umem_debug(3MALLOC) Memory Allocation Library Functions umem_debug(3MALLOC)NAMEumem_debug - debugging features of the umem library
SYNOPSIS
cc [ flag... ] file... -lumem [ library... ]
#include <umem.h>
DESCRIPTION
The libumem library provides debugging features that detect memory
leaks, buffer overruns, multiple frees, use of uninitialized data, use
of freed data, and many other common programming errors. The activation
of the run-time debugging features is controlled by environment vari‐
ables.
When the library detects an error, it writes a description of the error
to an internal buffer that is readable with the ::umem_status mdb(1)
dcmd and then calls abort(3C).
ENVIRONMENT VARIABLES
UMEM_DEBUG 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 allocation. If
transaction logging (see UMEM_LOGGING) 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 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 UMEM_LOGGING)
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 specified 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 filling allocated and freed
buffers with special patterns to help detect the
use of uninitialized data and previously freed buf‐
fers. It also enables an 8-byte redzone after each
buffer that contains 0xfeedfacefeedfaceULL.
When an object is freed, it is filled with 0xdead‐
beef. 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.
For caches with either constructors or destructors,
or both, umem_cache_alloc(3MALLOC) and
umem_cache_free(3MALLOC) apply the cache's con‐
structor and destructor, respectively, instead of
caching constructed objects. The presence of
assert(3C)s in the destructor verifying that the
buffer is in the constructed state can be used to
detect any objects returned in an improper state.
See umem_cache_create(3MALLOC) for details.
verbose
The library writes error descriptions to standard
error before aborting. These messages are not
localized.
UMEM_LOGGING 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
UMEM_DEBUG), the audit structures from previous
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 saved.
fail[=size]
Records are entered into this log for every failed
allocation.
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 ter‐
abytes, 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.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Unstable │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │MT-Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOmdb(1), abort(3C), signal(3C), umem_cache_create(3MALLOC),
attributes(5)
Solaris Modular Debugger Guide
WARNINGS
When libumem aborts the process using abort(3C), any existing signal
handler for SIGABRT is called. If the signal handler performs alloca‐
tions, undefined behavior can result.
NOTES
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.
SunOS 5.10 26 July 2002 umem_debug(3MALLOC)
