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NAME
ckalloc, memory, ckfree, Tcl_DisplayMemory, Tcl_InitMemory,
Tcl_ValidateAllMemory - 合法的記憶體分配接口
` SYNOPSIS
memory info
memory trace [on|off]
memory validate [on|off]
memory trace_on_at_malloc nnn
memory break_on_malloc nnn
memory display file
#include <tcl.h>
char *
ckalloc (unsigned size)
void
ckfree (char *ptr)
int
Tcl_DumpActiveMemory (char *fileName);
void
Tcl_ValidateAllMemory (char *file,
int line)
void
Tcl_InitMemory (interp)
ARGUMENTS
Tcl_Interp *fileName uint size in
char *ptr in Tcl_Interp *interp in A pointer to the Tcl interpreter.
char *file in The filename of the caller of Tcl_ValidateAllMemory. int
line in The line number of the caller of Tcl_ValidateAllMemory. char
*fileName in File to display list of active memory.
yz DESCRIPTION
ckalloc
This macro allocates memory, in the same manner as malloc, with the
following differences: One, ckalloc checks the value returned from
malloc (it calls malloc for you) and panics if the allocation request
fails. Two, if enabled at compile time, a version of ckalloc with
special memory debugging capabilities replaces the normal version of
ckalloc, which aids in detecting memory overwrites and leaks (repeated
allocations not matched by corresponding frees).
Parameters:
o size - The size of the memory block to be allocated.
Returns:
A pointer to the allocated memory block.
ckfree
This macro frees memory allocated by ckalloc. Like ckalloc, when
memory debugging is enabled, ckfree has enhanced capabilities for
detecting memory overwrites and leaks.
It is very important that you use ckalloc when you need to allocate
memory, and that you use ckfree to free it. Should you use malloc to
allocate and ckfree to free, spurious memory validation errors will
occur when memory debugging is enabled. Should you use free to free
memory allocated by ckalloc, memory corruption will occur when memory
debugging is enabled. Any memory that is to be become the property of
the Tcl interpreter, such as result space, must be allocated with
ckalloc. If it is absolutely necessary for an application to pass back
malloced memory to Tcl, it will work only if Tcl is complied with the
TCL_MEM_DEBUG flag turned off. If you convert your application to use
this facility, it will help you find memory over runs and lost memory.
Note that memory allocated by a C library routine requiring freeing
should still be freed with free, since it calls malloc rather than
ckalloc to do the allocation.
Parmeters:
o ptr - The address of a block to free, as returned by ckalloc.
Tcl_DumpActiveMemory
This function will output a list of all currently allocated memory to
the specified file. The following information is outputted for each
allocated block of memory: starting and ending addresses (excluding
guard zone), size, source file where ckalloc was called to allocate the
block and line number in that file. It is especially useful to call
Tcl_DumpActiveMemory after the Tcl interpreter has been deleted.
Parameters:
o fileName - The name of the file to output the memory list to.
Tcl_ValidateAllMemory
Forces a validation of the guard zones of all currently allocated
blocks of memory. Normally validation of a block occurs when its
freed, unless full validation is enabled, in which case validation of
all blocks occurs when ckalloc and ckfree are called. This function
forces the validation to occur at any point.
Parameters:
o file - The file that this routine is being called from, normally
__FILE__.
o line - The line that this routine is being called from, normally
__LINE__.
ENABLING MEMORY DEBUGGING
To enable memory debugging, Tcl should be recompiled from scratch with
TCL_MEM_DEBUG defined. This will also compile in a non-stub version of
Tcl_InitMemory to add the memory command to Tcl.
TCL_MEM_DEBUG must be either left defined for all modules or undefined
for all modules that are going to be linked together. If they are not,
link errors will occur, with either TclDbCkfree and Tcl_DbCkalloc or
Tcl_Ckalloc and Tcl_Ckfree being undefined.
