[llvm-dev] Extending the SouceMgr

[David Blaikie via llvm-dev]

On Mon, Sep 6, 2021 at 4:58 PM lxsameer <lxsameer at lxsameer.com> wrote:

> Sorry about the terminology, I was thinking about CRTP style traits. I see
> CRTP based classes and templates quite often it the LLVM source code.
>

Yeah, there's a fair bit of CRTP, and traits, but they are different things
- https://www.internalpointers.com/post/quick-primer-type-traits-modern-cpp
discusses traits, for some details.


> So I think the current SourceMgr can be renamed to something like
> `DefaultSourceManager` that implement the `SourceMgr` CRTP trait ( sorry I
> don't know the exact term here).
>

I'm still a bit unclear on how the existing SourceMgr-using code would work
- it'd have to be updated to be templated on the specific SourceMgr
implementation in use, would it? Some other ideas?

Might be worth a more narrowly defined discussion about what
extensibility/features you're looking for in SourceMgr, without the need to
create a whole new hierarchy.


>
>
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Tuesday, September 7th, 2021 at 12:50 AM, David Blaikie <
> dblaikie at gmail.com> wrote:
>
> On Mon, Sep 6, 2021 at 3:59 PM lxsameer via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hey folks,
>> Hope you're doing well.
>>
>>
>> It seems to me that it is not possible to extend the current behavior  of
>> `llvm::SourceMgr` (at least I couldn't think of any solution) and it is
>> quite C/C++ish ( for lack of a better word).
>>
>> For my use case, I need to tweak it a little bit and since there is now
>> way to do that, I have to write my own which means I'm going to lose the
>> ability to use any llvm api that expect a source manager and that's a big
>> price to pay.
>>
>> It seems that the source manger will benefits from a trait like design.
>> This way, any front end that need a customized source manager can easily do
>> that and the current source manager would be an implementation of that
>> trait.
>>
>
> I /think/ the C++ terminology that's a closer match for what you're
> describing might be a "concept" rather than a "trait"?
>
> But then, if I'm understanding correctly, all the code that currently is
> written in terms of the SourceMgr would have to become a template so it can
> be used by different implementations of the SourceMgr concept? That, at
> first guess, seems unlikely/infeasible?
>
>  - Dave
>
>
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