Exception thrown in Aws::Http::CurlHttpClient::OverrideOptionsOnConnectionHandle leaves library in an invalid state

[gmcdorman-opentext]

Describe the bug

When subclassing from Aws::Http::CurlHttpClient and overriding OverrideOptionsOnConnectionHandle, if this method throws an exception:

• The exception is propagated outside the call (so superficially it seems to work as expected)
• The destructor of the base class hangs (acquiring a lock)

Expected Behavior

An exception, including STL exceptions, thrown from the method is handled in a way that cleans up the connection attempt appropriately

Current Behavior

• Exception is propagated out as per standard C++ rules
• Subsequent destruction of the instance hangs

Relevant call stack:

aws-cpp-sdk-core.dll!std::condition_variable::wait(std::unique_lock<std::mutex> & _Lck) Line 599 (c:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.35.32215\include\mutex:599)
aws-cpp-sdk-core.dll!std::condition_variable::wait<bool <lambda>(void)>(std::unique_lock<std::mutex> & _Lck, Aws::Utils::ExclusiveOwnershipResourceManager<void *>::ShutdownAndWait::__l4::bool <lambda>(void) _Pred) Line 605 (c:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.35.32215\include\mutex:605)
aws-cpp-sdk-core.dll!Aws::Utils::ExclusiveOwnershipResourceManager<void *>::ShutdownAndWait(unsigned __int64 resourceCount) Line 106 (c:\.conan\data\aws-sdk-cpp\1.11.116\CRSB\testing\source\src\aws-cpp-sdk-core\include\aws\core\utils\ResourceManager.h:106)
aws-cpp-sdk-core.dll!Aws::Http::CurlHandleContainer::~CurlHandleContainer() Line 28 (c:\.conan\data\aws-sdk-cpp\1.11.116\CRSB\testing\source\src\aws-cpp-sdk-core\source\http\curl\CurlHandleContainer.cpp:28)
aws-cpp-sdk-core.dll!Aws::Http::CurlHttpClient::~CurlHttpClient() (Unknown Source:0)
AgentCurlHttpClient_unit.exe!`AgentCurlHttpClientUnit::demo_failure::test_method'::`2'::TestCurlHttpClient::~TestCurlHttpClient() (Unknown Source:0)

Reproduction Steps

Tested on Windows; setting the native CA option is required there to get the requests to succeed.

class TestCurlHttpClient: public  Aws::Http::CurlHttpClient
{
public:
    TestCurlHttpClient(const Aws::Client::ClientConfiguration& clientConfig): CurlHttpClient(clientConfig)
    {
    }

    void OverrideOptionsOnConnectionHandle(CURL*curlhandle) const override
    {
        auto code = curl_easy_setopt(curlhandle, CURLoption::CURLOPT_SSL_OPTIONS, CURLSSLOPT_NATIVE_CA);
        if (code != CURLE_OK)
        {
            // failed to set native CA
            throw std::runtime_error("Failed to set native CA");
            return;
        }
        if (throw_exception)
        {
            throw std::exception("Demonstration");
        }
    }
    bool throw_exception{false};
};

Aws::Client::ClientConfiguration config;

const char *endpoint = "https://www.google.com";
constexpr Aws::Http::HttpMethod method = Aws::Http::HttpMethod::HTTP_GET;
auto test_class(std::make_unique<TestCurlHttpClient>(config));

auto request_zero(Aws::Http::CreateHttpRequest(Aws::String(endpoint), method, Aws::Utils::Stream::DefaultResponseStreamFactoryMethod));

Aws::Http::CurlHttpClient basic_client_zero(config);
auto response_zero = test_class->MakeRequest(request_zero);
test_class.reset();

test_class = std::make_unique<TestCurlHttpClient>(config);
test_class->throw_exception = true;

auto request_one(Aws::Http::CreateHttpRequest(Aws::String(endpoint), method, Aws::Utils::Stream::DefaultResponseStreamFactoryMethod));
std::shared_ptr<Aws::Http::HttpResponse> response_one;
try
{
    response_one = test_class->MakeRequest(request_one);
}
catch (const std::exception &e)
{
    std::cout << "Exception caught as expected" << std::endl;
}

// Hangs.
test_class.reset();

Possible Solution

try
{
     OverrideOptionsOnConnectionHandle(handle);
}
catch (....)
{
    // cleanup, including unlocking, and put in failure state
    throw;
}

Additional Information/Context

An official mechanism for OverrideOptionsOnConnectionHandle to report a failure would also help.

AWS CPP SDK version used

1.11.116

Compiler and Version used

Visual Studio 2022: Microsoft (R) C/C++ Optimizing Compiler Version 19.41.34123 for x64

Operating System and version

Windows 11

[SergeyRyabinin]

Hi @gmcdorman-opentext,

The SDK by default is built with exceptions disabled, therefore the SDK is unable to catch exceptions thrown by user handlers. Please note that with exceptions disabled, the compiler may also skip exception handling generation, leaving your application process in the undefined behavior state.

This is a feature request to support building with exception handling enabled in the SDK, as well as catching and handling exceptions thrown by different components, including user callbacks/handlers.

Best regards,
Sergey