Concerning a post that you made about expandable anonymous sharedmappings

[William Tambe]

I read a post that you made about not being able to expand anonymous 
shared mapping with mremap(). And I am actually having that issue now.

You made the post in 2004 and we are now in 2007. I would like to know 
if that feature was added because the code below always fail with bus 
error on my machine. I use glibc 2.5

Thank you for helping.

#define _GNU_SOURCE
#include <sys/mman.h>
#include <unistd.h>

#include <stdio.h>

main() {
        void *ptr;
        if ((ptr=mmap(0, 4096, PROT_READ|PROT_WRITE,
                MAP_ANONYMOUS|MAP_SHARED|MAP_GROWSDOWN, 0, 0)) == -1) {
                printf("failed to mmap\n");
                return;
        }

        if ((ptr=mremap(ptr, 4096, 8192, MREMAP_MAYMOVE)) == -1) {
                printf("failed to mremap\n");
                return;
        }

        //why does this failed. I am well in the interval [4096, 8192]
        *(unsigned int *)(ptr + 4096 + 8)= 10;
}
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