umem_debug(3MALLOC) Memory Allocation Library Functions umem_debug(3MALLOC)
NAME
umem_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
variables.
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 buffers. It also enables an 8-byte redzone after each buffer that contains 0xfeedfacefeed-
faceULL.
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 allocated or freed.
For caches with either constructors or destructors, or both, umem_cache_alloc(3MALLOC) and umem_cache_free(3MALLOC)
apply the cache's constructor 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 inte-
ger 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.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Unstable |
+-----------------------------+-----------------------------+
|MT-Level |MT-Safe |
+-----------------------------+-----------------------------+
SEE ALSO
mdb(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 perfor-
mance.
SunOS 5.10 26 July 2002 umem_debug(3MALLOC)