MCHECK(3) | Linux Programmer's Manual | MCHECK(3) |
NAME
mcheck, mcheck_check_all, mcheck_pedantic, mprobe - heap consistency checkingSYNOPSIS
#include<mcheck.h>
int mcheck(void (* abortfunc )(enum mcheck_status mstatus ));
int mcheck_pedantic(void (*abortfunc)(enum mcheck_status mstatus));
void
mcheck_check_all(void);
enum mcheck_status mprobe(void *ptr);
DESCRIPTION
The mcheck() function installs a set of debugging hooks for the malloc(3) family of memory-allocation functions. These hooks cause certain consistency checks to be performed on the state of the heap. The checks can detect application errors such as freeing a block of memory more than once or corrupting the bookkeeping data structures that immediately precede a block of allocated memory.- MCHECK_DISABLED ( mprobe() only)
- mcheck() was not called before the first memory allocation function was called. Consistency checking is not possible.
- MCHECK_OK ( mprobe() only)
- No inconsistency detected.
- MCHECK_HEAD
- Memory preceding an allocated block was clobbered.
- MCHECK_TAIL
- Memory following an allocated block was clobbered.
- MCHECK_FREE
- A block of memory was freed twice.
RETURN VALUE
mcheck() and mcheck_pedantic() return 0 on success, or -1 on error.VERSIONS
The mcheck_pedantic() and mcheck_check_all() functions are available since glibc 2.2. The mcheck() and mprobe() functions are present since at least glibc 2.0CONFORMING TO
These functions are GNU extensions.NOTES
Linking a program with -lmcheck and using the MALLOC_CHECK_ environment variable (described in mallopt(3)) cause the same kinds of errors to be detected. But, using MALLOC_CHECK_ does not require the application to be relinked.EXAMPLE
The program below calls mcheck() with a NULL argument and then frees the same block of memory twice. The following shell session demonstrates what happens when running the program:
$ ./a.out
About to free
About to free a second time
block freed twice
Aborted (core dumped)
Program source
#include <stdlib.h>
#include <stdio.h>
#include <mcheck.h>
int
main(int argc, char *argv[])
{
char *p;
if (mcheck(NULL) != 0) {
fprintf(stderr, "mcheck() failed\n");
exit(EXIT_FAILURE);
}
p = malloc(1000);
fprintf(stderr, "About to free\n");
free(p);
fprintf(stderr, "\nAbout to free a second time\n");
free(p);
exit(EXIT_SUCCESS);
}
SEE ALSO
malloc(3), mallopt(3), mtrace(3)COLOPHON
This page is part of release 3.53 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/.2012-04-18 | GNU |