GUARD ZONES
When memory debugging is enabled, whenever a call to ckalloc is made,
slightly more memory than requested is allocated so the memory
debugging code can keep track of the allocated memory, and also eight-
byte ``guard zones'' are placed in front of and behind the space that
will be returned to the caller. (The size of the guard zone is defined
by the C #define GUARD_SIZE in baseline/src/ckalloc.c -- it can be
extended if you suspect large overwrite problems, at some cost in
performance.) A known pattern is written into the guard zones and, on
a call to ckfree, the guard zones of the space being freed are checked
to see if either zone has been modified in any way. If one has been,
the guard bytes and their new contents are identified, and a ``low
guard failed'' or ``high guard failed'' message is issued. The ``guard
failed'' message includes the address of the memory packet and the file
name and line number of the code that called ckfree. This allows you
to detect the common sorts of one-off problems, where not enough space
was allocated to contain the data written, for example.
THE MEMORY COMMAND
memory options
The Tcl 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.
memory info
生成一茬孎i，包含自從 Tcl
啟動以來分配和釋放的(記憶體)總數，當前分配的包(未遇到相應的到
ckfree 的調用的到 ckalloc
的調用的當前數目)的數目，當前分配的字節數，和已分配的包和字節的最大的數目。
memory trace [on|off]
使記憶體跟蹤開啟或關閉。在開啟記憶體跟蹤的時唌A對 ckalloc
的每次調用都導P向 stderr 寫一行跟蹤信息，其組成有字
ckalloc，隨後是返回的地址，分配的記憶體總數，和進行分配的 C
檔名和代碼的行數。例如:...
ckalloc 40e478 98 tclProc.c 1406
Calls to ckfree are traced in the same manner, except that the
word ckalloc is replaced by the word ckfree.
memory validate [on|off]
使記憶體生效(validation)開啟或關閉。在開啟記憶體生效的時-
唌A在對ckalloc 或 ckfree 的每次調用上，檢查用 ckalloc
分配的每塊現存的記憶體的守衛區(guard
zone)。這有很大的性能影響而只在強烈懷疑有覆寫(overwrite)問題的時-
啎~使用。開啟記憶體生效的益處是在覆寫發生之後第一次調用 ckalloc
或 ckfree 的時-
埭N能檢測到守衛區覆寫，而不是在釋放有覆寫守衛區的記憶體的時-
唌A釋放可能在記憶體覆寫發生之後才發生。
memory trace_on_at_malloc nnn
在進行了 count 數目 ckalloc
之後啟用記憶體跟蹤。例如，如果你鍵入了 memory trace_on_at_malloc
100，在第 100 次調用 ckalloc
之後，將對所有分配和釋放的記憶體顯示記憶體跟蹤信息。因為在一-
荌暋D發生之前可能有釵h記憶體活動，如果你能在問題出現( sets
in)之前標識出一定數目的分配，決定(judicious)使用這-
蚇龠等i以減輕跟蹤導P的速度變慢(和生成的跟蹤信息總數)。在發生一-
茼u衛區錯誤時，輸出自從 Tcl
啟動以來發生的記憶體分配的當前數目。
memory break_on_malloc nnn
在進行了 count 數目的 ckalloc 分配之後，輸出一-
(中斷)消息，表示它現在想進入 C 調試器。 Tcl 將向自巡o出一
SIGINT 信號。如果你在一 C 調試器下運行
Tcl，它將接著進入調試器命令模式。
memory display file
向指定檔案寫當前所有分配的記憶體的一茼C表。
DEBUGGING DIFFICULT MEMORY CORRUPTION PROBLEMS
Normally, Tcl compiled with memory debugging enabled will make it easy
to isolate a corruption problem. Turning on memory validation with the
memory command can help isolate difficult problems. If you suspect (or
know) that corruption is occurring before the Tcl interpreter comes up
far enough for you to issue commands, you can set MEM_VALIDATE define,
recompile tclCkalloc.c and rebuild Tcl. This will enable memory
validation from the first call to ckalloc, again, at a large
performance impact.
If you are desperate and validating memory on every call to ckalloc and
ckfree isn't enough, you can explicitly call Tcl_ValidateAllMemory
directly at any point. It takes a char * and an int which are normally
the filename and line number of the caller, but they can actually be
anything you want. Remember to remove the calls after you find the
problem.
r KEYWORDS
ckalloc, ckfree, free, memory, malloc
[]
Hhh
[]
2001/09/28
m Linux manUpn:
http://cmpp.linuxforum.net