Hi,
when trying out uf a certain shared memory allocator would
work on Cygwin, I tried out the sample program below (which
works on Linunx, *BSD, AIX and Solaris) and got a suprising
falure with a segmentation fault at the line
*i1 = 42;
mmap() had succeeded.
Is this a known issue, and would it be possible to work
around that?
Best regards
Thomas
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#define NAME "/random_namexxx"
int main()
{
int fd;
long pagesize;
void *p1, *p2;
volatile int *i1, *i2;
size_t size1, size2;
off_t offset;
pagesize = sysconf (_SC_PAGE_SIZE);
if (pagesize == -1)
{
perror ("sysconf failed");
exit (EXIT_FAILURE);
}
fd = shm_open (NAME, O_CREAT | O_EXCL | O_RDWR, S_IRUSR | S_IWUSR);
if (fd == -1)
{
perror ("shm_open failed");
exit (EXIT_FAILURE);
}
shm_unlink (NAME);
offset = 0;
size1 = pagesize;
p1 = mmap (NULL, size1, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset);
if (p1 == MAP_FAILED)
{
perror ("mmap 1 failed");
exit (EXIT_FAILURE);
}
printf ("p1 = %p\n", p1);
ftruncate (fd, size1);
i1 = p1;
*i1 = 42;
size2 = 2 * size1;
p2 = mmap (NULL, size2, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset);
if (p2 == MAP_FAILED)
{
perror ("mmap 1 failed");
exit (EXIT_FAILURE);
}
printf ("p2 = %p\n", p2);
i2 = p2;
ftruncate (fd, size2);
printf ("%d\n", *i2);
return 0;
}
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