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LWDR (Light Weight D Runtime) for Microcontrollers v0.2.3
May 30
Dukc
May 30

Github: https://github.com/0dyl/LWDR
DUB: https://code.dlang.org/packages/lwdr

Hi, all!
This is LWDR (Light Weight D Runtime) It is a ground-up implementation of a D runtime targeting the ARM Cortex-M microcontrollers and other microcontroller platforms with RTOSes (Real Time Operating Systems).

It doesn't, and possibly may not, support all D features in order to make it viable for the constrained environments. For example, all memory allocation is manually done via new and delete - no GC.

It works by providing a series of barebones API hooks (alloc, dealloc, assert, etc) (defined in rtoslink.d), which you must implement and/or point to your RTOS implementation.

It can be compiled with either GDC or LDC and it is DUB compatible.

It has so far been successfully run on a real STM32F407.

LWDR currently supports the following language features:

  • Class allocations and deallocations (via new and delete)
  • Struct heap allocations and deallocations (via new and delete)
  • Invariants
  • Asserts
  • Contract programming
  • Basic RTTI (via TypeInfo stubs)
  • Interfaces
  • Static Arrays
  • Virtual functions and overrides
  • Abstract classes
  • Static classes
  • Allocation and deallocation of dynamic arrays
  • Concatenate an item to a dynamic array
  • Concatenate two dynamic arrays together
  • Dynamic array resizing

The following features are experimental:

  • Exceptions and Throwables (so far are working on GDC only)

Not supported:

  • Module constructors and destructors
  • ModuleInfo
  • There is no GC implementation
  • TLS (thread local static) variables
  • Delegates/closures
  • Associative arrays
  • Shared/synchronized
  • Object hashing
  • Other stuff I have forgotten :(

It is beta, so expect bugs.

May 30

On Sunday, 30 May 2021 at 14:28:25 UTC, Dylan Graham wrote:

>

Github: https://github.com/0dyl/LWDR
DUB: https://code.dlang.org/packages/lwdr

I added a Wiki tutorial on compiling with LDC and DUB (which is how I currently test LWDR). It's about 12:53 AM AEST, so I'm heading to bed. I plan on adding more usage and compilation tutorials in the future.

I've made a tonne of progress on this project in just a few hours, so I'm pretty happy, I hope you'll like it too!

May 30

Nice job!

Are you tried compile apps with Phobos?

May 30

On Sunday, 30 May 2021 at 14:28:25 UTC, Dylan Graham wrote:

>

LWDR currently supports the following language features:

  • Class allocations and deallocations (via new and delete)
  • Struct heap allocations and deallocations (via new and delete)
  • Invariants
  • Asserts
  • Contract programming
  • Basic RTTI (via TypeInfo stubs)
  • Interfaces
  • Static Arrays
  • Virtual functions and overrides
  • Abstract classes
  • Static classes
  • Allocation and deallocation of dynamic arrays
  • Concatenate an item to a dynamic array
  • Concatenate two dynamic arrays together
  • Dynamic array resizing

The following features are experimental:

  • Exceptions and Throwables (so far are working on GDC only)
>

It is beta, so expect bugs.

Nice job!

May 30

On Sunday, 30 May 2021 at 14:28:25 UTC, Dylan Graham wrote:

>

Github: https://github.com/0dyl/LWDR
DUB: https://code.dlang.org/packages/lwdr

Hi, all!
This is LWDR (Light Weight D Runtime) It is a ground-up implementation of a D runtime targeting the ARM Cortex-M microcontrollers and other microcontroller platforms with RTOSes (Real Time Operating Systems).

It doesn't, and possibly may not, support all D features in order to make it viable for the constrained environments. For example, all memory allocation is manually done via new and delete - no GC.

It works by providing a series of barebones API hooks (alloc, dealloc, assert, etc) (defined in rtoslink.d), which you must implement and/or point to your RTOS implementation.

It can be compiled with either GDC or LDC and it is DUB compatible.

It has so far been successfully run on a real STM32F407.

LWDR currently supports the following language features:

  • Class allocations and deallocations (via new and delete)
  • Struct heap allocations and deallocations (via new and delete)
  • Invariants
  • Asserts
  • Contract programming
  • Basic RTTI (via TypeInfo stubs)
  • Interfaces
  • Static Arrays
  • Virtual functions and overrides
  • Abstract classes
  • Static classes
  • Allocation and deallocation of dynamic arrays
  • Concatenate an item to a dynamic array
  • Concatenate two dynamic arrays together
  • Dynamic array resizing

The following features are experimental:

  • Exceptions and Throwables (so far are working on GDC only)

Not supported:

  • Module constructors and destructors
  • ModuleInfo
  • There is no GC implementation
  • TLS (thread local static) variables
  • Delegates/closures
  • Associative arrays
  • Shared/synchronized
  • Object hashing
  • Other stuff I have forgotten :(

It is beta, so expect bugs.

Great work!

May 30

On Sunday, 30 May 2021 at 14:28:25 UTC, Dylan Graham wrote:

>

Hi, all!
This is LWDR (Light Weight D Runtime) It is a ground-up implementation of a D runtime targeting the ARM Cortex-M microcontrollers and other microcontroller platforms with RTOSes (Real Time Operating Systems).

Sounds very useful! However, first thing first: What's the license? DUB package says it's FOSS. Great, but what kind of FOSS? It makes a big difference whether it's GNU or BSD, for instance.

>

It doesn't, and possibly may not, support all D features in order to make it viable for the constrained environments. For example, all memory allocation is manually done via new and delete - no GC.

Regarding new - is there a good way to iterate though chunks allocated with new? One could call an unmodified piece of D code that normally uses the GC, and then manually free all it's allocations.

