Hi,

I am trying to compile D code to a shared library to be called by another language (in this case Julia). I can get a basic call to work but I can't call functions that use Phobos (I have no idea how to compile against it). I have found some documentation here and here that lists compilation against specific flags so for instance I have tried:

ldc2 jbasic.d -O3 -link-defaultlib-shared --betterC --boundscheck=off -nogc -shared -of=jbasic.so

But in Julia (and the equivalent thing happens in R), when I attempt to load the function I get an error:

ERROR: could not load library "./jbasic.so"
./jbasic.so: undefined symbol: _D3std6random__T21MersenneTwisterEngineTmVmi64Vmi312Vmi156Vmi31VmN5403634167711393303Vmi29Vmi6148914691236517205Vmi17Vmi8202884508482404352Vmi37VmN2270628950310912Vmi43Vmi6364136223846793005ZQGt6__initZ

I tried the equivalent with dmd:

dmd jbasic.d -O -defaultlib=libphobos2.so -betterC -fPIC -boundscheck=off  -shared -of=jbasic.so

with the same result.

Thank you.

On Monday, 31 May 2021 at 19:21:52 UTC, data pulverizer wrote:

The problem is almost certainly -betterC, which disables linking against Phobos and druntime.

On Monday, 31 May 2021 at 20:32:11 UTC, kinke wrote:

Thanks - I should have know that one! I've removed the flag but now I'm getting the following error when I try to call the function:

Aborting from src/core/time.d(2131) MonoTimeImpl!(ClockType.normal) failed to get the frequency of the system's monotonic clock.
signal (6): Aborted
in expression starting at REPL[2]:1
gsignal at x86_64-linux-gnu/libc.so.6 (unknown line)
abort at x86_64-linux-gnu/libc.so.6 (unknown line)
_D4core8internal5abortQgFNbNiNfMAyaMQemZv at /lib64/libphobos2.so.0.90 (unknown line)
_D4core4time__T12MonoTimeImplVEQBdQBb9ClockTypei0ZQBj8currTimeFNbNdNiNeZSQCtQCr__TQCpVQCei0ZQCz at dmd/current/lib64/libphobos2.so.0.90 (unknown line)
_D3std6random13bootstrapSeedFNbNiZm at dmd/current/lib64/libphobos2.so.0.90 (unknown line)
_D3std6random__T17unpredictableSeedTmZQwFNbNdNiNeZm at dmd/current/lib64/libphobos2.so.0.90 (unknown line)
_D3std6random17unpredictableSeedFNbNdNiNeZk at dmd/current/lib64/libphobos2.so.0.90 (unknown line)

On Monday, 31 May 2021 at 21:26:15 UTC, Steven Schveighoffer wrote:

Many thanks!

Something interesting is using arrays. I can see that if you instantiate an array within the D function using new, for instance

auto result = new double[n];

you can't return that array to Julia (or whatever) if your function does

scope(exit) Runtime.terminate();

and it segfaults. But while you can do:

auto result = cast(double*)malloc(double.sizeof * n);

you're left with the issue of not being able to free the memory since you've terminated the runtime.

So I guess you have to appropriately pair up initialize and terminate as appropriate to kind of startup and and shutdown the connection with druntime with your allocations if they stay within D?

On Monday, 31 May 2021 at 21:46:09 UTC, data pulverizer wrote:

Passing one of those to a C function is iffy anyway because the C function can hide it from the garbage collector.

What happens here is Runtime.terminate does a final GC sweep to gracefully clean up as much as it can before it close... and it thinks that array is unused, so it frees it.

GC.addRoot(array) can tell it not to free normally... but i'm not sure if runtime.terminate cares about that since terminate makes it think the whole thing is going down anyway.

you're left with the issue of not being able to free the memory since you've terminated the runtime.

You can free still, malloc and free are not controlled by the D runtime.

This is sometimes a better idea anyway when passing it to C function. I don't know how Julia does it though.

But yeah the best way to do it is to initialize once on library load then terminate once when the whole thing is finished.

Typically C plugin systems have some hook for this you can use. Like some onload function they define you can use or something.

Doing Runtime.initialize is working with Julia but not yet R, I'm getting a clock/GLIBC error

Error in dyn.load("rbasic.so") :
  unable to load shared object 'code/rbasic.so':
  lib/x86_64-linux-gnu/librt.so.1: undefined symbol: __clock_nanosleep, version GLIBC_PRIVATE

do I need to import anything else?