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digitalmars.D.learn - Using D within a rust codebase

reply powerboat9 <powerboat9.gamer gmail.com> writes:
I have an existing rust project, and I'm trying to rewrite part 
of it in D. However, I'm not sure how to get rust -> dlang 
interop working. I've looked into rust -> c -> dlang interop, but 
I'm not sure how to get c -> dlang interop working either.
Jul 26 2020
parent reply Paul Backus <snarwin gmail.com> writes:
On Sunday, 26 July 2020 at 21:18:19 UTC, powerboat9 wrote:

 I have an existing rust project, and I'm trying to rewrite part 
 of it in D. However, I'm not sure how to get rust -> dlang 
 interop working. I've looked into rust -> c -> dlang interop, 
 but I'm not sure how to get c -> dlang interop working either.


Here's the basic approach:

1. Write an `extern(C)` function in D.
2. Write a corresponding declaration of that function in C 
(typically, in a header file).
3. Use your D and C compilers to separately compile your D and C 
source files, respectively.
4. Use your D compiler to link the resulting object files.

For example, given these source files:

--- lib.d
extern(C) void hello()
{
	import std.stdio: writeln;
	writeln("Hello from D!");
}

--- lib.h
void hello();

--- main.c
#include "lib.h"

void main()
{
	hello();
}

...you can compile them with the following commands:





You should now be able run `./main` and see it print "Hello from 
D!"
Jul 26 2020
parent reply Jacob Carlborg <doob me.com> writes:
On 2020-07-27 03:03, Paul Backus wrote:


 extern(C) void hello()
 {
      import std.stdio: writeln;
      writeln("Hello from D!");
 }


The D runtime needs to be initialized first [1]. Then it should be 
terminated as well [2].

[1] https://dlang.org/phobos/core_runtime.html#.rt_init
[2] https://dlang.org/phobos/core_runtime.html#.rt_term

-- 
/Jacob Carlborg
Jul 27 2020
parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
On 7/27/20 3:50 AM, Jacob Carlborg wrote:> On 2020-07-27 03:03, Paul 
Backus wrote:

 extern(C) void hello()
 {
      import std.stdio: writeln;
      writeln("Hello from D!");
 }


 The D runtime needs to be initialized first [1]. Then it should be
 terminated as well [2].

 [1] https://dlang.org/phobos/core_runtime.html#.rt_init
 [2] https://dlang.org/phobos/core_runtime.html#.rt_term


They should be taken care of when the program is linked with a D compiler.

Otherwise, e.g. when the extern(C) code is part of a library written in 
D, one way of doing it is to add the following two functions to the 
library. (Typing by hand; may have typos).

import core.runtime;

pragma (crt_constructor)
extern (C)
int lib_init() {
   return Runtime.initialize() ? 0 : 1;
}

pragma (crt_destructor)
extern (C)
int lib_deinit() {
   return Runtime.terminate() ? 0 : 1;
}

Ali
Jul 27 2020
next sibling parent =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
On 7/27/20 4:43 AM, Ali =C3=87ehreli wrote:

 On 7/27/20 3:50 AM, Jacob Carlborg wrote:> On 2020-07-27 03:03, Paul=20



  > The D runtime needs to be initialized first [1]. Then it should be
  > terminated as well [2].
  >
  > [1] https://dlang.org/phobos/core_runtime.html#.rt_init


[...]


 pragma (crt_constructor)
 extern (C)
 int lib_init() {
  =C2=A0 return Runtime.initialize() ? 0 : 1;
 }


Ok, now I learned that my bool-to-int conversion is already taken care=20
of by rt_init(). Cool. :)

Ali
Jul 27 2020
prev sibling parent Jacob Carlborg <doob me.com> writes:
On 2020-07-27 13:43, Ali Çehreli wrote:


 They should be taken care of when the program is linked with a D compiler.


Just linking with a D compiler is not sufficient. There needs to be a D 
main function for the runtime to automatically be initialized. If you 
make the D code a bit more complicated, for example:

static this()
{
     import std.stdio: writeln;
     writeln("static this");
}

Then that won't be printed without a D main function or manually 
initializing the runtime.

The initial question was about linking D code into an already existing 
Rust code base. I don't think the first thing to try is to replace the 
Rust main function with a D main function.

-- 
/Jacob Carlborg
Jul 28 2020