From f1641dd4e4178da0fb6aac2a6a41fe848b11ba51 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20Coppens?= <francois.coppens@uvsq.fr>
Date: Thu, 4 Feb 2021 17:05:55 +0100
Subject: [PATCH] Solved linking problem by including C++ standard library
 '-lstdc++'. Also added a minimal working example of Fortran-C++ interfacing
 in dir 'mwe'.

---
 Makefile       | 14 ++++++++------
 mwe/compile.sh |  1 +
 mwe/main.f90   | 12 ++++++++++++
 mwe/worker.cpp |  7 +++++++
 mwe/worker.h   |  6 ++++++
 5 files changed, 34 insertions(+), 6 deletions(-)
 create mode 100755 mwe/compile.sh
 create mode 100644 mwe/main.f90
 create mode 100644 mwe/worker.cpp
 create mode 100644 mwe/worker.h

diff --git a/Makefile b/Makefile
index cf37720..cb48a63 100644
--- a/Makefile
+++ b/Makefile
@@ -1,8 +1,8 @@
-CXX=icpc
-CXXFLAGS=-O0 -debug full -traceback
-FC=ifort
-FFLAGS=-O0 -debug full -traceback
-# ARCH=-xCORE-AVX2 
+CXX = icpc
+CXXFLAGS = -O0 -debug full -traceback
+FC = ifort
+FFLAGS = -O0 -debug full -traceback
+# ARCH = -xCORE-AVX2 
 
 ## Deps & objs for the C++ stuff
 cppDEPS = cppmain.cpp SM_MaponiA3.cpp SM_MaponiA3.hpp Helpers.hpp
@@ -11,6 +11,8 @@ cppOBJ = cppmain.o SM_MaponiA3.o
 ## Deps & objs for the Fortran stuff
 fDEPS = fmain.f90 SM_MaponiA3_mod.f90
 fOBJ = SM_MaponiA3.o SM_MaponiA3_mod.o fmain.o
+fLIBS = -lstdc++
+
 
 ## Compile recipes for C++ stuff
 %.o: %.cpp $(cppDEPS)
@@ -36,4 +38,4 @@ cppSherman-Morrison: $(cppOBJ)
 
 ## Linking Fortran example program calling the C++ function 'Sherman_Morrison()'
 fSherman-Morrison: $(fOBJ)
-	$(FC) $(ARCH) $(FFLAGS) -o $@ $^
+	$(FC) $(ARCH) $(FFLAGS) $(fLIBS) -o $@ $^
diff --git a/mwe/compile.sh b/mwe/compile.sh
new file mode 100755
index 0000000..72b5010
--- /dev/null
+++ b/mwe/compile.sh
@@ -0,0 +1 @@
+icpc -c worker.cpp && ifort -c main.f90 && ifort -lstdc++ worker.o main.o -o test
diff --git a/mwe/main.f90 b/mwe/main.f90
new file mode 100644
index 0000000..4d9a8e1
--- /dev/null
+++ b/mwe/main.f90
@@ -0,0 +1,12 @@
+program test
+  use iso_c_binding
+  implicit none
+
+  interface
+    subroutine hello() bind(C, name="worker")
+    end subroutine
+  end interface
+
+  call hello()
+
+end program test
diff --git a/mwe/worker.cpp b/mwe/worker.cpp
new file mode 100644
index 0000000..1b678b8
--- /dev/null
+++ b/mwe/worker.cpp
@@ -0,0 +1,7 @@
+#include "worker.h"
+
+void worker()
+{
+  std::cout << "Hello, World!" << std::endl;
+}
+
diff --git a/mwe/worker.h b/mwe/worker.h
new file mode 100644
index 0000000..70ff209
--- /dev/null
+++ b/mwe/worker.h
@@ -0,0 +1,6 @@
+#include <iostream>
+
+extern "C"
+{
+  void worker();
+}