hi,
I have made a small C program that make use of malloc and free for processing bitmap images. when i try to run the program, I am getting a error something like
*** glibc detected *** free(): invalid next size (normal): 0x0000000000503e70 ***
I am not sure of which free() is causing this... (1 Reply)
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)
there seems not to be error in this segment. In some computers, it can work well. But in others, it will give a failure.
why it ocurrs and how to deal with it?
in a function:
if( *ver == NULL ) {
*ver = (vertex *) malloc(sizeof(vertex)); //this line
... (17 Replies)
Hi,
I am having a hell of a time getting this to work. So basically, I have opened a popen to run a program that is going to prompt an action to occur half way through, when it gets to this I need to create a separate process and do some stuff, then return to the original process. This works... (0 Replies)
*** glibc detected *** ./a.out: malloc(): memory corruption (fast):
Posted A minute ago
M trying to make multiway tree and dont know what happend when this part of code get executed:
01void ins(NODE *ptr)
02{
03 //working
04 if(ptr!=NULL)
05 {
06 SNODE *var=NULL;
07 var=(SNODE... (3 Replies)
Hello.
I'm looking for a quite "interesting" bug I'm using fortran 90, compiler gfortran and the main idea is for every time step I build a bin structure for search contact between particles, for this at the begining
TYPE :: circle_index
INTEGER(kind = 4) :: ind_p
TYPE(circle_index),... (1 Reply)
I am facing a problem of memory corruption. The loop runs for the first time but does not go through the second time. What could be the problem?
for(int z=0;z<2;z++)
{
fp=fopen("poly.dat","r");
/*do something which reads this file into a 2D array*/
fclose(fp);
... (10 Replies)
Currently I test a shared library vendor provided in linux , the following is the simple source :
#include <iostream>
using namespace std;
extern int test1();
extern int test2();
int main()
{
cout << "hello world" << endl ;
return 0 ;
cout << "Test 1" << endl;
... (6 Replies)
Use and complete the template provided. The entire template must be completed. If you don't, your post may be deleted!
1. The problem statement, all variables and given/known data:
I'm doing aproximation of derivative called five-point stencil. For every value of x, in interval , in step... (0 Replies)
Discussion started by: antonija
0 Replies
LEARN ABOUT SUSE
calloc
MALLOC(3) Linux Programmer's Manual MALLOC(3)NAME
calloc, malloc, free, realloc - Allocate and free dynamic memory
SYNOPSIS
#include <stdlib.h>
void *calloc(size_t nmemb, size_t size);
void *malloc(size_t size);
void free(void *ptr);
void *realloc(void *ptr, size_t size);
DESCRIPTION
calloc() allocates memory for an array of nmemb elements of size bytes each and returns a pointer to the allocated memory. The memory is
set to zero. If nmemb or size is 0, then calloc() returns either NULL, or a unique pointer value that can later be successfully passed to
free().
malloc() allocates size bytes and returns a pointer to the allocated memory. The memory is not cleared. If size is 0, then malloc()
returns either NULL, or a unique pointer value that can later be successfully passed to free().
free() frees the memory space pointed to by ptr, which must have been returned by a previous call to malloc(), calloc() or realloc(). Oth-
erwise, or if free(ptr) has already been called before, undefined behavior occurs. If ptr is NULL, no operation is performed.
realloc() changes the size of the memory block pointed to by ptr to size bytes. The contents will be unchanged to the minimum of the old
and new sizes; newly allocated memory will be uninitialized. If ptr is NULL, then the call is equivalent to malloc(size), for all values
of size; if size is equal to zero, and ptr is not NULL, then the call is equivalent to free(ptr). Unless ptr is NULL, it must have been
returned by an earlier call to malloc(), calloc() or realloc(). If the area pointed to was moved, a free(ptr) is done.
RETURN VALUE
For calloc() and malloc(), return a pointer to the allocated memory, which is suitably aligned for any kind of variable. On error, these
functions return NULL. NULL may also be returned by a successful call to malloc() with a size of zero, or by a successful call to calloc()
with nmemb or size equal to zero.
free() returns no value.
realloc() returns a pointer to the newly allocated memory, which is suitably aligned for any kind of variable and may be different from
ptr, or NULL if the request fails. If size was equal to 0, either NULL or a pointer suitable to be passed to free() is returned. If real-
loc() fails the original block is left untouched; it is not freed or moved.
CONFORMING TO
C89, C99.
NOTES
Normally, malloc() allocates memory from the heap, and adjusts the size of the heap as required, using sbrk(2). When allocating blocks of
memory larger than MMAP_THRESHOLD bytes, the glibc malloc() implementation allocates the memory as a private anonymous mapping using
mmap(2). MMAP_THRESHOLD is 128 kB by default, but is adjustable using mallopt(3). Allocations performed using mmap(2) are unaffected by
the RLIMIT_DATA resource limit (see getrlimit(2)).
The Unix98 standard requires malloc(), calloc(), and realloc() to set errno to ENOMEM upon failure. Glibc assumes that this is done (and
the glibc versions of these routines do this); if you use a private malloc implementation that does not set errno, then certain library
routines may fail without having a reason in errno.
Crashes in malloc(), calloc(), realloc(), or free() are almost always related to heap corruption, such as overflowing an allocated chunk or
freeing the same pointer twice.
Recent versions of Linux libc (later than 5.4.23) and glibc (2.x) include a malloc() implementation which is tunable via environment vari-
ables. When MALLOC_CHECK_ is set, a special (less efficient) implementation is used which is designed to be tolerant against simple
errors, such as double calls of free() with the same argument, or overruns of a single byte (off-by-one bugs). Not all such errors can be
protected against, however, and memory leaks can result. If MALLOC_CHECK_ is set to 0, any detected heap corruption is silently ignored;
if set to 1, a diagnostic message is printed on stderr; if set to 2, abort(3) is called immediately; if set to 3, a diagnostic message is
printed on stderr and the program is aborted. Using a nonzero MALLOC_CHECK_ value can be useful because otherwise a crash may happen much
later, and the true cause for the problem is then very hard to track down.
BUGS
By default, Linux follows an optimistic memory allocation strategy. This means that when malloc() returns non-NULL there is no guarantee
that the memory really is available. This is a really bad bug. In case it turns out that the system is out of memory, one or more pro-
cesses will be killed by the infamous OOM killer. In case Linux is employed under circumstances where it would be less desirable to sud-
denly lose some randomly picked processes, and moreover the kernel version is sufficiently recent, one can switch off this overcommitting
behavior using a command like:
# echo 2 > /proc/sys/vm/overcommit_memory
See also the kernel Documentation directory, files vm/overcommit-accounting and sysctl/vm.txt.
SEE ALSO brk(2), mmap(2), alloca(3), posix_memalign(3)COLOPHON
This page is part of release 3.25 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
GNU 2009-01-13 MALLOC(3)