libcurl-C：未分配指针

Question

我正在编写程序以通过HTTP访问Google Drive REST API。

我正在关注you're not mutating和Google Tutorial

步骤：请求设备和用户密码

curl -d "client_id=client_id&scope=https://www.googleapis.com/auth/drive.file" \
     https://accounts.google.com/o/oauth2/device/code

步骤：轮询Google的授权服务器

curl -d "client_id=<client_id>&client_secret=<client_secret>& \
         code=<device_code>&grant_type=http://oauth.net/grant_type/device/1.0" \
         -H "Content-Type: application/x-www-form-urlencoded" \
         https://www.googleapis.com/oauth2/v4/token

我运行了几次代码，有时效果很好，但是大多数时候失败了，这让我感到沮丧。

我的代码

struct MemoryStruct {
    char *memory;
    size_t size;
};

static size_t WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
{
    size_t realsize = size * nmemb;
    struct MemoryStruct *mem = (struct MemoryStruct *)userp;
    char *ptr = realloc(mem->memory, mem->size + realsize + 1);
    if(ptr == NULL) {
        /* out of memory! */
        printf("not enough memory (realloc returned NULL)\n");
        return 0;
    }
    mem->memory = ptr;
    memcpy(&(mem->memory[mem->size]), contents, realsize);
    mem->size += realsize;
    mem->memory[mem->size] = 0;
    return realsize;
}

int main(void)
{
    CURL *curl_handle, *curl_handle2;
    CURLcode res, res2;

    struct MemoryStruct chunk, chunk2;

    chunk.memory = malloc(1);
    chunk.size = 0;

    curl_global_init(CURL_GLOBAL_ALL);

请求设备和用户代码

    curl_handle = curl_easy_init();

    curl_easy_setopt(curl_handle, CURLOPT_URL, "https://accounts.google.com/o/oauth2/device/code");

    curl_easy_setopt(curl_handle, CURLOPT_POSTFIELDS, "client_id=<my_client_id>.apps.googleusercontent.com&scope=https://www.googleapis.com/auth/drive.file");
    curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
    curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, (void *)&chunk);
    curl_easy_setopt(curl_handle, CURLOPT_USERAGENT, "libcurl-agent/1.0");

    res = curl_easy_perform(curl_handle);

    if(res != CURLE_OK) {
        fprintf(stderr, "curl_easy_perform() failed: %s\n",
                curl_easy_strerror(res));
    }
    else {
        //skip some codes of extracting the user_code here
    }
    curl_easy_cleanup(curl_handle);

    free(chunk.memory);

轮询Google的授权服务器

    printf("Enter below code on 'https://www.google.com/device' :\n");
    printf("%s\n", user_code);
    printf("Press enter when finish\n");
    while( getchar() != '\n' );

    curl_handle2 = curl_easy_init();
    curl_easy_setopt(curl_handle2, CURLOPT_URL, "https://www.googleapis.com/oauth2/v4/token");

    char url[300];
    strcat(url, "client_id=<my_client_id>.apps.googleusercontent.com&client_secret=<my_client_secret>&code=");
    strcat(url, device_code);
    strcat(url, "&grant_type=http://oauth.net/grant_type/device/1.0");

    curl_easy_setopt(curl_handle2, CURLOPT_POSTFIELDS, url);
    curl_easy_setopt(curl_handle2, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
    curl_easy_setopt(curl_handle2, CURLOPT_WRITEDATA, (void *)&chunk2);
    curl_easy_setopt(curl_handle2, CURLOPT_USERAGENT, "libcurl-agent/1.0");

    res2 = curl_easy_perform(curl_handle2);

    if(res2 != CURLE_OK) {
        fprintf(stderr, "curl_easy_perform() failed: %s\n",
                curl_easy_strerror(res2));
    }
    else {
        //do something here
    }
    curl_easy_cleanup(curl_handle2);
    free(chunk2.memory);

此行res = curl_easy_perform(curl_handle);上出现错误

malloc: *** error for object 0x10068a400: pointer being realloc'd was not allocated
test(3989,0x1000ab5c0) malloc: *** set a breakpoint in malloc_error_break to debug

我在运行方案中启用了Address Sanitizer，它显示：

ERROR: AddressSanitizer: attempting double-free on 0x6110000205c0 in thread T0:
2019-04-18 10:17:28.969346+0800 atos[3802:117177] examining /Users/USER/Library/Developer/Xcode/DerivedData/test-dbydzdrhbxzzjcgcmnrcjvlrthal/Build/Products/Debug/test [3789]
    #0 0x1001333d7 in wrap_realloc (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x5c3d7)
    #1 0x1000030f9 in WriteMemoryCallback main.c:30
    #2 0x7fff796da5e4 in Curl_client_chop_write (libcurl.4.dylib:x86_64+0xb5e4)
    #3 0x7fff796f652a in Curl_httpchunk_read (libcurl.4.dylib:x86_64+0x2752a)
    #4 0x7fff796f134b in Curl_readwrite (libcurl.4.dylib:x86_64+0x2234b)
    #5 0x7fff796fa6b9 in multi_runsingle (libcurl.4.dylib:x86_64+0x2b6b9)
    #6 0x7fff796f9b83 in curl_multi_perform (libcurl.4.dylib:x86_64+0x2ab83)
    #7 0x7fff796f2db6 in curl_easy_perform (libcurl.4.dylib:x86_64+0x23db6)
    #8 0x100002363 in main main.c:120
    #9 0x7fff7bcb63d4 in start (libdyld.dylib:x86_64+0x163d4)

0x6110000205c0 is located 0 bytes inside of 246-byte region [0x6110000205c0,0x6110000206b6)
freed by thread T0 here:
    #0 0x10013320d in wrap_free (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x5c20d)
    #1 0x1000021cd in main main.c:98
    #2 0x7fff7bcb63d4 in start (libdyld.dylib:x86_64+0x163d4)