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Memcheck: a memory error detector

•

check_memory [addressable|defined] <addr> [<len>]

checks that the range of <len> (default 1)

bytes at <addr> has the specified accessibility. It then outputs a description of <addr>. In the following example, a
detailed description is available because the option

--read-var-info=yes

was given at Valgrind startup:

(gdb) monitor check_memory defined 0x8049e28

Address 0x8049E28 len 1 defined

==14698==

Location 0x8049e28 is 0 bytes inside string10[0],

==14698==

declared at prog.c:10, in frame #0 of thread 1

(gdb)

•

performs a leak check. The

in the argu-

ments indicates the default values.

If the first argument is

summary

, only a summary of the leak search is given; otherwise a full leak report is

produced.

A full leak report gives detailed information for each leak: the stack trace where the leaked blocks

were allocated, the number of blocks leaked and their total size.

When a full report is requested, the next two

arguments further specify what kind of leaks to report. A leak’s details are shown if they match both the second
and third argument. A full leak report might output detailed information for many leaks. The nr of leaks for which
information is output can be controlled using the

limited

argument followed by the maximum nr of leak records

to output. If this maximum is reached, the leak search outputs the records with the biggest number of bytes.

The second argument controls what kind of blocks are shown for a

full

leak search. The value

definiteleak

specifies that only definitely leaked blocks should be shown. The value

possibleleak

will also show possibly

leaked blocks (those for which only an interior pointer was found).

The value

reachable

will show all block

categories (reachable, possibly leaked, definitely leaked).

The third argument controls what kinds of changes are shown for a

full

leak search. The value

increased

specifies that only block allocation stacks with an increased number of leaked bytes or blocks since the previous
leak check should be shown.

The value

changed

specifies that allocation stacks with any change since the

previous leak check should be shown. The value

any

specifies that all leak entries should be shown, regardless of

any increase or decrease. When If

increased

changed

are specified, the leak report entries will show the

delta relative to the previous leak report.

The following example shows usage of the

leak_check

monitor command on the

memcheck/tests/leak-cases.c

regression test. The first command outputs one entry having an increase in the leaked bytes. The second command
is the same as the first command, but uses the abbreviated forms accepted by GDB and the Valgrind gdbserver. It
only outputs the summary information, as there was no increase since the previous leak search.

(gdb) monitor leak_check full possibleleak increased

==19520== 16 (+16) bytes in 1 (+1) blocks are possibly lost in loss record 9 of 12

==19520==

at 0x40070B4: malloc (vg_replace_malloc.c:263)

==19520==

by 0x80484D5: mk (leak-cases.c:52)

==19520==

by 0x804855F: f (leak-cases.c:81)

==19520==

by 0x80488E0: main (leak-cases.c:107)

==19520==

==19520== LEAK SUMMARY: