DMD as a library - recap, next steps

[Stefan Koch]

On Tuesday, 16 June 2020 at 04:13:10 UTC, RazvanN wrote:

> - Further strip the AST nodes of functions that require 
> semantic analysis so that we can remove the code duplication in 
> ASTBase
The AST without SemA is useless.


> - Refactor dmd to offer a decent interface. Sometimes people 
> argue against this point by saying that some changes affect the 
> compilation time of the compiler. Honestly, it takes 5 seconds 
> to compile dmd, even if we double that time I say it is worth 
> it if we gain a decent interface for dmd-as-a-lib.

No if we double that time, it's a massive change to the rapid
development we can have right now.
Try compiling DMD with LDC and you'll see what I mean

> In the mean time there were some PRs that regressed the state 
> of dmd as a lib, PRs such as this one: 
> https://github.com/dlang/dmd/pull/9010 . That PR makes it 
> impossible for someone to override the type semantic.

Why would you ever need or want to OVERRIDE semantic.
If you override semantics than by definition you are no longer,
in the same language space.

> Me and Edi are in the position where we can use bachelor 
> students to do the heavy-lifting on helping this project to 
> cross the finish line, however, it is critical that the Dlang 
> Foundation leadership has a clear direction/vision on this.
>
> So, how do we move forward?

First establish a usecase.
I would say that the ability to custom add static-analysis passes 
should be at the forefront, since that is what I would want a 
compiler as a library to do.

For Example, I want to be able to ask.

Forall functions in module a, give me the ones which call a 
function called malloc,
either directly or transitively, as far as you can see by the 
source code I gave you.
Forall functions which only exist as declarations (you don't have 
the body), create a list and cross reference it with the 
call-graph of the selection we've got before.

For that to work you need to be able to run time compiler until 
just before code-generation and you need to be able to walk that 
type/identifer-resolved tree in a useful manner.

Some kind of C plugin api would be preferred.