify the type source information appropriately?

It sounds like you are not populating the type source information for your wrapper type properly within the TypeLocBuilder.

As perhaps useful information the TypeLoc class I've based the wrapper class off of is the TypeSpecTypeLoc class.


I'd be happy to provide more information or explain a little better for the sake of clarity, if that's required. As I'm unsure if this is enough information to go off of!

If the above hints aren't enough to unstick you, a (preferably reduced) snippet of your code would help.

Thank you for your time.


Best Regards,

Andrew




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Please consider the environment and think before you print.

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