如何正确免费字符**用C [英] How to properly free char** in C

问题描述

我真的已经搞不清楚这个二维字符数组

 的char ** ARG =的malloc（sizeof的（字符*）* ARGC）
的for（int i = 0; I＆LT; ARGC，我++）
  ARG [I] =的malloc（sizeof的（char）的*尺寸）
...
...
 

现在假设经过一系列的操作，我忘了变量ARGC，我怎么能释放这些记忆？
我可以做这样的事情？这是在任何情况下绝对正确的？

 的char ** TMP = ARG;
而（* TMP！= NULL）{
    免费（* TMP）;
    TMP ++;
}
免费（ARG）;
 

解决方案

没有

 而（* TMP！= NULL）{
 

您可能达到上面，你会间接引用的内存还没有被分配到并引发未定义行为的一个点。

或者像建议你可以明确分配 NULL 到最后分配的指针，在这种情况下，它会正常工作。

I have really been confused about this 2D char array

char **arg = malloc(sizeof(char*) * argc)
for (int i = 0; i < argc; i++)
  arg[i] = malloc(sizeof(char) * size)
...
...

Now suppose after a series of operations, I forget the variable argc, how can I free those memory? Can I do something like this? Is this absolutely correct under all circumstances?

char **tmp = arg;
while (*tmp != NULL){
    free(*tmp); 
    tmp++;
}
free(arg);

解决方案

No

while(*tmp != NULL){

you may reach above a point where you will dereference memory which hasn't been assigned to and trigger undefined behaviour.

Or as suggested you can explicitly assign a NULL to the last allocated pointer, and in that case it will work.

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