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NAME

       ckalloc,   memory,  ckfree,  Tcl_DisplayMemory,  Tcl_InitMemory,  Tcl_ValidateAllMemory  -
       合法的內存分配接口

總覽 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.

描述 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
              生成一個報告,包含自從                                                          Tcl
              啓動以來分配和釋放的(內存)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]
              使內存跟蹤開啓或關閉。在開啓內存跟蹤的時候,對     ckalloc       的每次調用都導致向
              stderr                                                   寫一行跟蹤信息,其組成有字
              ckalloc,隨後是返回的地址,分配的內存總數,和進行分配的                           C
              文件名和代碼的行數。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]
              使內存生效(validation)開啓或關閉。在開啓內存生效的時候,在對ckallocckfree
              的每次調用上,檢查用           ckalloc           分配的每塊現存的內存的守衛區(guard
              zone)。這有很大的性能影響而只在強烈懷疑有覆寫(overwrite)問題的時候才使用。開啓內存生效的益處是在覆寫發生之後第一次調用
              ckallocckfree
              的時候就能檢測到守衛區覆寫,而不是在釋放有覆寫守衛區的內存的時候,釋放可能在內存覆寫發生之後才發生。

       memory trace_on_at_malloc nnn
              在進行了   count   數目   ckalloc    之後啓用內存跟蹤。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內存顯示內存跟蹤信息。因爲在一個問題發生之前可能有許多內存活動,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)使用這個選項可以減輕跟蹤導致的速度變慢(和生成的跟蹤信息總數)。在發生一個守衛區錯誤時,輸出自從
              Tcl  啓動以來發生的內存分配的當前數目。

       memory break_on_malloc nnn
              在進行了  count   數目的  ckalloc  分配之後,輸出一個(中斷)消息,表示它現在想進入 C
              調試器。   Tcl   將向自身發出一個  SIGINT    信號。如果你在一個   C    調試器下運行
              Tcl,它將接着進入調試器命令模式。

       memory display file
              向指定文件寫當前所有分配的內存的一個列表。

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.

關鍵字 KEYWORDS

       ckalloc, ckfree, free, memory, malloc

[中文版維護人]

       寒蟬退士

[中文版最新更新]

       2001/09/28

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