Memory(3tcl)

NAME
ckalloc, memory, ckfree, Tcl_DisplayMemory, Tcl_InitMemory, Tcl_ValidateAllMemory - 合法的内存分配接口

总览 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
    生成一个报告，包含自从 Tcl 启动以来分配和释放的(内存)总数，当前分配的包(未遇到相应的到 ckfree 的调用的到 ckalloc 的调用的当前数目)的数目，当前分配的字节数，和已分配的包和字节的最大的数目。

memory trace [on|off]
    使内存跟踪开启或关闭。在开启内存跟踪的时候，对 ckalloc 的每次调用都导致向 stderr 写一行跟踪信息，其组成有字 ckalloc，随后是返回的地址，分配的内存总数，和进行分配的 C 文件名和代码的行数。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]
    使内存生效(validation)开启或关闭。在开启内存生效的时候，在对ckalloc 或 ckfree 的每次调用上，检查用 ckalloc 分配的每块现存的内存的守卫区(guard zone)。这有很大的性能影响而只在强烈怀疑有覆写(overwrite)问题的时候才使用。开启内存生效的益处是在覆写发生之后第一次调用 ckalloc 或 ckfree 的时候就能检测到守卫区覆写，而不是在释放有覆写守卫区的内存的时候，释放可能在内存覆写发生之后才发生。

memory trace_on_at_malloc nnn
    在进行了 count 数目 ckalloc 之后启用内存跟踪。例如，如果你键入了 memory trace_on_at_malloc 100，在第 100 次调用 ckalloc 之后，将对所有分配和释放的内存显示内存跟踪信息。因为在一个问题发生之前可能有许多内存活动，如果你能在问题出现( sets in)之前标识出一定数目的分配，决定(judicious)使用这个选项可以减轻跟踪导致的速度变慢(和生成的跟踪信息总数)。在发生一个守卫区错误时，输出自从 Tcl 启动以来发生的内存分配的当前数目。

memory break_on_malloc nnn
    在进行了 count 数目的 ckalloc 分配之后，输出一个(中断)消息，表示它现在想进入 C 调试器。 Tcl 将向自身发出一个 SIGINT 信号。如果你在一个 C 调试器下运行 Tcl，它将接着进入调试器命令模式。

memory display file
    向指定文件写当前所有分配的内存的一个列表。

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.

关键字 KEYWORDS
ckalloc, ckfree, free, memory, malloc

[中文版维护人]
寒蝉退士

[中文版最新更新]
2001/09/28

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