Initial data commit

Task/Call-a-foreign-language-function/Fortran/call-a-foreign-language-function.f

@@ -0,0 +1,45 @@
+module c_api
+    use iso_c_binding
+    implicit none
+
+    interface
+        function strdup(ptr) bind(C)
+            import c_ptr
+            type(c_ptr), value :: ptr
+            type(c_ptr) :: strdup
+        end function
+    end interface
+
+    interface
+        subroutine free(ptr) bind(C)
+            import c_ptr
+            type(c_ptr), value :: ptr
+        end subroutine
+    end interface
+
+    interface
+        function puts(ptr) bind(C)
+            import c_ptr, c_int
+            type(c_ptr), value :: ptr
+            integer(c_int) :: puts
+        end function
+    end interface
+end module
+
+program c_example
+    use c_api
+    implicit none
+
+    character(20), target :: str = "Hello, World!" // c_null_char
+    type(c_ptr) :: ptr
+    integer(c_int) :: res
+
+    ptr = strdup(c_loc(str))
+
+    res = puts(c_loc(str))
+    res = puts(ptr)
+
+    print *, transfer(c_loc(str), 0_c_intptr_t), &
+             transfer(ptr, 0_c_intptr_t)
+    call free(ptr)
+end program