You can actually declare pointers to structure types you've never declared anywhere if you never dereference them, but when you do try and use their members, you get something like this...
I am using a structure defined as follows
struct gene_square
{
double *x;
double *y;
};I have class, with a member function which is a pointer of this type:
gene_square* m_Genes;I am allocating memory in the constructors like this:
m_Genes = new gene_square;
for (ii=0;... (1 Reply)
I'm getting the following Error:
prepare_pcap.c: In function `prepare_pkts':
prepare_pcap.c:127: error: dereferencing pointer to incomplete type
prepare_pcap.c:138: error: dereferencing pointer to incomplete type
====================================
This is the part of the relevant... (8 Replies)
// Hello all,
I am having this error "Dereferencing pointer to incomplete type " on these 2 lines:
xpoint = my_point->x;
ypoint = my_point->y;
I am having no clue y this is happening.
Any help would be greately appreciated!!!!
#include<stdio.h>
#include<string.h>... (2 Replies)
Suppose to have:
struct Tstudent
{
string name, surname;
int matriculation_num;
};
struct Tnode
{
Tstudent* student;
Tnodo* next;
} L;I want to deference that "student" pointer. For example, I tried with:
*(L->student).matriculation_numbut it not worked, as terminal... (4 Replies)
I am getting a dereferencing pointer to incomplete type error when i compile the following code on lines highlighted in red. Can anyone help me in identifying what is wrong in the code?
#include<stdio.h>
#include<stdlib.h>
typedef struct{
int info;
struct node* link ;
} node;
void... (3 Replies)
Hello.
I am new to this forum and I would like to ask for advice about low level POSIX programming.
I have to implement a POSIX compliant C shared library.
A file will have some variables and the shared library will have some functions which need those variables.
There is one special... (5 Replies)
Hi guys ,
i got segment fault , and when i trace , found it happens since the value of pointer which is returned by Struct S_client (*ptr) is zero
if (ptr !=0)i know , adding above line of code is not the solution and not correct for the case since above line only check for the pointer... (1 Reply)
I have a uint8_t *C = malloc(24*sizeof(uint8_t));
I need to send some integers and this *C to another node(in ad hoc network). So I am going to use a struct
` struct fulMsg {
int msgType;
int msgCount;
//uint8_t *CC;
} fulMsg_t;
typedef struct fulMsg fulMsg_tt;`
there is a method... (1 Reply)
Hi all!
I am trying to register a device in an existing device class, but I am
having trouble getting the pointer to an existing class.
I can create a class in a module, get the pointer to it and then use
it to register the device with:
*cl = class_create(THIS_MODULE, className);... (0 Replies)
Discussion started by: hdaniel@ualg.pt
0 Replies
LEARN ABOUT ULTRIX
shmctl
shmctl(2) System Calls Manual shmctl(2)Name
shmctl - shared memory control operations
Syntax
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
int shmctl (shmid, cmd, buf)
int shmid, cmd;
struct shmid_ds *buf;
Description
The system call provides a variety of shared memory control operations, as specified by cmd. The following cmds are available:
IPC_STAT Place the current value of each member of the data structure associated with shmid into the structure pointed to by buf.
The contents of this structure are defined in
IPC_SET Set the value of the following members of the data structure associated with shmid to the corresponding value found in the
structure pointed to by buf:
shm_perm.uid
shm_perm.gid
shm_perm.mode /* only low 9 bits */
This cmd can only be executed by a process that has an effective user ID equal to either that of the superuser or to the
value of in the data structure associated with shmid.
IPC_RMID Remove the shared memory identifier specified by shmid from the system and destroy the shared memory segment and data struc-
ture associated with it. This cmd can only be executed by a process that has an effective user ID equal to either that of
the superuser or to the value of in the data structure associated with shmid.
SHM_LOCK Lock the shared memory segment specified by shmid in memory. Lock prevents the shared memory segment from being swapped or
paged. This cmd can only be executed by a process that has an effective user ID equal to the superuser.
SHM_UNLOCK Unlock the shared memory segment specified by shmid. This cmd can only be executed by a process that has an effective user
ID equal to the superuser.
Return Values
Upon successful completion, a value of zero (0) is returned. Otherwise, a value of -1 is returned, and errno is set to indicated the
error.
Diagnostics
The system call fails if any of the following is true:
[EINVAL] The shmid is not a valid shared memory identifier.
[EINVAL] The cmd is not a valid command.
[EACCES] The cmd is equal to IPC_STAT, and read permission is denied to the calling process. For further information, see
[EPERM] The cmd is equal to IPC_RMID or IPC_SET, and the effective user ID of the calling process is not equal to that of the supe-
ruser or to the value of in the data structure associated with shmid.
[EPERM] The cmd is equal to SHM_LOCK or SHM_UNLOCK and the effective user ID of the calling process is not equal to that of the
superuser.
[EINVAL] The cmd is equal to SHM_LOCK, and the shared memory segment is currently locked by this process.
[EINVAL] The cmd is equal to SHM_UNLOCK, and the shared memory segment specified by shmid is not currently locked in memory by this
process.
[EFAULT] The buf points to an illegal address.
See Alsoshmget(2), shmop(2)shmctl(2)
02-05-2011
