Status of WASM support?

[Sebastiaan Koppe]

On Saturday, 1 August 2020 at 08:42:49 UTC, Alexandru Ermicioi 
wrote:
> On Friday, 31 July 2020 at 21:18:25 UTC, Sebastiaan Koppe wrote:
>> I did experiment with a GC last year but I abandoned that in 
>> favor of porting druntime to wasm. The problems I ran into 
>> were mostly because 'new' isn't templated, so no amount of 
>> work I did would allow people to simply 'new' things, and 
>> instead they would always be stuck with custom allocators. 
>> Which is fine for some, but it is really barebones.
>
> I've been wondering, is it possible to make gc take an 
> allocator for memory allocation, instead of manually querying 
> OS for that?

Yep, that is what I am doing in the wasm port of druntime. 
Instead of querying memory from the OS it calls the appropriate 
wasm functions to increase memory (which function a lot like 
sbrk.)

The GC uses memory mapping to fetch and return memory. Wasm 
doesn't support it so I wrote a simple freelist on top of the 
wasm memory functions 
https://github.com/skoppe/druntime/blob/wasm/src/gc/os.d#L180 so 
that I could connect it to the GC (I can't use stdx allocator in 
druntime).

> If it is possible, then it would make possible to use new in 
> wasm, by just passing wasm allocator to it.

There is another problem with using 'new'. It isn't available in 
betterC, which means you need most of druntime first, before you 
can use it.