为什么这个 realloc() 会失败？

Question

我的第一个 C 项目是一个简单的 cURL-like HTTP 客户端，它检索发送到服务器的请求的 headers、内容和状态。到目前为止一直在努力，但还没有完成，我需要一些帮助。内存分配对我来说是一个障碍，目前这个问题是我自己无法解决的。

在一个名为 HTTPresponse *requestHTTPresponse(URLdata *requestDestination) 的函数中，重新分配包含原始 HTTP 响应 headers 和内容的字符串由于某些未知原因而失败。原始 HTTP 响应字符串的指针设置为 NULL，我被迫退出我的程序。 为什么会发生这种行为，我该如何解决？此外，当我编译我的程序时，它有时会冻结并拒绝按预期打印文本或退出，这可能是DNS 挂起或其他一些奇怪的网络问题的结果。也欢迎任何其他建议。

可以找到完整的 C 源代码 here。

HTTPresponse *requestHTTPresponse(URLdata *requestDestination) {
    char ip[INET6_ADDRSTRLEN], *request, *response = malloc(1), *headerTerminator = NULL, *responseTerminator = NULL, *headerString, *contentString, buffer[100];
    int sockfd, bufferLength, responseLength;
    struct addrinfo hints, *servinfo, *p;

    /* Initialize HTTP response structure */
    HTTPresponse *returnresponse = malloc(sizeof(HTTPresponse));
    returnresponse->status = 0;
    returnresponse->headers = NULL;
    returnresponse->content = NULL;

    /* Retrieve IP address of host */
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    if (getaddrinfo(requestDestination->host, requestDestination->port, &hints, &servinfo) != 0) {
        return returnresponse;
    }

    /* Loop through all possible connections */
    for (p = servinfo; p != NULL; p = p->ai_next) {
        if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
            continue;
        }
        if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
            close(sockfd);
            continue;
        }
        break;
    }

    if (p == NULL) {
        return returnresponse;
    }

    /* Print IP address & free server information */
    inet_ntop(p->ai_family, get_in_addr((struct sockaddr*)p->ai_addr), ip, sizeof(ip));
    //printf("The IP address is: %s\n", ip);
    freeaddrinfo(servinfo);

    /* Format HTTP request */
    request = malloc(27 + (int)strlen(requestDestination->path) + (int)strlen(requestDestination->host) * sizeof(char));
    if (request == NULL) {
        printf("Failure to allocate memory.\n");
        exit(1);
    }
    sprintf(request, "GET %s HTTP/1.1\r\nHost: %s\r\n\r\n", (*(requestDestination->path) == 0)?"/":requestDestination->path, requestDestination->host);

    /* Send HTTP request */
    send(sockfd, request, 26 + strlen(requestDestination->path) + strlen(requestDestination->host), 0);
    free(request);

    /* Receive HTTP response */
    do {
        bufferLength = recv(sockfd, buffer, 99, 0);
        if (bufferLength == -1) {
            break;
        }
        responseLength += bufferLength;
        response = realloc(response, (responseLength + 1) * sizeof(char)); //Source of issues
        if (response == NULL) {
            printf("Failure to allocate memory.\n");
            exit(2);
        }
        strncpy(response + responseLength - bufferLength, buffer, bufferLength);
        if (headerTerminator) {
            responseTerminator = strstr(response, "\r\n\r\n");
        } else {
            headerTerminator = strstr(response, "\r\n\r\n");
        }
    } while (responseTerminator == NULL);

    /* Store data in structs */
    headerString = malloc((headerTerminator - response + 1) * sizeof(char));
    if (headerString == NULL) {
        printf("Failure to allocate memory.\n");
        exit(1);
    }
    strncpy(headerString, response, headerTerminator - response);
    contentString = malloc((responseTerminator - headerTerminator) * sizeof(char));
    if (contentString == NULL) {
        printf("Failure to allocate memory.\n");
        exit(1);
    }
    strncpy(contentString, headerTerminator, responseTerminator - headerTerminator);
    returnresponse->headers = generateHeaderList(headerString);
    returnresponse->content = contentString;
    free(response);

    /* Close connection & return HTTP response */
    close(sockfd);
    return returnresponse;
}

Answer 1

确保您的变量已初始化。在最初的问题中，您试图重新分配一个空指针，并且您需要确保将您的 responselength 变量初始化为 0。

----- 编辑 -----

此外，当从网络连接中获取数据时，如果您使用 strcpy 等函数，请确保您的字符串以零结尾。

为什么这个 realloc() 会失败？

Why does this realloc() fail?

c

client

http

realloc