Hitchikers Guide to Porting Phobos / D Runtime to other architectures

[Adam D. Ruppe]

On Wednesday, 8 January 2014 at 00:21:15 UTC, Mike wrote:
> I'm sorry I can't share my code at the moment; I haven't 
> decided yet where to put it.  I was studying Adam Ruppe's 
> minimal X86 port last night and found it most useful (Thumbs 
> Up!), but with a 2000 line object.d, it's stretching the word 
> "minimal", at least when compared with C. But if you really 
> want all the cool stuff D has to offer, this is probably what 
> will be required in the end.

Sorry if I'm late to reply, I'm barely following this thread, 
just poking in when I see me mentioned :)

But I started with a truly minimal D: the standalone file here 
was my first go <http://arsdnet.net/dcode/minimal.d> but indeed, 
that hits limits fast. I'd be ok with it as a "better C"... and 
the 3KB statically linked elf executable was awesome, but not 
even structs work, which takes a lot of fun out of things.

So I started adding stuff. Note that about 500 lines of the 
object.d in there aren't strictly needed, but since I had a 
custom druntime, I wanted to play a bit :)

Some things are needed so the compiler doesn't complain. Some 
stuff, typeinfo especially, are there so the linker doesn't 
complain.

Then classes and exceptions were a lot of code (which I 
copy/pasted from druntime). About line 900 - line 2000 are these. 
You could cut a *lot* of that out if you didn't want to use 
exceptions, but I like them so I wanted that to work. But 
exceptions need stack unwinding (BTW gdc uses a totally different 
stack unwinding thing, at least on ARM/raspberry pi. This is 
dmd's code) and classes so it kinda ballooned the size a bit.

I just fixed this to work with newer dmd btw.
http://arsdnet.net/dcode/minimal.zip

The executable was ~30 KB statically linked, and a good majority 
of the language worked. So I was pretty happy with that trade 
off. A lot of lines, but not a huge amount of bloat.



Anywho, let me get it back to the whole "minimal" thing....

But put a single struct and it complains
Error: TypeInfo not found. object.d may be incorrectly installed 
or corrupt, compile with -v switch


even with -betterC :-( :-( :-(


I don't even care about typeinfo; doing my own runtime, I'd be ok 
with any function that needs it to simply fail to compile. I can 
do it myself with templates.

Basic structs should really work regardless.


> Even the switch...case statement seems to be, at least 
> partially, implemented in the runtime

Yea, for strings. My thing did a stupid loop for string cases :P

If you don't try to use a string switch though, those references 
aren't emitted at all.