Can Any body give me a exampla which has the usage of realloc
i want a function which uses realloc & increases /decreases the size of a pointer (0 Replies)
Hello,
my program works properly but valgrind tells me I am not freeing allocated memory. I think the problem is in realloc.
I am pretty sure I do something wrong with realloc, because I changed it a bit and valgrind noticed less errors (that the program wasn't working properly with less errors... (3 Replies)
hi,
I'm using gcc version 3.4.6 on a Red Hat system... (not sure how to determine version of glibc)
when i run the following, i get:
glibc detected *** realloc(): invalid next size: 0x0804a170
I'm not sure what is wrong. The error happens on the second iteration of
the while loop.... (3 Replies)
N00B here. This function would be easier using a char pointer along with free. But I wish to learn how to use char static pointers (they do not require free, right ?).
How do I erase the content of a static pointer ? Terminating the string works but the static pointer's content is not being... (4 Replies)
Hi,
I am seeing varying results about, when realloc() fails in reallocation.
Which one is correct out of the below?
a) realloc() maintains the original pointer (i.e) the original pointer is left unaltered/untouched but relloc() returns the NULL value.
b) original buffer pointer is lost... (3 Replies)
Hi all
I'm trying to use someone else's software, which has a realloc that fails in it. This is probably due to memory limitations, as it only happens when I use this software on huge datasets.
First question : how to diagnose if it's a soft or hard limitation? I mean, if it's due to my... (10 Replies)
b = realloc(a, 1000);
if realloc succeeds and b!=a (not in-place replacement), does realloc automatically free a or I should free both a and b afterwards?
thank you! (5 Replies)
Not sure in which forum to post this. I'm trying here, in Programming.
I'm working on a PC with Intel Duo processor & 2GB of ram. OS is Ubuntu 10.04.
I'm having problems with a C++ program that makes extensive use of realloc(). It happens that as soon as the overall memory allocated(OS +... (14 Replies)
Hi everyone,
i made this program. is a simple one for practising malloc, realloc and structs.
I have a struct named shop as global variable in which i take the size of the matrix from the keyboard and after i malloc it.
I insert the values with the fullarray() and after i print the matrix with... (7 Replies)
Discussion started by: giampoul
7 Replies
LEARN ABOUT NETBSD
malloc
MALLOC(3) BSD Library Functions Manual MALLOC(3)NAME
malloc, calloc, realloc, free -- general purpose memory allocation functions
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <stdlib.h>
void *
malloc(size_t size);
void *
calloc(size_t number, size_t size);
void *
realloc(void *ptr, size_t size);
void
free(void *ptr);
DESCRIPTION
The malloc() function allocates size bytes of uninitialized memory. The allocated space is suitably aligned (after possible pointer coer-
cion) for storage of any type of object.
The calloc() function allocates space for number objects, each size bytes in length. The result is identical to calling malloc() with an
argument of ``number * size'', with the exception that the allocated memory is explicitly initialized to zero bytes.
The realloc() function changes the size of the previously allocated memory referenced by ptr to size bytes. The contents of the memory are
unchanged up to the lesser of the new and old sizes. If the new size is larger, the value of the newly allocated portion of the memory is
undefined. Upon success, the memory referenced by ptr is freed and a pointer to the newly allocated memory is returned. Note that realloc()
may move the memory allocation, resulting in a different return value than ptr. If ptr is NULL, the realloc() function behaves identically
to malloc() for the specified size.
The free() function causes the allocated memory referenced by ptr to be made available for future allocations. If ptr is NULL, no action
occurs.
RETURN VALUES
The malloc() and calloc() functions return a pointer to the allocated memory if successful; otherwise a NULL pointer is returned and errno is
set to ENOMEM.
The realloc() function returns a pointer, possibly identical to ptr, to the allocated memory if successful; otherwise a NULL pointer is
returned, and errno is set to ENOMEM if the error was the result of an allocation failure. The realloc() function always leaves the original
buffer intact when an error occurs.
The free() function returns no value.
EXAMPLES
When using malloc(), be careful to avoid the following idiom:
if ((p = malloc(number * size)) == NULL)
err(EXIT_FAILURE, "malloc");
The multiplication may lead to an integer overflow. To avoid this, calloc() is recommended.
If malloc() must be used, be sure to test for overflow:
if (size && number > SIZE_MAX / size) {
errno = EOVERFLOW;
err(EXIT_FAILURE, "allocation");
}
When using realloc(), one must be careful to avoid the following idiom:
nsize += 50;
if ((p = realloc(p, nsize)) == NULL)
return NULL;
Do not adjust the variable describing how much memory has been allocated until it is known that the allocation has been successful. This can
cause aberrant program behavior if the incorrect size value is used. In most cases, the above example will also leak memory. As stated ear-
lier, a return value of NULL indicates that the old object still remains allocated. Better code looks like this:
newsize = size + 50;
if ((p2 = realloc(p, newsize)) == NULL) {
if (p != NULL)
free(p);
p = NULL;
return NULL;
}
p = p2;
size = newsize;
SEE ALSO madvise(2), mmap(2), sbrk(2), alloca(3), atexit(3), getpagesize(3), memory(3), posix_memalign(3)
For the implementation details, see jemalloc(3).
STANDARDS
The malloc(), calloc(), realloc() and free() functions conform to ISO/IEC 9899:1990 (``ISO C90'').
BSD May 3, 2010 BSD