malloc_history(1) BSD General Commands Manual malloc_history(1)NAMEmalloc_history — Show the malloc allocations that the process has per‐
SYNOPSISmalloc_history pid [-highWaterMark] address [address ...]
malloc_history pid -allBySize [-highWaterMark] [address ...]
malloc_history pid -allByCount [-highWaterMark] [address ...]
malloc_history pid -allEvents [-highWaterMark]
malloc_history pid -callTree [-highWaterMark] [-showContent] [-invert]
[-chargeSystemLibraries] [address ...]
DESCRIPTIONmalloc_history inspects a given process and lists the malloc allocations
performed by it. The target process may be specified by pid or by full
or partial name. malloc_history relies on information provided by the
standard malloc library when malloc stack logging has been enabled for
the target process. See below for further information.
If the -highWaterMark option is passed, malloc_history first scans
through the all malloc stack log records to calculate the "high water
mark" of allocated memory -- i.e., the highest amount of allocated memory
used at any one time by the target process. It then shows information
about the malloc allocations that were live at that time, rather than
currently alive in the target program.
By specifying one or more addresses, malloc_history lists all allocations
and deallocations of any malloc blocks that started at those addresses,
or (starting in Mac OS X 10.6) of any malloc blocks that contained those
addresses. For each allocation, a stack trace describing who called mal‐
loc or free is listed. If you do only wish to see events for malloc
blocks that started at the specified address, you can grep the output for
that address. If -highWaterMark is passed, it only shows allocations and
deallocations up to the high water mark.
Alternatively, the -allBySize and -allByCount options list all alloca‐
tions that are currently live in the target process, or were live at the
high water mark. Frequent allocations from the same point in the program
(that is, the same call stack) are grouped together, and output presented
either from largest allocations to smallest, or most allocations to
least. If you also specify one or more addresses, this output is fil‐
tered to only show information for malloc blocks containing those
The -allEvent option lists all allocation and free events, for all
addresses, up to the current time or to the high water mark. This output
can be voluminous.
The -callTree option generates a call tree of the backtraces of malloc
calls for live allocations in the target process, or for allocations that
were live at the high water mark. The call tree format is similar to the
output from sample(1). The resulting call tree can be filtered or pruned
with the filtercalltree(1) tool for further analysis. Additional options
for the -callTree mode include:
-showContent Show the content of malloc blocks of vari‐
ous types, including C strings, Pascal
strings (with a length byte at the start),
and various objects including NSString,
NSDate, and NSNumber.
-invert Invert the call tree, so that malloc (and
the allocated content, if the -showContent
option was given) show at the top of the
-ignoreThreads Combine the call trees for all threads into
a single call tree.
-collapseRecursion Collapse recursion within the call trees.
-chargeSystemLibraries Remove stack frames from all libraries in
/System and /usr, while still charging
their cost (number of calls, allocation
size, and content) to the callers.
All modes require the standard malloc library's debugging facility to be
turned on. To do this, set either the MallocStackLogging or MallocStack‐
LoggingNoCompact environment variable to 1 in the shell that will run the
program. If MallocStackLogging is used, then when recording events, if
an allocation event for an address is immediately followed by a free
event for the same address, both events are removed from the event log.
If MallocStackLoggingNoCompact is used, then all such immediate alloca‐
tion/free pairs are kept in the event log, which can be useful when exam‐
ining all events for a specific address, or when using the -allEvents
If both MallocStackLogging and MallocStackLoggingNoCompact are set, then
MallocStackLogging takes precedence and MallocStackLoggingNoCompact is
malloc_history is particularly useful for tracking down memory smashers.
Run the program to be inspected with MallocStackLogging or MallocStack‐
LoggingNoCompact defined. Also set the environment variable MallocScrib‐
ble; this causes the malloc library to overwrite freed memory with a
well-known value (0x55), and occasionally checks freed malloc blocks to
make sure the memory has not been overwritten since it was cleared. When
malloc detects the memory has been written, it will print out a warning
that the buffer was modified after being freed. You can then use
malloc_history to find who allocated and freed memory at that address,
and thus deduce what parts of the code might still have a pointer to the
SEE ALSOmalloc(3), heap(1), leaks(1), stringdups(1), vmmap(1), filtercalltree(1),
The Xcode developer tools also include Instruments, a graphical applica‐
tion that can give information similar to that provided by
malloc_history. The Allocations instrument graphically displays dynamic,
real-time information about the object and memory use in an application,
including backtraces of where the allocations occured.
BSD Mar. 16, 2013 BSD