>

It works by providing a series of barebones API hooks (alloc, dealloc, assert, etc) (defined in rtoslink.d), which you must implement and/or point to your RTOS implementation.

Quickly looking, the implementation looks very portable, save for exceptions. with rtoslink.d, this will probably enable a lot of stuff on any platform without DRuntime. Not just microcontrollers. If I'm right, you just did a BIG service for D on bare-metal.

>

It is beta, so expect bugs.

And open source, so the bugs can be fixed as discovered :-). Thanks for the warning anyway.

May 30

On Sunday, 30 May 2021 at 15:07:54 UTC, Denis Feklushkin wrote:

>

Nice job!

Are you tried compile apps with Phobos?

Thank you!

No, I haven't tried any of Phobos yet. It should work, but will leak like a sieve.

I need to develop a solution that tracks memory allocations and exposes a simplified interface to the user for deletion.

May 30

On Sunday, 30 May 2021 at 15:35:34 UTC, Guillaume Piolat wrote:

>

On Sunday, 30 May 2021 at 14:28:25 UTC, Dylan Graham wrote:

>

LWDR currently supports the following language features:

  • Class allocations and deallocations (via new and delete)
  • Struct heap allocations and deallocations (via new and delete)
  • Invariants
  • Asserts
  • Contract programming
  • Basic RTTI (via TypeInfo stubs)
  • Interfaces
  • Static Arrays
  • Virtual functions and overrides
  • Abstract classes
  • Static classes
  • Allocation and deallocation of dynamic arrays
  • Concatenate an item to a dynamic array
  • Concatenate two dynamic arrays together
  • Dynamic array resizing

The following features are experimental:

  • Exceptions and Throwables (so far are working on GDC only)
>

It is beta, so expect bugs.

Nice job!

Thank you all for a kind words :D

May 31

On Sunday, 30 May 2021 at 17:31:37 UTC, Dukc wrote:

>

On Sunday, 30 May 2021 at 14:28:25 UTC, Dylan Graham wrote:

>

Hi, all!
This is LWDR (Light Weight D Runtime) It is a ground-up implementation of a D runtime targeting the ARM Cortex-M microcontrollers and other microcontroller platforms with RTOSes (Real Time Operating Systems).

Sounds very useful! However, first thing first: What's the license? DUB package says it's FOSS. Great, but what kind of FOSS? It makes a big difference whether it's GNU or BSD, for instance.

I haven't put any thought into the license. Since LWDR is derived from DRuntime, I assume I'll have to use its license. If not, I'd like to go with something permissive like MIT.

> >

It doesn't, and possibly may not, support all D features in order to make it viable for the constrained environments. For example, all memory allocation is manually done via new and delete - no GC.

Regarding new - is there a good way to iterate though chunks allocated with new? One could call an unmodified piece of D code that normally uses the GC, and then manually free all it's allocations.

Bingo. I was thinking of thread-local tracking of allocations. Something like follows:

Impl:

size_t numAllocations = 0;
List!(void*) allocations;

    void* allocateMemoryForNew(int size)
    {
        numAllocations++;
        auto ptr = rtosbackend_heapalloc(size);
        allocations.add(ptr);
        return allocations;
    }
    void deallocateMemory(void* ptr)
    {
        allocations.removeLastOccurenceOf(ptr);
        numAllocations--;
        rtosbackend_heapfreealloc(ptr);
    }

    struct MemAlloc
    {
        size_t allocs;

        void free() {
            // allocs should be less than numAllocations,
            // so delete the last n items of allocations

            auto difference = numAllocations - allocs;
            foreach(i; 0 .. difference) {
                auto ptr = allocations[allocations.length - i]; // get ith to last
                deallocateMemory(ptr);
            }
        }
    }

    MemAlloc enterTrackedMemory()
    {
        return MemAlloc(.numAllocations);
    }

Usage:

auto mem0 = enterTrackedMemory(); // mem0 says that there should be 0 allocations
A a = new A(); // 1 allocation
{
    auto mem1 = enterTrackedMemory(); // mem1 says that there should be 1 allocations total
    auto b = new A(); // 1 allocation, so total is now 2
    mem1.free; // we need to get back to 1 allocation, so delete b (most recent allocation)
}
mem0.free; // delete everything

This works with scope(...).

There's some caveats with this - if a phobos function calls a user function, anything that user function allocates will be wiped, too (may or may not be desirable behaviour), unless some protocol for opting out of tracking is implemented.

> >

It works by providing a series of barebones API hooks (alloc, dealloc, assert, etc) (defined in rtoslink.d), which you must implement and/or point to your RTOS implementation.

Quickly looking, the implementation looks very portable, save for exceptions. with rtoslink.d, this will probably enable a lot of stuff on any platform without DRuntime. Not just microcontrollers. If I'm right, you just did a BIG service for D on bare-metal.

Exceptions are a nightmare. It works for GDC with GCC code. My codebase uses GCC for its C (ST toolchain), so I need to write some code that can take LDC's exception handling and make it compatible with how GCC operates. So, it looks like there will be multiple exception handling implementations (LDC with GCC backend, LDC with clang backend, GDC with GCC backend). I wish D had something like Zig's error handling.

Otherwise, thank you! It was designed to be agnostic as much as possible. I didn't know it'd help out for more than just microcontrollers :)

May 31

On Sunday, 30 May 2021 at 14:28:25 UTC, Dylan Graham wrote:

>

Github: https://github.com/0dyl/LWDR
DUB: https://code.dlang.org/packages/lwdr

As for my next steps, I'm going to look at implementing TLS variables. It doesn't look too difficult.

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