[Gc] Interior pointers

[Michael Talbot-Wilson]

Guys, thanks.  Here is the full program.  (Assuming I can send an
attachment to this mailing list.)

Hope you can put me straight.

--Mike
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/* Copied from the getdents(2) manpage and modified. */
/*
 *      $(CC) -o $(PROGNAME) \
 *      -I./gc-7.2d/include $(PROGNAME).c ./gc-7.2d/.libs/libgc.a
 */

#define _GNU_SOURCE
#include <dirent.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#define GC_DEBUG
#include <gc.h>

#define handle_error(msg) \
  do { perror(msg);exit(EXIT_FAILURE); } while (0)

struct linux_dirent {
  long d_ino;
  off_t d_off;
  unsigned short d_reclen;
  char d_name[];
};

int off_to_name = sizeof(long) + sizeof(off_t) + sizeof(short);

#define BUF_SIZE 1024

int main(int argc, char *argv[])
{
  int fd, nread, bpos, k;
  /*  char buf[BUF_SIZE]; */
  char *buf;
  struct linux_dirent *d;

  GC_INIT();

  /* array holding pointers to 5000 names */
  char **allnames = (char **) GC_MALLOC(5000);
  int array_subscript=0;

  fd = open(argc>1 ? argv[1] : ".", O_RDONLY | O_DIRECTORY);

  if (fd==-1)
    handle_error("open");

  for (;;) {

    buf = (char *) GC_MALLOC(BUF_SIZE);

    nread = syscall(SYS_getdents, fd, buf, BUF_SIZE);

    if (nread==-1)
      handle_error("getdents");

    if (nread==0)
      break;

    for (bpos=0; bpos<nread;) {
      d = (struct linux_dirent *) (buf+bpos);

      allnames[array_subscript++] = (char *)d + off_to_name;

      printf("& allnames[0]=%ld\n", (long) &(allnames[0]));
      printf("1 allnames[0]=%s\n", allnames[0]);
      printf("2 allnames[%d]=%s\n",
	     array_subscript-1, allnames[array_subscript-1]);

      bpos+=d->d_reclen;
    }
  }
  close(fd);
  exit(EXIT_SUCCESS);
}