IRC, freenode, #hurd, 2011-12-14

<pinotree> hm, interesting mmap bug
<youpi> ?
<pinotree> youpi:
#include <sys/types.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

void die(int x, const char *s)

static const char s_file[] = "foo-mmaptest";

int main()
  int fd;
  void *p;

  fd = creat(s_file, 0777);
  if (fd < 0) die(1, "creat");
  errno = 0;
  p = mmap(NULL, 1, PROT_READ, MAP_SHARED, fd, 0);
  printf("> %p vs %p, %d (%s)\n", p, MAP_FAILED, errno, strerror(errno));
  return (p != MAP_FAILED);
<pinotree> on linux it returns 0 and fails with EACCESS (as it seems it
  should, by reading the mmap posix docs), on hurd it returns 1 and the
  mmap succeeds
<pinotree> (taken from llvm's configure)
<youpi> why should it? file size extension ?
<pinotree> creat creates a o_wronly file, while the mmap specifies only
  read protection
<youpi> oh, craet is always wo
<youpi> I didn't know that