Now you've turned it from invalid syntax, into something that's likely to crash... Think about what you're doing: You're trying to assign the contents of an unassigned pointer to NULL -- in other words, picking some random, arbitrary bit of memory and trying to write 0 into it.
Fortunately, this is a compiler error anyway since 0 isn't a ClassA.
How about:
NULL is like zero, but is of type void, which C++ won't complain about.
Hi
We are using a code generator for initializing structures with the #define macro. Compiling it with the GCC 2.8.1 (with -ansi) it OK. But when we are using the SUN C 5.0 compiler it screams.
Following is a code sample:
#include <stdlib.h>
#include <stdio.h>
typedef struct TEST3 {... (4 Replies)
If one wants to get a start address of a array or a string or a block of memory via a function, there are at least two methods to achieve it:
(1) one is to pass a pointer-to-pointer parameter, like:
int my_malloc(int size, char **pmem)
{
*pmem=(char *)malloc(size);
if(*pmem==NULL)... (11 Replies)
im just trying to have some fun and kill some time writing a c++ program that has a person type in a car make and model then gives them a year and a price. or something like that. i always have problems getting it goin but once the ball is rolling im usually pretty good. anyone wanna help me out? ... (1 Reply)
Hi, i have a question about C++. Is it possible to declare a class with a member ot the same class? For example, a linked list or i want to convert this C code to C++ class (Elemento)
typedef struct elemento
{
char name;
char value;
List<struct elemento> ltElementos;
... (7 Replies)
I'll be gratefull for any help. Thanks.
:)
This is the non class type error:
# g++ -I/usr/include/mysql -I/usr/include/mysql++ -lmysqlpp -L/usr/lib/mysql -L/usr/local/lib/mysql++ loaddsgsports.cpp -o loaddsgsports
loaddsgsports.cpp: In function âint outputToImport(const char*, const char*,... (1 Reply)
Hi,
I believe the next code is wrong:
class Egg {
Egg e;
int i;
Egg(int ii=0) : i(ii) {}
};
because you would end up with an endless definition (memory allocation) of Egg objects, thus int i.
Ok, so God Eckel proposes for a singleton:
class Egg {
static Egg e;
int... (5 Replies)
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)
I have the two class definition as follows.
class A { public: int a; };
class B : virtual public A{ };
The size of class A is shown as 4, and size of class B is shown as 16. Why is this effect ?. (2 Replies)
Hello All,
I am a learner in C++. I was testing my inheritance knowledge with following piece of code.
#include <iostream>
using namespace std;
class base
{
public :
void display()
{
cout << "In base display()" << endl;
}
void display(int k)
{... (2 Replies)
const int VALUES = {7,4,2,1,0}; //or int VALUES = {7,4,2,1,0};this statement inside a class definition gives error. Why? (3 Replies)
Discussion started by: milhan
3 Replies
LEARN ABOUT DEBIAN
kmem_free
kmem_alloc(9F) Kernel Functions for Drivers kmem_alloc(9F)NAME
kmem_alloc, kmem_zalloc, kmem_free - allocate kernel memory
SYNOPSIS
#include <sys/types.h>
#include <sys/kmem.h>
void *kmem_alloc(size_t size, int flag);
void *kmem_zalloc(size_t size, int flag);
void kmem_free(void*buf, size_t size);
INTERFACE LEVEL
Architecture independent level 1 (DDI/DKI).
PARAMETERS
size Number of bytes to allocate.
flag Determines whether caller can sleep for memory. Possible flags are KM_SLEEP to allow sleeping until memory is available,
or KM_NOSLEEP to return NULL immediately if memory is not available.
buf Pointer to allocated memory.
DESCRIPTION
kmem_alloc() allocates size bytes of kernel memory and returns a pointer to the allocated memory. The allocated memory is at least double-
word aligned, so it can hold any C data structure. No greater alignment can be assumed. flag determines whether the caller can sleep for
memory. KM_SLEEP allocations may sleep but are guaranteed to succeed. KM_NOSLEEP allocations are guaranteed not to sleep but may fail
(return NULL) if no memory is currently available. The initial contents of memory allocated using kmem_alloc() are random garbage.
kmem_zalloc() is like kmem_alloc() but returns zero-filled memory.
kmem_free() frees previously allocated kernel memory. The buffer address and size must exactly match the original allocation. Memory can-
not be returned piecemeal.
RETURN VALUES
If successful, kmem_alloc() and kmem_zalloc() return a pointer to the allocated memory. If KM_NOSLEEP is set and memory cannot be allo-
cated without sleeping, kmem_alloc() and kmem_zalloc() return NULL.
CONTEXT
kmem_alloc() and kmem_zalloc() can be called from interrupt context only if the KM_NOSLEEP flag is set. They can be called from user con-
text with any valid flag. kmem_free() can be called from user or interrupt context.
SEE ALSO copyout(9F), freerbuf(9F), getrbuf(9F)
Writing Device Drivers
WARNINGS
Memory allocated using kmem_alloc() is not paged. Available memory is therefore limited by the total physical memory on the system. It is
also limited by the available kernel virtual address space, which is often the more restrictive constraint on large-memory configurations.
Excessive use of kernel memory is likely to affect overall system performance. Overcommitment of kernel memory will cause the system to
hang or panic.
Misuse of the kernel memory allocator, such as writing past the end of a buffer, using a buffer after freeing it, freeing a buffer twice,
or freeing a null or invalid pointer, will corrupt the kernel heap and may cause the system to corrupt data or panic.
The initial contents of memory allocated using kmem_alloc() are random garbage. This random garbage may include secure kernel data. There-
fore, uninitialized kernel memory should be handled carefully. For example, never copyout(9F) a potentially uninitialized buffer.
NOTES
kmem_alloc(0, flag) always returns NULL. kmem_free(NULL, 0) is legal.
SunOS 5.10 24 Mar 2003 kmem_alloc(9F)