add C=>Fortran struct

Author: scivision

src/CMakeLists.txt

@@ -25,6 +25,10 @@ add_test(NAME C_Fortran_error
   COMMAND ${CMAKE_COMMAND} -Dexe=$<TARGET_FILE:c_fortran_error> -Dexp_code=42 -P ${PROJECT_SOURCE_DIR}/cmake/test_error.cmake
 )
 
+add_executable(c_fortran_struct c/struct_main.c)
+target_link_libraries(c_fortran_struct PRIVATE struct_fortran)
+add_test(NAME C_Fortran_struct COMMAND $<TARGET_FILE:c_fortran_struct>)
+
 # -- C++ calling Fortran
 add_executable(cxx_call_fortran cxx/main.cxx)
 target_link_libraries(cxx_call_fortran PRIVATE math_fortran)
@@ -38,6 +42,10 @@ add_test(NAME C++_Fortran_error
   COMMAND ${CMAKE_COMMAND} -Dexe=$<TARGET_FILE:cxx_fortran_error> -Dexp_code=42 -P ${PROJECT_SOURCE_DIR}/cmake/test_error.cmake
 )
 
+add_executable(cxx_fortran_struct cxx/struct_main.cxx)
+target_link_libraries(cxx_fortran_struct PRIVATE struct_fortran)
+add_test(NAME C++_Fortran_struct COMMAND $<TARGET_FILE:cxx_fortran_struct>)
+
 # -- test wrapup
 set_tests_properties(C++_Fortran_math C++_Fortran_error Fortran_call_C Fortran_call_C++ PROPERTIES
 TIMEOUT 5

src/c/struct_main.c

@@ -0,0 +1,27 @@
+#include <stdbool.h>
+#include <string.h>
+
+struct params {
+  // order and lengths must match in Fortran and C
+  int my_int;
+  bool my_bool;
+  int Lmy_char;
+  char my_char[1000];
+};
+
+extern void struct_check(struct params *);
+
+int main(void) {
+
+struct params s;
+
+s.my_int = 123;
+s.my_bool = true;
+strcpy(s.my_char, "Hello");
+s.Lmy_char = strlen(s.my_char);
+
+struct_check(&s);
+
+return 0;
+
+}

src/cxx/struct_main.cxx

@@ -0,0 +1,26 @@
+#include <cstring>
+
+struct params {
+  // order and lengths must match in Fortran and C
+  int my_int;
+  bool my_bool;
+  int Lmy_char;
+  char my_char[1000];
+};
+
+extern "C" void struct_check(struct params *);
+
+int main(void) {
+
+struct params s;
+
+s.my_int = 123;
+s.my_bool = true;
+strcpy(s.my_char, "Hello");
+s.Lmy_char = strlen(s.my_char);
+
+struct_check(&s);
+
+return 0;
+
+}

src/fortran/CMakeLists.txt

@@ -1,3 +1,5 @@
 add_library(math_fortran OBJECT math.f90)
 
 add_library(error_fortran OBJECT error.f90)
+
+add_library(struct_fortran OBJECT struct.f90)

src/fortran/meson.build

@@ -1,3 +1,5 @@
 math_fortran = library('math_fortran', 'math.f90')
 
 error_fortran = library('error_fortran', 'error.f90')
+
+struct_fortran = library('struct_fortran', 'struct.f90')

src/fortran/struct.f90

@@ -0,0 +1,50 @@
+module struct_rx
+
+use, intrinsic :: iso_c_binding, only : c_int, c_bool, c_char, c_null_char
+
+implicit none (type, external)
+
+
+type, bind(C) :: my_struct
+!! order and length must match in Fortran and C
+integer(c_int) :: my_int
+logical(c_bool) :: my_bool
+integer(c_int) :: Lmy_char
+character(kind=c_char) :: my_char(1000)
+!! character(kind=c_char) in bind(c) type cannot be allocatable. Just have to make it "long enough"
+!! or use iso_c_binding.h stuff
+
+end type my_struct
+
+
+contains
+
+
+pure subroutine struct_check(s) bind(C)
+
+type(my_struct), intent(in) :: s
+
+character(:), allocatable :: my_char
+
+if(s%my_int /= 123) error stop "my_int /= 123"
+if(.not. s%my_bool) error stop "my_bool /= .true."
+if(s%Lmy_char /= 5) error stop "Lmy_char /= 5"
+
+block
+  character(s%Lmy_char) :: buf
+  integer :: i
+  buf = "" !< ensure buf has no garbage characters
+
+  do i = 1, s%Lmy_char
+    if (s%my_char(i) == c_null_char) exit
+    buf(i:i) = s%my_char(i)
+  enddo
+  my_char = buf
+end block
+
+if(my_char /= "Hello") error stop "my_char /= 'Hello'"
+
+end subroutine struct_check
+
+
+end module struct_rx

src/meson.build

@@ -30,6 +30,15 @@ test('C Fortran error', c_fortran_error,
   timeout: 5,
   should_fail: true)
 
+c_fortran_struct = executable('c_fortran_struct',
+  sources: files('c/struct_main.c'),
+  link_with: struct_fortran,
+  link_language: 'fortran'
+)
+test('C Fortran struct', c_fortran_struct,
+  timeout: 5
+)
+
 # -- C++ calling Fortran
 cxx_call_fortran = executable('cxx_call_fortran',
   sources: files('cxx/main.cxx'),
@@ -45,3 +54,12 @@ cxx_fortran_error = executable('cxx_fortran_error',
 test('C++ Fortran error', cxx_fortran_error,
   timeout: 5,
   should_fail: true)
+
+cxx_fortran_struct = executable('cxx_fortran_struct',
+  sources: files('cxx/struct_main.cxx'),
+  link_with: struct_fortran,
+  link_language: 'fortran'
+)
+test('C++ Fortran struct', cxx_fortran_struct,
+  timeout: 5
+)