I think a bit of pseudo code might be good to demonstrate roughly what I had in
mind:
```
template <typename ConcreteType, template <typename T> class...
Traits>
class WithTrait : public Traits<ConcreteType>... {
protected:
WithTrait(){};
friend ConcreteType;
};
template <typename ConcreteType, template <typename> class
TraitType>
class TraitBase {
protected:
ConcreteType &Object() { return static_cast<ConcreteType
&>(*this); };
};
template <typename ConcreteType>
class SourceMgr : public TraitBase<ConcreteType, SourceMgr> {
public:
.... source mgr interface functions ....
};
class DefaultSourceMgr : public WithTrait<DefaultSourceMgr, SourceMgr> {
..... implementation ....
}
```
This way function that want to use SourceMgr would need a template but that
template can be defaulted to `DefaultSourceMgr`. I hope I could demonstrate my
thoughts clear enough.
As for the functionality I need in the sourcemgr, my compiler uses namespaces as
the center piece and the unit of compilation, i want my source manager to accept
a namespace name and load the source code of that namespace. At the moment I had
to copy paste the llvm::SourceMgr and manually tweak it.
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Tuesday, September 7th, 2021 at 1:03 AM, David Blaikie <dblaikie at
gmail.com> wrote:
> 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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