Embedded Systems (STM32) LDC Absolute minimal runtime

[Mike via Digitalmars-d]

On Monday, 19 June 2017 at 10:24:29 UTC, Dan Walmsley wrote:

> I have played around with the betterC flag and it looks 
> promising. I would also like to have use of classes, however as 
> soon as I try to use a class I get many link errors. see below:

It is my understanding that the DMD -betterC switch currently 
only disables generating ModuleInfo.  Walter's recent pull 
request 
(http://forum.dlang.org/post/oi9v2q$23ms$1@digitalmars.com) makes 
it do a little more.

It is also my understanding the -betterC is just an idea at the 
moment, and what it should do has not yet been defined.

>
> The  undefined reference to `_d_dso_registry' comes from 
> removing the -betterC flag.
>
> I understand these other symbols would be provided by object.d, 
> however I am unable to find an object.d that will compile on 
> LDC, and ideally a minimal implementation.

The most minimal implementation I'm aware of is this: 
https://wiki.dlang.org/Minimal_semihosted_ARM_Cortex-M_%22Hello_World%22

If you're targeting STM32, you may also be interested in this: 
https://github.com/JinShil/stm32f42_discovery_demo

I haven't tested either of those in quite some time, so I doubt 
the will compile out of the box.  But basically, what you need is 
a minimal runtime implementation that implements the features of 
D that your code is using, and unfortunately, some that your code 
isn't using but is required by the compiler just to get a build.

> C:\dev\repos\STM32DBlinky\Blinky\build\obj\main.o: In function 
> `_D4main9TestClass3SumMFZi':
> C:\dev\repos\STM32DBlinky\Blinky/main.d:9: undefined reference 
> to `_D9invariant12_d_invariantFC6ObjectZv'
> C:\dev\repos\STM32DBlinky\Blinky/main.d:9: undefined reference 
> to `_d_assert_msg'
> C:\dev\repos\STM32DBlinky\Blinky\build\obj\main.o: In function 
> `ldc.register_dso':
> C:\dev\repos\STM32DBlinky\Blinky\main.d:(.text.ldc.register_dso+0x60): undefined reference to `_d_dso_registry'
> C:\dev\repos\STM32DBlinky\Blinky\build\obj\main.o:(.data.rel.ro._D4main9TestClass6__vtblZ[_D4main9TestClass6__vtblZ]+0x4): undefined reference to `_D6object6Object8toStringMFZAya'
> C:\dev\repos\STM32DBlinky\Blinky\build\obj\main.o:(.data.rel.ro._D4main9TestClass6__vtblZ[_D4main9TestClass6__vtblZ]+0x8): undefined reference to `_D6object6Object6toHashMFNbNeZk'
> C:\dev\repos\STM32DBlinky\Blinky\build\obj\main.o:(.data.rel.ro._D4main9TestClass6__vtblZ[_D4main9TestClass6__vtblZ]+0xc): undefined reference to `_D6object6Object5opCmpMFC6ObjectZi'
> C:\dev\repos\STM32DBlinky\Blinky\build\obj\main.o:(.data.rel.ro._D4main9TestClass6__vtblZ[_D4main9TestClass6__vtblZ]+0x10): undefined reference to `_D6object6Object8opEqualsMFC6ObjectZb'
> C:\dev\repos\STM32DBlinky\Blinky\build\obj\main.o:(.data._D4main9TestClass7__ClassZ[_D4main9TestClass7__ClassZ]+0x0): undefined reference to `_D14TypeInfo_Class6__vtblZ'
> C:\dev\repos\STM32DBlinky\Blinky\build\obj\main.o:(.data._D4main9TestClass7__ClassZ[_D4main9TestClass7__ClassZ]+0x28): undefined reference to `_D6Object7__ClassZ'

`_d_assert_msg` and `_d_dso_registry` and those symbols with 
`_d_invariant` in them look like missing druntime 
implementations.  You can see an old and unmaintained list of 
such "runtime hooks" here: https://wiki.dlang.org/Runtime_Hooks.  
Each compiler (DMD, LDC, and GDC) have their own druntime 
implementation, unfortunately.  LDC's implementation is here: 
https://github.com/ldc-developers/druntime

I suspect the `.data.re.ro.*` symbols are the result of an error 
in your linker script.  That is you haven't added that `.data` 
section to your linker script, so the symbols aren't being 
populated.  I'd have to see your linker script and source code 
before I spend to much mental energy on it, though.

No compiler that I'm aware has a druntime implementation for the 
ARM Cortex-M architecture, so the onus is on you to build 
implement whatever features the toolchain is complaining about.

Mike