Problem with linked lists Post: 302277010

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Top Forums Programming Problem with linked lists Post 302277010 by spirtle on Thursday 15th of January 2009 06:07:25 AM

01-15-2009

Registered User

This line is dodgy:

Code:

data[0].friends=malloc(2*sizeof(struct record));

record::friends is of type pointer to pointer to struct record, but you are allocating space for two structs, which isn't the same thing. You need friends to point to the memory you allocated.
Try this

Code:

#include <stdio.h>
#include <stdlib.h>

struct record {
  int id;
  struct record **friends;
};

void subroutine(struct record **data){
    int i;
    *data=malloc(3*sizeof **data);
    struct record* friends = malloc(2*sizeof *friends);
    (*data)[0].friends=&friends;
    for(i=0;i<3;i++) (*data)[i].id=i;
    (*data)[0].friends[0]=data[1];
    printf("%d %d\n", (*data)[0].id, (*data)[0].friends[0]->id);
}

int main(){
    int i;
    struct record *data;

/* This uncommented piece of code works as it is supposed to */
  data=malloc(3*sizeof *data);
  struct record* friends = malloc(2*sizeof *friends);
  data[0].friends=&friends;
  for(i=0;i<3;i++) data[i].id=i;
  data[0].friends[0]=&data[1];
  printf("%d %d\n", data[0].id, data[0].friends[0]->id);

  struct record *data1;
  subroutine(&data1);
  return EXIT_SUCCESS;
}

spirtle

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LEARN ABOUT DEBIAN

pts_chown

PTS_CHOWN(1)						       AFS Command Reference						      PTS_CHOWN(1)

NAME

       pts_chown - Changes the owner of a Protection Database entry

SYNOPSIS

       pts chown -name <group name> -owner <new owner>
	   [-cell <cell name>] [-noauth] [-localauth] [-force] [-help]

       pts cho -na <group name> -o <new owner>
	   [-c <cell name>] [-no] [-l] [-f] [-h]

DESCRIPTION

       The pts chown command designates the user or group named by the -owner argument as the owner of the group named by the -name argument, and
       records the new owner in the owner field of the group's Protection Database entry.

       In the case of regular groups, this command automatically changes the group name's owner prefix (the part of the group name before the
       colon) to match the new owner. If the new owner is itself a group, then only its owner prefix, not its complete name, becomes the owner
       prefix in the new name. The change to the owner prefix does not propagate to any groups owned by the group, however. To make the owner
       prefix of such group-owned groups reflect the new owning group, use the pts rename command.

       It is not possible to change a user or machine entry's owner from the default set at creation time, the system:administrators group.

CAUTIONS

       While designating a machine as a group's owner does not cause an error, it is not recommended. The Protection Server does not extend the
       usual privileges of group ownership to users logged onto the machine.

OPTIONS

       -name <group name>
	   Specifies the current name of the group to which to assign a new owner.

       -owner <new owner>
	   Names the user or group to become the group's owner.

       -cell <cell name>
	   Names the cell in which to run the command. For more details, see pts(1).

       -force
	   Enables the command to continue executing as far as possible when errors or other problems occur, rather than halting execution at the
	   first error.

       -help
	   Prints the online help for this command. All other valid options are ignored.

       -localauth
	   Constructs a server ticket using a key from the local /etc/openafs/server/KeyFile file. Do not combine this flag with the -cell or
	   -noauth options. For more details, see pts(1).

       -noauth
	   Assigns the unprivileged identity anonymous to the issuer. For more details, see pts(1).

EXAMPLES

       The following example changes the owner of the group "terry:friends" from the user "terry" to the user "pat". A side effect is that the
       group name changes to "pat:friends".

	  % pts chown -name terry:friends -owner pat

       The following example changes the owner of the group "terry:friends" from the user "terry" to the group "pat:buddies". A side effect is
       that the group name changes to "pat:friends".

	  % pts chown -name terry:friends -owner pat:buddies

PRIVILEGE REQUIRED

       The issuer must belong to the system:administrators group or currently own the group.

SEE ALSO

       pts(1), pts_rename(1)

COPYRIGHT

       IBM Corporation 2000. <http://www.ibm.com/> All Rights Reserved.

       This documentation is covered by the IBM Public License Version 1.0.  It was converted from HTML to POD by software written by Chas
       Williams and Russ Allbery, based on work by Alf Wachsmann and Elizabeth Cassell.

OpenAFS 							    2014-04-08							      PTS_CHOWN(1)