strcat和malloc [英] strcat and malloc

问题描述

当前，我需要将strcat()2个字符串放在一起.问题是我必须做3次. (总共6个串联). 步骤是这样，使用循环重复3次:

Currently, I need to strcat() 2 strings together. The catch is that I have to do this 3 times. (Total of 6 concatenations). The procedure is this, repeated 3 times using loops:

1. 分配一个字符串
2. 使用循环，调用strcat 2次
3. 释放字符串

问题是，即使我释放了字符串并重新分配了内存，strcat似乎仍然继续连接前一个字符串.

The problem is that even after I free the string and re-malloc, the strcat seems to keep on concatenating the previous string.

例如:

AA BB CC DD EE FF的预期输出

• strcat字符串1:AABB
• strcat字符串2:CCDD
• strcat字符串3:EEFF

实际输出:

• strcat字符串1:AABB
• strcat字符串2:AABBCCDD
• strcat字符串3:AABBCCDDEEFF

有人知道为什么要这么做吗?

Does anyone know why it's doing this?

void sendInitialHand(card * deck) {

    char * stringToSend;
    playerNode * curNode;
    curNode = housePlayers.head;

    for (int i=0; i<housePlayers.playerCount; i++) {

        stringToSend = malloc(sizeof(char)*6);

        for (int j=0; j<52; j++) {
            if (deck[j].inPlay == curNode->playerFD) {
                strcat(stringToSend, deck[j].identifier);
            }
        }

        for (int j=0; j<52; j++) {
            if (deck[j].inPlay == 10) {
                strcat(stringToSend, deck[j].identifier);
            }
        }    

        printf("[NETWORK] Send %d the following: %s\n", curNode->playerFD, stringToSend);
        //send(curNode->playerFD, stringToSend, 6, 0);
        free(stringToSend);
        curNode = curNode->next;
    }
}

推荐答案

在ptr=malloc(…)之后，在strcat()之前，用*ptr = '\0';初始化空间. malloc()返回的内存通常不为零.

After ptr=malloc(…), before strcat(), initialize the space with *ptr = '\0';. The memory returned by malloc() is usually not zeroed.

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