Memory Allocation Library Functions umemdebug(3MALOC)
NAME
umemdebug - debugging features of the umem library
SYNOPSIS
cc [ flag... ] file... -lumem [ library... ]
#include
DESCRIPTION
The libumem library provides debugging features that detect
memory leaks, buffer overruns, multiple frees, use of unini-
tialized data, use of freed data, and many other common pro-
gramming errors. The activation of the run-time debugging
features is controlled by environment variables.
When the library detects an error, it writes a description
of the error to an internal buffer that is readable with the
::umemstatus mdb(1) dcmd and then calls abort(3C).
ENVIRONMENT VARIABLES
UMEMDEBUG This variable contains a list of comma-
separated options. Unrecognized options are
ignored. Possible options include:
audit[=frames] This option enables the
recording of auditing
information, including
thread ID, high-
resolution time stamp,
and stack trace for the
last action (allocation
or free) on every allo-
cation. If transaction
logging (see
UMEMLOGING) is
enabled, this auditing
information is also
logged.
The frames parameter
sets the number of stack
frames recorded in the
auditing structure. The
upper bound for frames
is implementation-
defined. If a larger
value is requested, the
upper bound is used
instead.
If frames is not
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Memory Allocation Library Functions umemdebug(3MALOC)
specified or is not an
integer, the default
value of 15 is used.
This option also enables
the guards option.
contents[=count] If auditing and contents
logging (see
UMEMLOGING) are
enabled, the first count
bytes of each buffer are
logged when they are
freed. If a buffer is
shorter than count
bytes, it is logged in
its entirety.
If count is not speci-
fied or is not an
integer, the default
value of 256 is used.
default This option is
equivalent to
audit,contents,guards.
guards This option enables fil-
ling allocated and freed
buffers with special
patterns to help detect
the use of uninitialized
data and previously
freed buffers. It also
enables an 8-byte red-
zone after each buffer
that contains
0xfeedfacefeedfaceUL.
When an object is freed,
it is filled with
0xdeadbeef. When an
object is allocated, the
0xdeadbeef pattern is
verified and replaced
with 0xbaddcafe. The
redzone is checked every
time a buffer is allo-
cated or freed.
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Memory Allocation Library Functions umemdebug(3MALOC)
For caches with either
constructors or destruc-
tors, or both,
umemcachealloc(3MALOC)
and
umemcachefree(3MALOC)
apply the cache's con-
structor and destructor,
respectively, instead of
caching constructed
objects. The presence of
assert(3C)s in the des-
tructor verifying that
the buffer is in the
constructed state can be
used to detect any
objects returned in an
improper state. See
umemcachecreate(3MALOC)
for details.
verbose The library writes error
descriptions to standard
error before aborting.
These messages are not
localized.
UMEMLOGING To be enabled, this variable should be set
to a comma-separated list of in-memory logs.
The logs available are:
transaction[=size] If the audit debugging
option is set (see
UMEMDEBUG), the audit
structures from previ-
ous transactions are
entered into this log.
contents[=size] If the audit debugging
option is set, the
contents of objects
are recorded in this
log as they are freed.
If the "contents"
debugging option was
not set, 256 bytes of
each freed buffer are
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Memory Allocation Library Functions umemdebug(3MALOC)
saved.
fail[=size] Records are entered
into this log for
every failed alloca-
tion.
For any of these options, if size is not
specified, the default value of 64k is used.
The size parameter must be an integer that
can be qualified with K, M, G, or T to
specify kilobytes, megabytes, gigabytes, or
terabytes, respectively.
Logs that are not listed or that have either
a size of 0 or an invalid size are disabled.
The log is disabled if during initialization
the requested amount of storage cannot be
allocated.
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Interface Stability Unstable
MT-Level MT-Safe
SEE ALSO
mdb(1), abort(3C), signal(3C), umemcachecreate(3MALOC),
attributes(5)
Solaris Modular Debugger Guide
WARNINGS
When libumem aborts the process using abort(3C), any exist-
ing signal handler for SIGABRT is called. If the signal
handler performs allocations, undefined behavior can result.
NOTES
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Memory Allocation Library Functions umemdebug(3MALOC)
Some of the debugging features work only for allocations
smaller than 16 kilobytes in size. Allocations larger than
16 kilobytes could have reduced support.
Activating any of the library's debugging features could
significantly increase the library's memory footprint and
decrease its performance.
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