memory(3tcl) Tcl Built-In Commands memory(3tcl)
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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 de-
bugging 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 it-
self. 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 ck-
free), 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 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, ev-
ery 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 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 en-
abled, 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 ck-
alloc 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(3tcl)
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