On Friday, 16 October 2020 at 03:42:22 UTC, Adam D. Ruppe wrote:
On Friday, 16 October 2020 at 03:04:25 UTC, Jack wrote:
How can I allocate memory for this class?
It is possible but not easy without druntime.
If you are using -betterC, you can use extern(C++) classes with
extern(D) members. The compiler will let you declare that. But
then you need to allocate it. `__traits(classInstanceSize,
Whatever)` will tell you the size to malloc, but you also need
to copy an initializer over before you call the constructor.
I have a technique here that works on dmd...
http://dpldocs.info/this-week-in-d/Blog.Posted_2020_07_27.html#zero-runtime-classes
I did consider do something like this but the class would only
live in the function's lifetime, right? that wouldn't work if I
need to pass the class around
but ldc is more strict about the type definition and I don't
know the magic it expects there... like it should be doable but
idk how so this might not be of much use.
Which type definition are you refering to? you mean the class
members/memory layout of a class?
Personally, I prefer to just not use betterC and make my own
mini runtime:
I was thinking the same, this seems the way to go.
http://dpldocs.info/this-week-in-d/Blog.Posted_2020_08_10.html
in particular
This is great! I'll try write a small druntime too for my case.
Do you have links/resources where things like __heap_base,
__data_end are defined? assuming there's such documentation
somewhere, if you did into the compiler to get those, let me know
where you can it too. I didn't understand the interation of
webassembly-core.js with D. for example, you have this:
// placeholder to be filled in by the loader
var memory;
How did you put the compiler/linker to set memory's location
properly so you can do things like:
memorySize: function() { return memory.buffer.byteLength; },
?
in the same way that ldc defines __headp_base and __data_end,
doesn't it define some variables where the implementation of
memorySize() and growMemory() could be done in D? also, where can
I find this Sebastiaan's project that you mentioned in the
article? it's a druntime like yours?
https://github.com/adamdruppe/webassembly/blob/master/arsd-webassembly/object.d#L74
this is great, good enough to put me in the direction on how to
do that. Also, I found C++ has this EMSCRIPTEN_BINDINGS() from
emscripten/bind.h header, see[1] for example. I haven't tried
yet. But maybe marking the class as extern(C) that would work
with D's class too, right? I don't know about the C++'s or
compiler's dependences that would prevent it from working with D.
In fact, that seems quite a hacky. Do you think we are better off
write our own small druntime? if I got an working nice one, I'll
put on github for those who would like to use this.
[1]:
https://stackoverflow.com/questions/15865923/interaction-with-c-classes-in-emscripten
Thanks for your answer, that was really helpful.
But that's also not easy, lots of unfinished cases in my thing,
but I did manage to make it work... for my specific case.
