bionic (3) ckalloc.3tcl.gz

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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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