No way to synchronously flush async logger?

[sketch34]

https://github.com/gabime/spdlog/wiki/7.-Flush-policy

I want to use a spdlog async logger in my boost::assertion_failed_msg implementation. spdlog::shutdown() is not appropriate in this case, I want logging to continue if debugging is continued.

namespace boost
{
    inline void assertion_failed(char const * expr, char const * function, char const * file, long line)
    {
      SPDLOG_ERROR("boost assert failed: '{}' in function {} @ {}:{}", expr, function, file, line);
      assert(false);
    }

    inline void assertion_failed_msg(char const * expr, char const * msg, char const * function, char const * file, long line)
    {
      SPDLOG_ERROR("boost assert msg failed: {}\n\t'{}' in function {} @ {}:{}", msg, expr, function, file, line);
      assert(false);
    }
} // namespace boost

I call spdlog::flush_on() appropriately, but it seems like there is no way to cause the async logger to flush to output before the program is halted by the assert(false).

[gabime]

Right. This is a known issue with the async logger (#1696). I would just put small sleep before the assert (ugly but effective).

[tt4g]

Another way, using spdlog::apply_all() (should use thread-safe sink).

spdlog::apply_all([](std::shared_ptr<logger> logger)
{
    for (auto &sink : logger->sinks()) {
        sink->flush();
    }
});

[gabime]

Another way, using spdlog::apply_all() (should use thread-safe sink

The problem it would be executed before the async queue processed fully.

[tt4g]

That's right.
Since synchronous communication is performed during the execution of asynchronous processing, timing problems will occur.
There is a risk that the flush operation will be completed before some messages are added to sink.