memory - Control Tcl memory debugging capabilities
?arg arg ...
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
has been called.
- memory active file
- Write a list of all currently allocated memory to the specified
- 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 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
- 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 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
- 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