getline (C stdio.h) behaves incorrectly on 64 bit hardy/intrepid

I think the C function getline is behaving incorrectly in our 64 bit version of Ubuntu 8.04 and 8.10. The problem involves getline writing to areas of memory that it shouldn't. I agree that on the face of it that sounds unlikely. Here's my test code:

[CODE]
#include <stdlib.h>
#include <stdio.h>

int main(int argc, char **argv) {
    int i=10, maxlinelength=0 ;
    char *line=NULL ;

    maxlinelength = 0 ;
    line = NULL ;

    printf("%d, %d\n", i, maxlinelength) ;
    getline(&line, &maxlinelength, stdin) ;
    printf("%d, %d\n", i, maxlinelength) ;

    return 0 ;
}
[/CODE]

On 32 bit ubuntu 9.04 that prints what you'd expect:

[CODE]
10, 0

10, 120
[/CODE]

(the blank line comes from me hitting return when it tries to read from stdin; you can redirect a file into it if you want)

However on 64 bit ubuntu 8.04 and 8.10 that prints out

[CODE]
10, 0

0, 120
[/CODE]

I.e. it seems to me that getline has overwritten the memory location of the variable i.

The two machines that are producing incorrect results are

1)
[CODE]ash:~> lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 8.10
Release: 8.10
Codename: intrepid
ash:~> uname -a
Linux ash 2.6.27-11-server #1 SMP Thu Jan 29 20:13:12 UTC 2009 x86_64 GNU/Linux

[/CODE]
gcc 4.3.2

and

2)
[CODE]oak:~> uname -a
Linux oak 2.6.24-19-server #1 SMP Wed Aug 20 18:43:06 UTC 2008 x86_64 GNU/Linux
oak:~> lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 8.04.1
Release: 8.04
Codename: hardy
[/CODE]
gcc 4.2.4

Dan