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memory(n)                                   Tcl Built-In Commands                                  memory(n)



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NAME
       memory - Control Tcl memory debugging capabilities

SYNOPSIS
       memory option ?arg arg ...?
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DESCRIPTION
       The  memory command gives the Tcl developer control of Tcl's memory debugging capabilities.  The mem-ory memory
       ory command has several suboptions, which are described below.  It is only  available  when  Tcl  has
       been  compiled  with  memory  debugging  enabled (when TCL_MEM_DEBUG is defined at compile time), and
       after Tcl_InitMemory has been called.

       memory active file
              Write a list of all currently allocated memory to the specified file.

       memory break_on_malloc count
              After the count allocations have been performed, ckalloc outputs a message to this effect  and
              that  it  is  now  attempting  to  enter  the C debugger.  Tcl will then issue a SIGINT signal
              against itself.  If you are running Tcl under a C debugger, it should then enter the  debugger
              command mode.

       memory info
              Returns a report containing the total allocations and frees since Tcl began, the current pack-ets packets
              ets allocated (the current number of calls to ckalloc not  met  by  a  corresponding  call  to
              ckfree), the current bytes allocated, and the maximum number of packets and bytes allocated.

       memory init [on|off]
              Turn  on  or  off the pre-initialization of all allocated memory with bogus bytes.  Useful for
              detecting the use of uninitialized values.

       memory objs file
              Causes a list of all allocated Tcl_Obj values to be written to the specified file immediately,
              together with where they were allocated.  Useful for checking for leaks of values.

       memory onexit file
              Causes a list of all allocated memory to be written to the specified file during the finaliza-tion finalization
              tion of Tcl's memory subsystem.  Useful for checking that memory is properly cleaned up during
              process exit.

       memory tag string
              Each  packet  of  memory allocated by ckalloc can have associated with it a string-valued tag.
              In the lists of allocated memory generated by memory active and memory  onexit,  the  tag  for
              each  packet is printed along with other information about the packet.  The memory tag command
              sets the tag value for subsequent calls to ckalloc to be string.

       memory trace [on|off]
              Turns memory tracing on or off.  When memory tracing is on, every call  to  ckalloc  causes  a
              line of trace information to be written to stderr, consisting of the word ckalloc, followed by
              the address returned, the amount of memory allocated, and the C filename and  line  number  of
              the code performing the allocation.  For example:

                     ckalloc 40e478 98 tclProc.c 1406

              Calls to ckfree are traced in the same manner.

       memory trace_on_at_malloc count
              Enable  memory  tracing  after  count ckallocs have been performed.  For example, if you enter
              memory trace_on_at_malloc 100, after the 100th call to ckalloc, memory trace information  will
              begin  being  displayed  for  all  allocations  and frees.  Since there can be a lot of memory
              activity before a problem occurs, judicious use of this option can reduce the slowdown  caused
              by  tracing  (and  the  amount of trace information produced), if you can identify a number of
              allocations that occur before the problem sets in.  The current number of  memory  allocations
              that have occurred since Tcl started is printed on a guard zone failure.

       memory validate [on|off]
              Turns memory validation on or off. When memory validation is enabled, on every call to ckalloc
              or ckfree, the guard zones are checked for every piece of memory currently in  existence  that
              was  allocated  by  ckalloc.  This has a large performance impact and should only be used when
              overwrite problems are strongly suspected.  The advantage of  enabling  memory  validation  is
              that  a  guard zone overwrite can be detected on the first call to ckalloc or ckfree after the
              overwrite occurred, rather than when the specific memory with the overwritten guard zone(s) is
              freed, which may occur long after the overwrite occurred.

SEE ALSO
       ckalloc, ckfree, Tcl_ValidateAllMemory, Tcl_DumpActiveMemory, TCL_MEM_DEBUG

KEYWORDS
       memory, debug



Tcl                                                  8.1                                           memory(n)