Nical wrote:
Hi, I'm trying to use C/C++ functions in a D program but I cant get
it to compile.
I tried the exemple of digital mars's website:
// ---- file.cpp
#include <iostream>
using namespace std;
int foo(int i, int j, int k)
{
cout << "i = " << i << endl;
cout << "j = " << j << endl;
cout << "k = " << k << endl;
return 7;
}
// ---- main.d
extern (C++) int foo(int i, int j, int k);
void main()
{
foo(1,2,3);
}
and a makefile that might not be correct now that i've experimented
various things on it:
OBJ= main.o file.o
all: ${OBJ}
g++ ${OBJ}
bin/main.o: file.o
dmd main.d
bin/file.o:
g++ -c file.cpp -o file.o
I get this error:
n...@nical-netbook:~/Programmation/D/test binding$ make
g++ -c -o file.o file.cpp
g++ main.o file.o -o test
/usr/lib/gcc/i486-linux-gnu/4.4.1/../../../../lib/crt1.o: In
function `_start':
/build/buildd/eglibc-2.10.1/csu/../sysdeps/i386/elf/start.S:115:
undefined reference to `main'
main.o: In function `no symbol':
main.d:(.text+0x8): undefined reference to `_Dmodule_ref'
collect2: ld returned 1 exit status
make: *** [all] Erreur 1
n...@nical-netbook:~/Programmation/D/test binding$
thanks in advance
Nico
The problem is that the linker doesn't find the main() function. I
think the following is what happens when you write a D program and
compile it with DMD:
1. You write a D-style main() function.
2. The D compiler automatically includes in the final executable
a C-style main() function that calls your D main(). This is
the actual starting point for your program, and the one the
linker is looking for.
g++ unfortunately doesn't include the C main() function, because it
doesn't know where to find it. There are thus two ways to solve your
problem:
a) Use DMD to link the files. You then have to explicitly pass it the
name of the C++ standard library as a linker option:
g++ -c file.cpp -o file.o
dmd -L-lstdc++ main.d file.o
b) Use g++ to link the files. You then have to explicitly pass it the
name and location of the D standard library and libpthread:
g++ -c file.cpp -o file.o
dmd -c main.d
g++ -L/path/to/D/library -lphobos2 -lpthread main.o file.o
I recommend a). Less typing. :)
-Lars
