Requirement is to write some D code (which avoids the GC), that will be called from C.
So simple approach seemed to be to write D code under -betterC restrictions.

However, also need variable length arrays - but D Dynamic Arrays not allowed under -betterC.
So tried trivial example using std.container:

extern(C) void main() {

   import std.container;

   auto arr = Array!int(0, 2, 3);
}

compiled with:

dmd -betterC -run Array_ex_01v00

Which failed with:

C:\D\dmd2\windows\bin\..\..\src\druntime\import\core\internal\array\construction.d(207): Error: cannot use try-catch statements with -betterC
C:\D\dmd2\windows\bin\..\..\src\phobos\std\container\array.d(151): Error: template instance `core.internal.array.construction._d_arraysetctor!(const(Array!int)[], const(Array!int))` error instantiating
C:\D\dmd2\windows\bin\..\..\src\phobos\std\container\array.d(244):        instantiated from here: `RangeT!(const(Array!int))`
C:\D\dmd2\windows\bin\..\..\src\phobos\std\container\array.d(633):        instantiated from here: `RangeT!(Array!int)`
Array_ex_01v00.d(5):        instantiated from here: `Array!int`
C:\D\dmd2\windows\bin\..\..\src\druntime\import\core\internal\array\construction.d(207): Error: cannot use try-catch statements with -betterC
C:\D\dmd2\windows\bin\..\..\src\phobos\std\container\array.d(151): Error: template instance `core.internal.array.construction._d_arraysetctor!(immutable(Array!int)[], immutable(Array!int))` error instantiating
C:\D\dmd2\windows\bin\..\..\src\phobos\std\container\array.d(639):        instantiated from here: `RangeT!(immutable(Array!int))`
Array_ex_01v00.d(5):        instantiated from here: `Array!int`

Any ideas how to implement variable length arrays under -betterC?

On Monday, 17 April 2023 at 18:34:19 UTC, DLearner wrote:

You need a struct with operator overloads and libc realloc(), (very) basically

struct Array(T)
{
private:

    struct Payload
    {
        T* ptr;
        size_t length;
    }

    Payload p;

public:

    size_t length() {
        return p.length;
    }

    void length(size_t v) {
        import core.stdc.stdlib;
        p.ptr = cast(T*) realloc(p.ptr, v * T.sizeof);
    }

    ref T opIndex(size_t i) {
        return p.ptr[i];
    }
}

void main()
{
    Array!int a;
}

but you'll have to implement

• ctors
• concat assign
• slice assign
• copy construction
• value type elem alignment
• default elem construction
• default elem destruction
• etc.

to make that usable in on trivial cases.

Maybe try to find an already existing one;

https://github.com/gilzoide/betterclist
https://github.com/aferust/dvector
(maybe more in https://code.dlang.org/search?q=betterc)

On Monday, 17 April 2023 at 19:12:20 UTC, user456 wrote:

I understand from the thread this: D gives us -betterC but nothing from the Phobos. So he says, see what you have, do what the hell you want!

Am I wrong about this?

SDB@79