Section: Tcl Built-In Commands (n)
memory - Control Tcl memory debugging capabilities
?arg arg ...
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 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
- memory info
Returns a report containing the total allocations and frees since
Tcl began, the current packets 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
- 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 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 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.
ckalloc, ckfree, Tcl_ValidateAllMemory, Tcl_DumpActiveMemory, TCL_MEM_DEBUG