[英]malloc causes segmentation fault in C
I am setting a pointer to pointers like in the code above. 我正在设置指针,如上面的代码中所示。 The problem is that malloc is throwing a segmentation fault no matter what I have tried.
问题是无论我尝试过什么,malloc都会抛出一个分段错误。 Here is the code:
这是代码:
wchar_t **Words ;
int lc = lineCounter() ;
**Words = malloc( lc * sizeof(int) ) ;
if (**Words == NULL) return -1 ;
The lineCounter function is just a function that returns the number of lines in a file. lineCounter函数只是一个返回文件中行数的函数。 So what I try to do is free some memory that is needed to save the pointers to lc number of words.
所以我尝试做的是释放一些内存,将指针保存到lc个单词。
Here is a visual representation of what I have in mind : 以下是我的想法:
Let me explain your code line by line: 让我逐行解释你的代码:
wchar_t **Words ;
It is creating a pointer pointing to a pointer on wchar_t. 它正在创建一个指向wchar_t上指针的指针。 The thing is, at creation it is pointing on a random area in the memory so it may not be yours.
问题是,在创建时它指向内存中的随机区域,因此它可能不属于您。
*Words = malloc( lc * sizeof(int) ) ;
This line dereferences the pointer and modify it's content. 此行取消引用指针并修改其内容。 You're trying to modify a memory area that doesn't belong to you.
您正在尝试修改不属于您的内存区域。
I think that what you want to do is: 我想你想做的是:
wchar_t **Words ;
int lc = lineCounter() ;
Words = malloc( lc * sizeof(wchar_t *) ) ;
if (Words == NULL) return -1 ;
And then malloc all the dimensions in your array. 然后malloc你的数组中的所有维度。
EDIT: 编辑:
You may want to do something like that to correspond to your scheme: 您可能希望执行类似的操作以符合您的方案:
wchar_t **Words ;
int i = 0;
int lc = lineCounter() ;
Words = malloc( lc * sizeof(wchar_t *) ) ;
if (Words == NULL) return -1 ;
while (i < lc)
{
Words[i] = malloc(size_of_a_line * sizeof(wchar_t));
if (words[i] == NULL) return -1;
++i;
}
A pointer refers to a storage location . 指针指的是存储位置 。 A variable is an example of a storage location .
变量是存储位置的示例。
The *
operator takes a pointer and gives you the storage location that the pointer refers to. *
运算符采用指针并为您提供指针所指的存储位置。
words
is a pointer; words
是指针; it refers to a storage location of type pointer to wchar_t
. 它指的是
pointer to wchar_t
的类型pointer to wchar_t
的存储位置。 Since it is not initialized, it is undefined what storage location it refers to. 由于它未初始化,因此未定义它所指的存储位置。
Applying the *
operator takes the pointer and produces the location it refers to; 应用
*
运算符获取指针并生成它所引用的位置; since you haven't said what location it refers to, writing to that location could do anything, including crash. 因为你没有说出它所指的位置,所以写入该位置可以做任何事情,包括崩溃。
You need to make the pointer words
refer to a location before you assign something to *words
. 在为
*words
指定内容之前,需要使指针words
指向某个位置。
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