使用realloc连接字符串 [英] Using realloc to concat strings

问题描述

我正在尝试合并两个字符串，假设目标"字符串没有足够的空间来添加另一个字符串，因此我正在使用动态数组来解决它.

I'm trying to concat two strings, supposing the "dest" string hasn't enough space to add another one, so I'm using dynamic arrays to solve it.

问题是尝试编译代码时出现的 mremap_chunk 错误.

The problem is a mremap_chunk error when trying to compile the code.

我不知道我要缺少什么，因为realloc调用中放置了所有正确的参数.

I don't know what I'm missing since the realloc call has all the right params place in.

错误:

malloc.c:2869: mremap_chunk: Assertion `((size + offset) & (GLRO (dl_pagesize) - 1)) == 0' failed. 
Aborted (core dumped)

---

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

char *strcatt(char *s1, char *s2)
{
    int a = strlen(s1);
    int b = strlen(s2);
    int i, size_ab = a+b;

    s1 = (char *) realloc (s1, size_ab*sizeof(char));

    for(i=0; i<b; i++) {
        s1[i+a]=s2[i];
    }

    s1[size_ab]='\0';

    return s1;
}


int main()
{
    char s1[]="12345";
    char s2[]="qwerty";

    strcatt(s1,s2);
    printf("%s\n", s1);

    return 0;
}

推荐答案

首先，您将非堆内存视为堆内存，请不要这样做.

First, you are treating non-heap memory as heap memory, don't do that.

第二，您没有在计算中包括终止符的空间.

Second you're not including space for the terminator in the calculation.

还有一些要点:

1. 不要以 str 开头的名称功能，这是保留的名称空间.
2. 缓冲区大小应为 size_t ，而不是 int .
3. 不要转换 malloc()的返回值在C 中.
4. 知道大小后，使用 memcpy()复制内存块.
5. 右侧"字符串应为 const .
6. 处理分配错误的可能性.
7. 我认为按 sizeof(char)(始终为1)进行缩放是一种不好的做法.

1. Don't name functions starting with str, that's a reserved name space.
2. Buffer sizes should be size_t, not int.
3. Don't cast the return value of malloc() in C.
4. Use memcpy() to copy blocks of memory when you know the size.
5. The "right hand side" strings should be const.
6. Deal with the possibility of allocation error.
7. I consider it bad practice to scale by sizeof (char), that's always 1.

假设相同的逻辑，这就是我的写法:

Here's how I would write it, assuming the same logic:

char * my_strcatt(char *s1, const char *s2)
{
    const size_t a = strlen(s1);
    const size_t b = strlen(s2);
    const size_t size_ab = a + b + 1;

    s1 = realloc(s1, size_ab);

    memcpy(s1 + a, s2, b + 1);

    return s1;
}

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