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 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 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
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
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 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
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.
SEE ALSO¶
ckalloc, ckfree, Tcl_ValidateAllMemory, Tcl_DumpActiveMemory, TCL_MEM_DEBUG
KEYWORDS¶
memory, debug
