add ABI check, improve C++ code and output check

Author: scivision

CMakeLists.txt

@@ -11,17 +11,12 @@
 cmake_minimum_required(VERSION 3.14)
 
 project(Fortran_C_CXX_interface
-LANGUAGES C Fortran CXX)
+LANGUAGES C Fortran CXX
+VERSION 1.1.0)
 
 include(CTest)
 
-if(CMAKE_Fortran_COMPILER_ID STREQUAL GNU)
-  # this helps show the options are/aren't conflicting between C and Fortran
-  # at build time
-  string(APPEND CMAKE_Fortran_FLAGS -fimplicit-none)
-endif()
-
-add_compile_options(-Wall)
+include (cmake/compilers.cmake)
 
 add_library(c_lib call_c.c)
 target_compile_features(c_lib PRIVATE c_std_99)
@@ -40,7 +35,7 @@ add_test(NAME CXXCallFortran COMMAND cxx_call_f)
 add_library(cxx_lib OBJECT call_cxx.cxx)
 target_compile_features(cxx_lib PRIVATE cxx_std_11)
 
-add_executable(f_call_cxx f_call_cxx.f90 $<TARGET_OBJECTS:cxx_lib>)
+add_executable(f_call_cxx f_call_c.f90 $<TARGET_OBJECTS:cxx_lib>)
 # LINKER_LANGUAGE option is necessary for ifort at least
 set_target_properties(f_call_cxx PROPERTIES LINKER_LANGUAGE Fortran)
 add_test(NAME FortranCallC++ COMMAND f_call_cxx)

c_call_f.f90

@@ -1,17 +1,17 @@
 module mytest
 
-use, intrinsic:: iso_c_binding, only: dp=>c_double, c_int
+use, intrinsic:: iso_c_binding, only: c_int, C_SIZE_T
 
 implicit none (type, external)
 
 contains
 
-pure subroutine timestwo(z,z2,N) bind(c)
+pure subroutine timestwo(z, z2, N) bind(c)
 ! elemental is not allowed with BIND(C)
 
-integer(c_int), intent(in) :: N
-real(dp),intent(in) :: z(N)
-real(dp),intent(out) :: z2(N)
+integer(C_SIZE_T), intent(in) :: N
+integer(c_int),intent(in) :: z(N)
+integer(c_int),intent(out) :: z2(N)
 
 z2 = 2*z
 

call_c.c

@@ -1,4 +1,4 @@
-void timestwo(double x[], double x2[], int N){
+void timestwo(int x[], int x2[], int N){
   for (int i=0; i<N; i++)
     x2[i] = x[i] * 2;
 }

call_cxx.cxx

@@ -3,7 +3,7 @@
 // nm libcxx.a
 // or whatever you name this library file.
 
-extern "C" void timestwo(double x[], double x2[], int N){
+extern "C" void timestwo(int x[], int x2[], int N){
   for (auto i=0; i<N; i++)
     x2[i] = x[i] * 2;
 }

cmake/abi_check/CMakeLists.txt

@@ -0,0 +1,6 @@
+cmake_minimum_required(VERSION 3.14)
+project(abi_check LANGUAGES C Fortran)
+
+add_library(addone OBJECT addone.c)
+
+add_executable(main main.f90 $<TARGET_OBJECTS:addone>)

cmake/abi_check/addone.c

@@ -0,0 +1,3 @@
+int addone(int N){
+  return N + 1;
+}

cmake/abi_check/main.f90

@@ -0,0 +1,17 @@
+program adder
+
+implicit none (type, external)
+
+interface
+integer function addone(N) bind(C)
+integer, intent(in), value :: N
+end function addone
+end interface
+
+
+if (addone(2) /= 3) error stop "unexpected addone result"
+
+print *, "OK: 2+1=3"
+
+
+end program

cmake/compilers.cmake

@@ -0,0 +1,18 @@
+# check C and Fortran compiler ABI compatibility
+
+try_compile(abi_ok ${CMAKE_CURRENT_BINARY_DIR}/abi_check ${CMAKE_CURRENT_LIST_DIR}/abi_check abi_check)
+if(abi_ok)
+  message(STATUS "C and Fortran compiler detected to be ABI-compatible.")
+else()
+  message(FATAL ERROR "C compiler {CMAKE_C_COMPILER_ID} {CMAKE_C_COMPILER_VERSION} and Fortran compiler ${CMAKE_Fortran_COMPILER_ID} ${CMAKE_Fortran_COMPILER_VERSION} are ABI-incompatible.")
+endif()
+
+
+if(CMAKE_Fortran_COMPILER_ID STREQUAL GNU)
+  # this helps show the options are/aren't conflicting between C and Fortran
+  # at build time
+  string(APPEND CMAKE_Fortran_FLAGS -fimplicit-none)
+  add_compile_options(-Wextra)
+endif()
+
+add_compile_options(-Wall)

cxx_call_f.cxx

@@ -1,22 +1,24 @@
 #include <iostream>
 #include <vector>
 
-extern "C" void timestwo(double [],double [],int*);
+extern "C" void timestwo(int [], int [], size_t*);
 
 
 int main()
 {
-  auto N = 3;
-  std::vector<double> x(N);
-  std::vector<double> x2(N);
 
-  for (auto i = 0; i < x.size(); i++)
-    x[i] = i;
+  std::vector<int> x = {0, 1, 2};
+  auto N = x.size();
+  std::vector<int> x2(N);
 
   timestwo(&x.front(), &x2.front(), &N);
 
-  for (auto i: x2)
-    std::cout << i << ' ';
+  for (auto i=0u; i < x2.size(); i++){
+    if (x2[i] != 2*x[i]){
+      fprintf(stderr, "value %d != %d", x2[i], x[i]);
+      return EXIT_FAILURE;
+    }
+  }
 
   return EXIT_SUCCESS;
 }

f_call_c.f90

@@ -1,25 +1,23 @@
 program call_c
-!! Demonstrate Fortran calling C.
+!! Demonstrate Fortran calling C or C++.
 !!
 !! Normally BIND(C) should be used after the function name in the interface block,
 !! rather than postpending underscore(s).
 
-use, intrinsic :: iso_c_binding, only: dp=>c_double, c_int
+use, intrinsic :: iso_c_binding, only: c_int
 implicit none (type, external)
 
 
 interface
-
-subroutine timestwo(x, x2, N)  bind (c)
-import c_int, dp
-integer(c_int), value :: N
-real(dp) :: x(N), x2(N)
+subroutine timestwo(a, a2, L)  bind (c)
+import c_int
+integer(c_int), value :: L
+integer(c_int) :: a(L), a2(L)
 end subroutine timestwo
-
 end interface
 
 integer(c_int) :: N, i
-real(dp), allocatable :: x(:), x2(:)
+integer(c_int), allocatable :: x(:), x2(:)
 
 N = 3
 

f_call_cxx.f90

@@ -15,7 +15,7 @@ f_call_c = executable('f_call_c', 'f_call_c.f90',
 test('Fortran calling C', f_call_c,  timeout: 10)
 
 cxx_lib = library('call_cxx', 'call_cxx.cxx')
-f_call_cxx = executable('f_call_cxx', 'f_call_cxx.f90',
+f_call_cxx = executable('f_call_cxx', 'f_call_c.f90',
   link_with: cxx_lib,
   link_language: 'fortran')
 test('Fortran calling C++', f_call_cxx, timeout: 10)