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digitalmars.D - Linking C++ with a D-library

reply "Milvakili" <maliy.kayit gmail.com> writes:
Hi, I'm a new to D and I could not find any relevant answers in 
the forum.

I want to call functions from D-lib from c++ main.
dlibrary

import std.stdio;

extern (C++) void foo(int i, int j, int k) {
   writefln("i = %s", i);
   writefln("j = %s", j);
   writefln("k = %s", k);
}
void main(){}


c++ binary

#include <iostream>

void CXXmain();
void foo(int i, int j, int k);
using namespace std;

int main(){
   cout << "This is the main of C++\n";
   foo(1,3,4);
   return 0;
}


I can compile d with dmd and c++ with g++ then linked them with 
g++.  The problem is when I run the binary I got:


 ./runtest


This is the main of C++
Segmentation Fault

I could not figure out the problem.  And when I call the C++ 
functions from the main of D everything works.  So why have I 
segmentation when I call the main from C++.
Jun 26 2013
parent reply "Adam D. Ruppe" <destructionator gmail.com> writes:
On Wednesday, 26 June 2013 at 20:19:07 UTC, Milvakili wrote:

 Hi, I'm a new to D and I could not find any relevant answers in 
 the forum.

 I want to call functions from D-lib from c++ main.
 dlibrary

 import std.stdio;

 extern (C++) void foo(int i, int j, int k) {
   writefln("i = %s", i);
   writefln("j = %s", j);
   writefln("k = %s", k);
 }
 void main(){}



Try adding this to D:

extern(C) void initialize_D() {
   import core.runtime;
   Runtime.initialize();
}



And this to C++:


 void foo(int i, int j, int k);


extern "C" void initialize_d();


 using namespace std;

 int main(){


     initialize_d();


   cout << "This is the main of C++\n";
   foo(1,3,4);
   return 0;
 }



And you should see something better.
Jun 26 2013
parent reply "Milvakili" <maliy.kayit gmail.com> writes:
On Wednesday, 26 June 2013 at 20:23:35 UTC, Adam D. Ruppe wrote:

 On Wednesday, 26 June 2013 at 20:19:07 UTC, Milvakili wrote:

 Hi, I'm a new to D and I could not find any relevant answers 
 in the forum.

 I want to call functions from D-lib from c++ main.
 dlibrary

 import std.stdio;

 extern (C++) void foo(int i, int j, int k) {
  writefln("i = %s", i);
  writefln("j = %s", j);
  writefln("k = %s", k);
 }
 void main(){}



 Try adding this to D:

 extern(C) void initialize_D() {
   import core.runtime;
   Runtime.initialize();
 }



 And this to C++:


 void foo(int i, int j, int k);


 extern "C" void initialize_d();


 using namespace std;

 int main(){


     initialize_d();


  cout << "This is the main of C++\n";
  foo(1,3,4);
  return 0;
 }



 And you should see something better.


That "magically" solves my problem.  Would you mind if I ask you 
to define what this initialization is all about or guide me to 
some tutorial related to these issues?

Thanks alot.
Jun 26 2013
parent reply Justin Whear <justin economicmodeling.com> writes:
On Wed, 26 Jun 2013 22:32:55 +0200, Milvakili wrote: 

 That "magically" solves my problem.  Would you mind if I ask you to
 define what this initialization is all about or guide me to some
 tutorial related to these issues?
 
 Thanks alot.


The function initializes the D runtime library.  I believe the 
initialization must be done primarily due to the garbage collector, but 
there's a list of what the runtime provides in the readme here: https://
github.com/D-Programming-Language/druntime
Jun 26 2013
parent reply "Milvakili" <maliy.kayit gmail.com> writes:
On Wednesday, 26 June 2013 at 20:37:25 UTC, Justin Whear wrote:

 On Wed, 26 Jun 2013 22:32:55 +0200, Milvakili wrote:

 That "magically" solves my problem.  Would you mind if I ask 
 you to
 define what this initialization is all about or guide me to 
 some
 tutorial related to these issues?
 
 Thanks alot.


 The function initializes the D runtime library.  I believe the
 initialization must be done primarily due to the garbage 
 collector, but
 there's a list of what the runtime provides in the readme here: 
 https://
 github.com/D-Programming-Language/druntime


Great!
Jun 26 2013
parent reply "Adam D. Ruppe" <destructionator gmail.com> writes:
I think specifically for writefln it needs to grab module 
constructors from the initialization, to set up the output 
stream. The GC and typeinfo would be important for a longer 
example.

You might also want to do something similar at the end of C++'s 
main with Runtime.terminate().
Jun 26 2013
parent reply "Milvakili" <maliy.kayit gmail.com> writes:
On Wednesday, 26 June 2013 at 21:12:26 UTC, Adam D. Ruppe wrote:

 I think specifically for writefln it needs to grab module 
 constructors from the initialization, to set up the output 
 stream. The GC and typeinfo would be important for a longer 
 example.

 You might also want to do something similar at the end of C++'s 
 main with Runtime.terminate().


Thanks.

What about the other way around. If I linked them with dmd in 
that case it throws errors due to <iostream>, what should I do in 
that case?
Jun 26 2013
parent "Adam D. Ruppe" <destructionator gmail.com> writes:
On Thursday, 27 June 2013 at 00:00:23 UTC, Milvakili wrote:

 What about the other way around. If I linked them with dmd in 
 that case it throws errors due to <iostream>, what should I do 
 in that case?


I don't think you need to do any special C++ initialization, any 
needed work there is automatically inserted by the linker.

Just make sure you link with -L-lstdc++ if you're linking with 
dmd on Linux and the needed c++ lib should be pulled in.

Or if you want to link with g++ or ld, you'll want to link in 
-lphobos2 to get the D standard library.

Running dmd -v can be helpful to see exactly what is going on:

$ dmd -v test.d
< snip a lot of stuff >
gcc test25.o -o test25 -m32 
-L/home/me/d/dmd2/linux/bin32/../lib32 
-L/home/me/d/dmd2/linux/bin32/../lib64 -Xlinker 
--no-warn-search-mismatch -Xlinker --export-dynamic 
-l:libphobos2.a -lpthread -lm -lrt
$


Right at the end, you can see the command dmd is running to do 
the link. It uses gcc here, passing a bunch of libraries D will 
need.



But if you just let dmd do the link you can add C++ libraries 
with -L-l.
Jun 26 2013