Fortran 2003 C-interoperable code: possible wrong assembly generation by the compiler
Hi,
I'm exploring the opportunities offered by the Fortran 2003 standard to create C-interoperable functions and subroutines and I stumbled in what seems like an error in the code generated by the compiler on a rather simple function.
Here is the fortran module (lines marked as OPTIONAL can be commented without changing the behaviour of the code generated, I left them to give an idea of what my original test was):
----------- test_module.f90 -----------
module test_module
contains
function arrayfunc(size) bind(c)
use iso_c_binding
implicit none
integer(c_int),value::size
type(c_ptr),target::arrayfunc
real(c_double),target,allocatable,dimension(:)::array
integer::i !OPTIONAL
print *,"The size received is: ",size
allocate(array(1:size)) ! OPTIONAL
if (.not. allocated(array)) then ! OPTIONAL
print *, "Array not allocated..." ! OPTIONAL
end if ! OPTIONAL
! OPTIONAL
do i=1,size ! OPTIONAL
array(i) = i*i ! OPTIONAL
enddo ! OPTIONAL
! OPTIONAL
arrayfunc=C_LOC(array) ! OPTIONAL
return
end function arrayfunc
end module test_module
----------------------------
Here is the C header file:
----------- test_module.h -----------
#ifndef TEST__MODULE_H
#define TEST__MODULE_H
// Intent: interface Fortran with C to create a function that returns
// a C array of allocated memory
extern double *arrayfunc(int size);
#endif
----------------------------------------
And this is the C code used to call the fortran function:
------------- test.c -----------------
#include <stdlib.h>
#include <stdio.h>
#include "test_module.h"
int main(int argc, char *argv[])
{
double *testarray=NULL;
int i;
testarray=arrayfunc(10);
for(i=0;i<10;i++)
printf("Element %2d of the Fortran array: %gn", i, testarray[i]);
return 0;
}
---------------------------
The function arrayfunc (which should have allocated an array and passed it to the C function) is supposed to print it's "size" argument as the first action (10, which is to be received by value, as explicitly specified in the declaration), however both on ifort 10.1 (ia32) and ifort Version 11.1 (ia64) where I tested the code, the argument seems to be received incorrectly (in fact in the 64bit example, the variable seems to point to uninitialized memory...).
This is what happens with ifort 10.1 on my atom N270 (ia32):
$ ./test
The size received is: 134520820
and those are a couple of results on my Q9550 (ia64 with a 64bit ubuntu):
$ ./test
The size received is: -1720334552
Segmentation fault
$ ./test
The size received is: -2028769016
Segmentation fault
$ ./test
The size received is: 1024856360
forrtl: severe (41): insufficient virtual memory
Image PC Routine Line Source
libintlc.so.5 00007F6133E3BB2D Unknown Unknown Unknown
libintlc.so.5 00007F6133E3A635 Unknown Unknown Unknown
libifcore.so.5 00007F6134842535 Unknown Unknown Unknown
libifcore.so.5 00007F61347B4A2D Unknown Unknown Unknown
libifcore.so.5 00007F6134801CF8 Unknown Unknown Unknown
libifcore.so.5 00007F6134801B51 Unknown Unknown Unknown
libtest_module.so 00007F6134D4198B Unknown Unknown Unknown
test 000000000040068D Unknown Unknown Unknown
libc.so.6 00007F61349ED5A6 Unknown Unknown Unknown
test 00000000004005A9 Unknown Unknown Unknown
I have tested the same example with 2 other compilers on both computers and the result was, as expected, something like:
The size received is: 10
Element 0 of the Fortran array: 1
Element 1 of the Fortran array: 4
Element 2 of the Fortran array: 9
Element 3 of the Fortran array: 16
Element 4 of the Fortran array: 25
Element 5 of the Fortran array: 36
Element 6 of the Fortran array: 49
Element 7 of the Fortran array: 64
Element 8 of the Fortran array: 81
Element 9 of the Fortran array: 100
The code was interfaced with gcc-4.33 (although for what I know about assembly I'm rather positive it isn't relevant to the matter at hand) and the fortran code compiled in many different ways (as a shared library, as a simple object file, with/without debugging symbols, with/without optimization enabled and so forth...).
Now because I'm not coding in Fortran since a long while the fortran code might not be fit to my purpose, however I think there is still a glitch in the compiler that might be worth a bug report.
I read some documentation on this site and elsewhere about C-Fortran interfaces, but since I'm new to the task, any comment, suggestion or costructive critic will be highly appreciated.
Thank you for your time and patience,
Riccardo
PS: I apologize for the poor look of this post (I'm in the software network since half an hour and I'm not yet skilled with the composer :-) )
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