трассировка malloc (malloc tracing)
Имя (Name)
mtrace, muntrace - malloc tracing
Синопсис (Synopsis)
#include <mcheck.h>
void mtrace(void);
void muntrace(void);
Описание (Description)
The mtrace() function installs hook functions for the memory-
allocation functions (malloc(3), realloc(3) memalign(3),
free(3)). These hook functions record tracing information about
memory allocation and deallocation. The tracing information can
be used to discover memory leaks and attempts to free
nonallocated memory in a program.
The muntrace() function disables the hook functions installed by
mtrace(), so that tracing information is no longer recorded for
the memory-allocation functions. If no hook functions were
successfully installed by mtrace(), muntrace() does nothing.
When mtrace() is called, it checks the value of the environment
variable MALLOC_TRACE, which should contain the pathname of a
file in which the tracing information is to be recorded. If the
pathname is successfully opened, it is truncated to zero length.
If MALLOC_TRACE is not set, or the pathname it specifies is
invalid or not writable, then no hook functions are installed,
and mtrace() has no effect. In set-user-ID and set-group-ID
programs, MALLOC_TRACE is ignored, and mtrace() has no effect.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌────────────────────────────────────┬───────────────┬───────────┐
│Interface │ Attribute │ Value │
├────────────────────────────────────┼───────────────┼───────────┤
│mtrace(), muntrace() │ Thread safety │ MT-Unsafe │
└────────────────────────────────────┴───────────────┴───────────┘
Стандарты (Conforming to)
These functions are GNU extensions.
Примечание (Note)
In normal usage, mtrace() is called once at the start of
execution of a program, and muntrace() is never called.
The tracing output produced after a call to mtrace() is textual,
but not designed to be human readable. The GNU C library
provides a Perl script, mtrace(1), that interprets the trace log
and produces human-readable output. For best results, the traced
program should be compiled with debugging enabled, so that line-
number information is recorded in the executable.
The tracing performed by mtrace() incurs a performance penalty
(if MALLOC_TRACE points to a valid, writable pathname).
Ошибки (баги) (Bugs)
The line-number information produced by mtrace(1) is not always
precise: the line number references may refer to the previous or
following (nonblank) line of the source code.
Примеры (Examples)
The shell session below demonstrates the use of the mtrace()
function and the mtrace(1) command in a program that has memory
leaks at two different locations. The demonstration uses the
following program:
$ cat t_mtrace.c
#include <mcheck.h>
#include <stdlib.h>
#include <stdio.h>
int
main(int argc, char *argv[])
{
mtrace();
for (int j = 0; j < 2; j++)
malloc(100); /* Never freed--a memory leak */
calloc(16, 16); /* Never freed--a memory leak */
exit(EXIT_SUCCESS);
}
When we run the program as follows, we see that mtrace()
diagnosed memory leaks at two different locations in the program:
$ cc -g t_mtrace.c -o t_mtrace
$ export MALLOC_TRACE=/tmp/t
$ ./t_mtrace
$ mtrace ./t_mtrace $MALLOC_TRACE
Memory not freed:
-----------------
Address Size Caller
0x084c9378 0x64 at /home/cecilia/t_mtrace.c:12
0x084c93e0 0x64 at /home/cecilia/t_mtrace.c:12
0x084c9448 0x100 at /home/cecilia/t_mtrace.c:16
The first two messages about unfreed memory correspond to the two
malloc(3) calls inside the for loop. The final message
corresponds to the call to calloc(3) (which in turn calls
malloc(3)).
Смотри также (See also)
mtrace(1), malloc(3), malloc_hook(3), mcheck(3)
