syslog_sink should be a bit more open to modifications

[Silex]

Hello,

I'm using spdlog on a device where syslog is weirdly configured: no LOG_TRACE/LOG_DEBUG support. I cannot change this.

So my idea was to reuse https://github.com/gabime/spdlog/blob/v1.x/include/spdlog/sinks/syslog_sink.h like so

template <typename Mutex>
class axis_syslog_sink : public spdlog::sinks::syslog_sink<Mutex>
{

public:

  using spdlog::sinks::syslog_sink<Mutex>::syslog_sink; // Inherit constructors

protected:

  int syslog_prio_from_level(const spdlog::details::log_msg& msg) const {
    if (msg.level == spdlog::level::trace || msg.level == spdlog::level::debug)
      return LOG_INFO;
    return spdlog::sinks::syslog_sink<Mutex>::syslog_prio_from_level(msg);
  }

};

But it does not work because syslog_prio_from_level is not virtual. If syslog_levels_ was protected and/or modifiable from the public interface I could also make it work.

So, being stuck I had to copy-paste-adapt the whole class.

I'd understand if you don't really want to support this weird use case but with a tiny bit of modifications I could drop the custom class entirely.

[gabime]

PR to mark syslog_prio_from_level as virtual is welcome

[Silex]

Continuing in #3124

[Silex]

For those which it might help, here's the final class after the PR was accepted:

#pragma once

#include <mutex>

#include <spdlog/spdlog.h>
#include <spdlog/sinks/syslog_sink.h>

// Custom syslog sink that logs debug and trace messages as LOG_INFO
template <typename Mutex>
struct axis_syslog_sink : public spdlog::sinks::syslog_sink<Mutex>
{
  axis_syslog_sink(std::string ident, int syslog_option, int syslog_facility, bool enable_formatting);
};

template <typename Mutex>
inline axis_syslog_sink<Mutex>::axis_syslog_sink(std::string ident, int syslog_option, int syslog_facility, bool enable_formatting)
: spdlog::sinks::syslog_sink<Mutex>(ident, syslog_option, syslog_facility, enable_formatting)
{
  auto& levels = spdlog::sinks::syslog_sink<Mutex>::syslog_levels_;
  levels[spdlog::level::trace] = LOG_INFO;
  levels[spdlog::level::debug] = LOG_INFO;
}

using axis_syslog_sink_mt = axis_syslog_sink<std::mutex>;
using axis_syslog_sink_st = axis_syslog_sink<spdlog::details::null_mutex>;