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c++ - Linux 上的 curl_easy_perform 分段错误

问题描述

我正在开发一个 c++ 应用程序，它使用 curl 来发送 HTTP GET 请求。它在 Windows 上运行良好，但在 Linux (CentOS 7) 上使用 curl_easy_cleanup 时出现分段错误。

下面是我的代码

CURL* curl = NULL;
    curl = curl_easy_init();

    if (curl == NULL)
    {

        this->getBitsLibrary()->writeToLog("Failed to init curl");
        this->getBitsLibrary()->setAlarm("CrashInfo", Alarms::AlarmLevel::Critical, "Failed to init curl for IP lookup");
        return;
    }

    stringstream urlstream;
    string iplookupURL;
    //curlResponse = "";
    urlstream << StaticSettings::IP_Lookup::ipLookupURL << "/" << clientIP << "?access_key="<<StaticSettings::IP_Lookup::api_key;
    iplookupURL = urlstream.str();
    logstream << "Using URL " << iplookupURL << " for IP lookup";
    this->getBitsLibrary()->writeToLog(logstream.str(), "CrashInfo", "performIPLookup");
    logstream.clear();
    logstream.str(string());
    //string response = "";
    this->curlResponse = new string();
    curl_easy_setopt(curl, CURLOPT_URL, iplookupURL.c_str());
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void*)this);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, &curlStaticCallback);



    CURLcode res = curl_easy_perform(curl);
if (res != CURLE_OK)
    {
        logstream << "Failed to perform IP lookup using curl";
        this->getBitsLibrary()->writeToLog(logstream.str(), "CrashInfo", "performIPLookup");
        this->getBitsLibrary()->setAlarm("CrashInfo", Alarms::AlarmLevel::Warning, "Failed to perform IP Lookup. Curl error");
        curl_easy_cleanup(curl);
        return;
    }

    int httpResponseCode = 0;
    curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &httpResponseCode);
    if (httpResponseCode == 200)
    {

        if (!this->curlResponse->empty())
        {
            this->getBitsLibrary()->writeToLog("Processing response for IP lookup");
            rapidjson::Document jsonObject;
            jsonObject.Parse(this->curlResponse->c_str());

            const rapidjson::Value& countryValue = jsonObject["country_name"];
            if (!countryValue.IsNull())
            {
                string country = string(jsonObject["country_name"].GetString());
                this->setCountry(!country.empty() ? country : "N/A");
            }
            else
            {
                this->setCountry("N/A");
            }

            const rapidjson::Value& cityValue = jsonObject["city"];
            if (!cityValue.IsNull())
            {
                string city = string(jsonObject["city"].GetString());
                this->setCity(!city.empty() ? city : "N/A");
            }
            else
            {
                this->setCity("N/A");
            }

            this->getBitsLibrary()->writeToLog("IPLookup performed successfully", "CrashInfo", "performIPLookup");
        }
delete this->curlResponse;
    this->curlResponse = NULL;
    curl_easy_cleanup(curl);

由于 curl 是一个 C 库，我创建了一个静态函数（在 C++ 类之外），如下所示：

size_t curlStaticCallback(void *contents, size_t size, size_t nmemb, void * userp)
{
    CrashInfo *crashInfo = (CrashInfo*)userp;
    crashInfo->curlResponseWriteCallback(contents, size, nmemb, userp);
    return size * nmemb;
}

curl中WRITEFUNCTION调用的上述静态函数。我得到类对象，然后调用 C++ 函数，如下所示：

size_t CrashInfo::curlResponseWriteCallback(void *contents, size_t size, size_t nmemb, void *userp)
{
    curlResponse->append((char*)contents, size * nmemb);
    return size * nmemb;
}

如上所述，这在 Windows 上运行良好，但在 Linux 上运行良好，我得到预期的响应 URL，但是当curl_easy_cleanup被调用时，我得到一个包含以下堆栈的分段错误：

#0  0x00007fe7f45ff2ad in ?? () from /lib64/libstdc++.so.6
#1  0x00007fe7f4661c03 in std::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string() () from /lib64/libstdc++.so.6
#2  0x000000000043f773 in WebManager::CrashInfo::performIPLookup (this=0x7fe7d00020d0, clientIP="192.168.1.96") at CrashInfo.cpp:732
#3  0x000000000043aeb0 in WebManager::CrashInfo::processCrashInfo (this=0x7fe7d00020d0, httpRequest=0x7fe7d00008f0) at CrashInfo.cpp:308
#4  0x00000000004396ee in WebManager::CrashInfo::CrashInfo (this=0x7fe7d00020d0, httpRequest=0x7fe7d00008f0) at CrashInfo.cpp:50
#5  0x000000000046ce23 in WebManager::WebProcessor::processWebSocketData (this=0x7fe7ed841a60, clientpointer=0x7fe7e40008c0, ipAddress=0x7fe7ed8426b8 "192.168.1.96") at WebProcessor.cpp:71
#6  0x0000000000473bd6 in std::_Mem_fn<void (WebManager::WebProcessor::*)(void*, char*)>::operator()<int*, char*, void>(WebManager::WebProcessor*, int*&&, char*&&) const (this=0x7fe7e4000948, __object=0x7fe7ed841a60)
    at /usr/include/c++/4.8.2/functional:601
#7  0x00000000004739fd in std::_Bind_simple<std::_Mem_fn<void (WebManager::WebProcessor::*)(void*, char*)> (WebManager::WebProcessor*, int*, char*)>::_M_invoke<0ul, 1ul, 2ul>(std::_Index_tuple<0ul, 1ul, 2ul>) (this=0x7fe7e4000930)
    at /usr/include/c++/4.8.2/functional:1732
#8  0x00000000004737fd in std::_Bind_simple<std::_Mem_fn<void (WebManager::WebProcessor::*)(void*, char*)> (WebManager::WebProcessor*, int*, char*)>::operator()() (this=0x7fe7e4000930) at /usr/include/c++/4.8.2/functional:1720
#9  0x000000000047372e in std::thread::_Impl<std::_Bind_simple<std::_Mem_fn<void (WebManager::WebProcessor::*)(void*, char*)> (WebManager::WebProcessor*, int*, char*)> >::_M_run() (this=0x7fe7e4000918)
    at /usr/include/c++/4.8.2/thread:115
#10 0x00007fe7f4659070 in ?? () from /lib64/libstdc++.so.6
#11 0x00007fe7f3aaae25 in start_thread () from /lib64/libpthread.so.0
#12 0x00007fe7f3dbdbad in clone () from /lib64/libc.so.6

我已经在 GDB 中查看了 Curl 的内存位置，以查看是否有意外的权利/损坏，但看起来没有任何问题。

标签： c++libcurl

解决方案

我已经解决了问题，这是一个相当奇怪的问题。正如 Michael Doubez 在评论中所说，它不是直接卷曲。我认为它是 curl，因为堆栈轨道中的第二行指向 curl_easy_cleanup，然后顶行是字符串析构函数，所以认为它是 curl。

我在 curl_easy_cleanup 之后放置了一条日志行，它成功记录然后崩溃。curl_easy_cleanup 是该方法中的最后一次调用，并且在函数完成时发生了崩溃。

我最终注释掉了整个函数，然后慢慢地重新添加它的块来确定它是在什么时候导致它崩溃的。

它最终成为了这条线curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &httpResponseCode);。当函数需要一个指向 long 的指针时，我正在传递一个指向 int 的指针。

我纠正了上述问题，现在一切都按预期工作，但不完全确定为什么虽然这没有 1，引发编译器警告，即我传入了错误的类型，以及 2，为什么堆栈跟踪显示字符串被破坏。

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