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

______________________________________________________________________________

NAME
       memory - Control Tcl memory debugging capabilities.

SYNOPSIS
       memory option ?arg arg ...?
_________________________________________________________________

DESCRIPTION
       The  memory  command  gives  the	 Tcl developer control of Tcl's memory
       debugging capabilities.	The memory  command  has  several  suboptions,
       which are described below.  It is only available when Tcl has been com‐
       piled 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 packets allocated (the current num‐
	      ber 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 onexit file
	      Causes a list of all allocated memory to be written to the spec‐
	      ified  file  during  the finalization 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 ckalloc's 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 iden‐
	      tify 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)
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