c - 动态字符串列表和 free() 导致应用程序崩溃

Question

我编写了一个简单的 C 代码，该代码应在结构内存储字符串地址 (char*) 列表。该列表是动态的，因此每次添加新字符串时，我都会保留足够的内存来存储所有当前字符串地址以及新字符串地址。然后我释放旧缓冲区并将新缓冲区分配给该结构。问题是它在 free() 上崩溃。

我确信我可以 free() 从 calloc() 获得的确切地址，但它仍然崩溃。

这是输出:

main(3618,0x7fff7a83f300) malloc: *** error for object 0x7f9902404bd0: incorrect checksum for freed object - object was probably modified after being freed.

代码是:

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

typedef struct StructNODE{
    char** stringlist;
    int stringcount;
    struct StructNODE* next;
} NODE;


void Addstring(NODE* node, const char* string)
{
    int currentBufferSize = node->stringcount * sizeof(char*);

    // make room for the current string list plus the new one
    char** addrList = (char**) calloc( 1, currentBufferSize );
    printf("malloc: %d bytes starting at 0x%X\n",currentBufferSize, addrList);

    // copy all current addresses to the new list
    memcpy(addrList, node->stringlist, currentBufferSize);

    printf("freeing mem at 0x%X\n",node->stringlist);
    free(node->stringlist);

    // Append the new address to the end of the address buffer
    addrList[node->stringcount] = (char*)string;

    //make the node point to the new buffer
    node->stringlist = addrList;

    // Increment the string number counter
    node->stringcount++;

}

void PrintStringlist(NODE* node)
{
    int i;
    for ( i=0; i < node->stringcount; i++)
    {
        printf("string %d: %s\n",i, node->stringlist[i]);
    }
}

int main(int argc, char** argv)
{
    NODE* node = (NODE*) calloc(1 , sizeof(NODE));

    Addstring(node, "Lewis Skolnick");
    Addstring(node, "Gilbert Lowe");    
    Addstring(node, "Arnold Poindexter");       
    Addstring(node, "Harold Wormser");
    Addstring(node, "Booger");
    Addstring(node, "Takashi Toshiro");
    Addstring(node, "Lamar Latrelle");
    Addstring(node, "Judy");    

    PrintStringlist(node);

    return 0;
}

我忽略了什么？

Answer 1

您的缓冲区太小 - 您忘记为额外元素添加空间。第一个功能行应为:

    int currentBufferSize = (node->stringcount + 1) * sizeof(char*);