This manual page is part of Xcode Tools version 3.2

Reading manual pages

malloc_history(1)                        BSD General Commands Manual                       malloc_history(1)

NAME
     malloc_history -- Show the malloc allocations that the process has performed

SYNOPSIS
     malloc_history pid address
     malloc_history pid -all_by_size
     malloc_history pid -all_by_count
     malloc_history pid -all_events

DESCRIPTION
     malloc_history inspects a given process and lists the malloc allocations performed by it.  malloc_his-tory malloc_history
     tory relies on information provided by the standard malloc library when debugging options have been
     turned on.

     By specifying an address, malloc_history lists all allocations and deallocations of any malloc block
     that started at that address, or (starting in Mac OS X 10.6) of any malloc block that contained that
     address.  For each allocation, a stack trace describing who called malloc 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 out-put output
     put for that address.

     Alternatively, the -all_by_size and -all_by_count options list all allocations.  Frequent allocations
     from the same point in the program (that is, the same call stack) are grouped together, and output pre-sented presented
     sented either from largest allocations to smallest, or most allocations to least.

     The -all_events option lists all allocation and free events, for all addresses.  This output can be
     voluminous.

     All modes require the standard malloc library's debugging facility to be turned on.  To do this, set
     either the MallocStackLogging or MallocStackLoggingNoCompact 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 allocation/free
     tion/free pairs are kept in the event log, which can be useful when examining all events for a specific
     address, or when using the -all_events option.

     If both MallocStackLogging and MallocStackLoggingNoCompact are set, then MallocStackLogging takes
     precedence and MallocStackLoggingNoCompact is ignored.

     malloc_history is particularly useful for tracking down memory smashers.  Run the program to be
     inspected with MallocStackLogging or MallocStackLoggingNoCompact defined.  Also set the environment
     variable MallocScribble; 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 over-written overwritten
     written 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 freed structure.

SEE ALSO
     malloc(3), heap(1), leaks(1), vmmap(1), DevToolsSecurity(1)

     The developer tools for the system also include a graphical application, /Developer/Applica-tions/Instruments.app, /Developer/Applications/Instruments.app,
     tions/Instruments.app, that provides instruments that give information similar to that provided by
     malloc_history. The ObjectAlloc instrument graphically displays dynamic, real-time information about
     the object and memory use in an application, including backtraces of where the allocations occured.

BSD                                             Oct. 4, 2008                                             BSD