D at 8-bit platform - some experiences

[kinke]

Thanks for the interesting write-up! :)

I haven't thought about what to do with size/ptrdiff_t and 
integer promotion rules for 8/16 bit targets yet. I guess the 
least surprising behavior would be mimicking gcc/clang there.

> Another big limitation on AVR isn't due to the bit width, but 
> it's Harvard architechture. LLVM considers pointers to program 
> memory a different type from data pointers, but LDC declares 
> function pointers as data pointers, resulting in LLVM type 
> error trying to compile their usage code.

Please file an LDC issue, fixing this shouldn't be rocket science.

> Third, you have the tools to make the object code as compact as 
> you want. For some reason, the linker doesn't recognise unused 
> functions by default, even with `-L--gc-sections` and 
> `--fvisibility=hidden`. I spent a long time fighting the 
> linker, once finally finding out that `--function-sections` 
> flag for the compiler is needed.

Both `--function-sections` and `-L--gc-sections` should be the 
default settings for bare-metal (and other) targets since LDC 
v1.32 - LDC was probably a bit too conservative in this regard 
before.