D with minimal runtime

[IGotD-]

On Wednesday, 17 June 2020 at 02:09:47 UTC, dangbinghoo wrote:
>
> many pepole is requiring that the D runtime needs to be 
> minimal. Yes, this "is a linking problem" just if you're always 
> using "normal" or "rich" OS, things matter if you trying to 
> using D in the microcontroller target such as STM32F4 or 
> something similar, these platfrom has hundreds of KB ram and 
> maybe 1MB of flash memory, it's powerfull enogh for running the 
> D language.
>
> if you trying to build a betterC programing on these 
> platforms(only RTOS or no OS at all), it shows that D runtime 
> is requring some thing that only Rich-OS have.
>
> the rust and zig programming language is doing better in this 
> situation, the D runtime can be made only need to requiring 
> ANSI C stdlib (like nim 'any') and then the D runtime is more 
> portable.
>
>
> thanks!
> ----
> binghoo dang

Indeed and it is not only about "not linking in what you don't 
need" as the druntime expects a lot of things from the OS. This 
includes reading elf section information, which shouldn't be 
needed in a minimal system as we don't even know if the 
programmer wants to use elf/pe. Maybe the programmer just want to 
use a binary blob. Typically RTOS in small platforms like STM32F4 
or similar often don't implement TLS. For these kind of systems 
it would be nice if druntime didn't have any TLS variables at all 
and then the programmer must promise not to use any TLS 
variables. Essentially where you obtain the TLS area for each 
thread must be stubbed and just report empty TLS area.

Full D isn't really adapted for limited OS/RTOS today and it has 
painted itself into a corner by implementing a lot of expected OS 
support in the druntime. There isn't any wrong with it, it's just 
that D isn't a systems programming language and the question is 
if D should go that route. I'd say that D missed that train and D 
shouldn't peruse that any further.