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memory(n) - memory, memory - Control Tcl memory debugging capabilities - man n memory

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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(1,2,n)), and after Tcl_InitMemory has been called.

       memory active file(1,n)
              Write  a list of all currently allocated memory to the specified
              file(1,n).

       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(2,7)  against
              itself.   If  you  are running Tcl under a C debugger, it should
              then enter the debugger command mode.

       memory info(1,5,n)
              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(1,n)
              Causes a list of all allocated memory to be written to the spec-
              ified  file(1,n)  during  the finalization of Tcl's memory subsystem.
              Useful for checking that memory is properly  cleaned  up  during
              process exit.

       memory tag string(3,n)
              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(3,n).

       memory trace(3x,n,3x _nc_tracebits) [on|off]
              Turns memory tracing on or off.   When  memory  tracing  is  on,
              every  call  to ckalloc causes a line of trace(3x,n,3x _nc_tracebits) 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(1,8)
              the same manner.

       memory trace_on_at_malloc count
              Enable memory tracing after count ckalloc's have been performed.
              For  example,  if(3,n) you enter memory trace_on_at_malloc 100, after
              the 100th call to ckalloc, memory trace(3x,n,3x _nc_tracebits) 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(3x,n,3x _nc_tracebits) information produced), if(3,n) 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(1,8) 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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