无法释放malloc分配的字符串 [英] Can't free a Malloc'd string

问题描述

这应该是快速的，我想。

This one should be quick, I think.

编辑：这是我的CS113类。我只是需要释放所有内存。如果Valgrind的发现有内存泄漏，我会失分。 ：P

This is for my CS113 class. I just needed to free all the memory. If Valgrind found any memory leaks, I'd lose points. :P

不管怎样，我想通了，它显然只是要求我在主免费的东西，涉及到zero_pad的返回值。有一次，我这样做了，它工作得很好。我想纪念这个岗位作为完整的，如果我知道怎么样。

Regardless, I figured out that it apparently just required me to free stuff in Main that related to the return value of zero_pad. Once I did so, it worked fine. I'd mark this post as "complete" if I knew how.

char *zero_pad(struct cpu_t *cpu, char *string)
{
    char *zero_string = malloc(cpu->word_size + 1); 
    int num_zeros = ((cpu->word_size) - strlen(string));
    int i;

    for(i = 0; i < num_zeros; i++)
    {
        zero_string[i] = '0';
    }

    return strncat(zero_string, string, strlen(string));    
}

我需要释放zero_string，因为我分配它。不过，我不知道怎么样。
如果我释放它我回来之前，我已经失去了数据并不能返回。如果我尝试后释放它，功能已经恢复，因而不能去释放它。

I need to free zero_string, since I allocated it. However, I have no idea how. If I free it before I return, then I've lost that data and can't return it. If I try to free it after, the function has already returned and thus can't go on to freeing it.

我试图用strcpy的字符串复制到zero_string一个新的字符串，但我一定是做错了，因为我刚刚结束了一个巨大的烂摊子。

I tried to use strcpy to copy the string in zero_string into a new string, but I must have been doing it wrong, because I just ended up with a massive mess.

所以，你都觉得是什么？

So, what do you all think?

推荐答案

什么是 CPU-＆GT; word_size ？你确定 CPU-＆GT; word_size＆GT; = strlen的（字符串）在任何情况下？

What is cpu->word_size ? Are you sure that cpu->word_size >= strlen(string) in any case ?

总之，返回缓冲区mallocated所以它是调用者负责释放它。另一种可能性是，如果你知道所需要的最大尺寸为使用静态变量。这是code。

Anyway, the returned buffer is mallocated so it is the caller's responsibility to free it. Another possibility is to use a static variable if you know the maximum size needed. This is the code.

#define MAX_SIZE 128 /* adjust this */
char *zero_pad(struct cpu_t *cpu, char *string)
{
    static char zero_string[MAX_SIZE]; 
    int num_zeros = ((cpu->word_size) - strlen(string));
    int i;

    for(i = 0; i < num_zeros; i++)
    {
        zero_string[i] = '0';
    }

    strcpy(zero_string + i, string); 
    return zero_string;   
}

显然，调用者应该被告知返回的缓冲区始终是相同的（调用者必须复制返回的缓冲区，如果需要，可以使用如的strdup（）后来免费（））。

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