[BUG] Incorrect exception type when using Boost futures

[karzhenkov]

The following program reports an exception of unknown type when REDIS_PLUS_PLUS_ASYNC_FUTURE is set to boost and there is no running Redis server:

#include <sw/redis++/async_redis++.h>
#include <iostream>

int main() {
  sw::redis::AsyncRedis redis("tcp://127.0.0.1:6379");
  try {
    if (auto value = redis.get("key").get()) {
      std::cout << "value: " << *value << std::endl;
    }
  } catch (const sw::redis::Error& e) {
    std::cerr << "[sw::redis::Error] " << e.what() << '\n';
  } catch (const std::exception& e) {
    std::cerr << "[std::exception] " << e.what() << '\n';
  } catch (...) {
    std::cerr << "[unknown error]\n";
  }
}

The output is as follows:

[unknown error]

Without REDIS_PLUS_PLUS_ASYNC_FUTURE, the output looks as expected:

[sw::redis::Error] failed to connect to Redis (127.0.0.1:6379): Connection refused

Environment:

• OS: ubuntu
• Compiler: gcc 13.2.0
• hiredis version: v1.2.0
• redis-plus-plus version: master, commit 5eccac2

Additional context
The problem might be related to using std::exception_ptr where boost::exception_ptr is needed.

[sewenew]

What's your boost version? The minimum version requirement for Boost is 1.55.0.

I'm not sure if this is a duplicated issue with this one.

Regards

[karzhenkov]

Hi, @sewenew. My boost version is 1.74.0, so it should work. In addition, the issue you mentioned is about compile-time error. The problem reported here occurs at runtime.

[sewenew]

Thanks for pointing it out! I'll take a look into it.

Regards

[sewenew]

After some research, I found the problem lies on boost::promise::set(std::exception_ptr).

When something bad happens, e.g. failed to connect to Redis, we call promise::set to report error. When boost enabled, it's boost::promise. However, when we call boost::promise::set(std::exception_ptr), the exception type info loses.

So far, I do not find any cheaper solution to fix it. If you have any idea, feel free to let me know.

Regards