Linking ifort to g++ on Windows

[Beliavsky]

For normal_array.cpp

// https://people.duke.edu/~ccc14/sta-663-2018/notebooks/S12_CPP_Annotated.html

#include <random>
#include <functional> // needed for bind
extern "C" void normal_vec(int seed, int n, double x[]);

using std::default_random_engine,std::normal_distribution, std::bind;

void normal_vec(int seed, int n, double x[]) {
	// start random number engine with fixed seed
	default_random_engine re{seed};
	normal_distribution<double> norm(0,1); // mean and standard deviation
	auto rnorm = bind(norm, re);
	for (int i = 0; i<n; ++i) x[i] = rnorm();
}

 and xnormal.f90

program random_normal
use iso_c_binding
implicit none
!
interface
subroutine normal_vec(seed, n, x) bind(c)
import c_int, c_double
integer(kind=c_int), intent(in), value :: seed, n
real(kind=c_double)                    :: x(n)
end subroutine normal_vec
end interface
!
integer :: seed
integer, parameter :: n = 5
real(kind=c_double) :: x(n)
!
do seed=1,3
   call normal_vec(seed,n,x)
   print "(*(1x,f7.4))",x
end do
end program random_normal

I can compile and link on WSL2 with

g++ -c normal_array.cpp
ifort -c -o xnormal.o xnormal.f90
ifort normal_array.o xnormal.o

Trying that on Windows gives

normal_array.o : fatal error LNK1143: invalid or corrupt file: no symbol for COMDAT section 0x5

How should I compile and link on Windows?

[mecej4]

cl /std:c++17 /c normal_array.cpp
ifort xnormal.f90 normal_array.obj

[Beliavsky]

Thanks @mecej4 , that works for me, but I would still like to know how to do it with the g++ compiler.

[mecej4]

As Steve wrote, in general mixing objects from different compilers (in fact, compilers from different stables) will not work, because Ifort compiled objects will have dependencies on MS C/C++ libraries, and G++ compiled objects will depend on GNU libraries, with a lot of duplicated entry points between the two sets. 

In this rather simple example, there is only one entry point needed, and the following steps worked when I used Cygwin G++.

g++ -shared -fPIC normal_array.cpp -o normal_array.dll
lib /def:normal_array.def /machine:x64
ifort xnormal.f90 normal_array.lib

where normal_array.def contains

LIBRARY NORMAL_ARRAY.DLL
EXPORTS
normal_vec

You can reduce the size of the DLL by adding the option -s to the g++ command line.

[Steve_Lionel]

It may not be possible. You'd end up with a mix of g++ and MSVC library code in there, and bad things might happen. 

[Steve_Lionel]

Yes, isolating one or the other in a DLL is a good way to avoid some of these incompatibilities.