On Wednesday, 16 September 2020 at 17:59:41 UTC, Remi wrote:
I tried to modify the hello.d example from your blog post. It works without changes but when I tried to do a string concatenation
Yeah, concatenation is one of the features that uses druntime, and specifically, it is done through TypeInfo. I would actually personally skip it if you are doing a minimal custom thing.
If you skip it, you can implement your own type instead of using the built-in array concat. You can make a struct with an operator overload to look basically the same, and it can give a slice to pass to other functions. This is much easier here - no druntime code needed and the user code will be clearer that they might have to manage the memory. Typical code with normal append tends to just assume there's no stomping, that the GC takes care of it, etc.
I'm hitting linker errors related to TypeInfo:
But if you do implement it, as of right now, you have to define TypeInfo. Which suckssssss because it is super tedious. There's a WIP pull request up there with dmd to templatize this which would help a lot. But right now it means implementing at least some of it.
You'd need the base class TypeInfo, then TypeInfo_a (a == "char"), TypeInfo_Array, TypeInfo_Aa (which means "array of char"), then finally, TypeInfo_Aya, which is "array of immutable char", aka, string.
Once you get enough of that up - and the compiler is picky about those right now - then the append operation is `_d_arrayappendcTX`, which takes TypeInfo as a param.
Search these names in the druntime source to see their official implementations... it is a bit of a beast, which is why I recommend actually skipping them if you can. It quickly explodes in size and by the time you follow it to its final conclusion, you've reimplemented 3/4 of full druntime anyway and might as well have just done a port.
