Logging for C++: Best Libraries and Solutions

Logging for C++: Best Solutions

Logging is a critically important component of any serious C++ project. It helps track program execution, find errors, analyze performance, and audit user actions. Unlike Python, where the built-in logging module is the de facto standard, C++ has no single built-in solution. However, the community has created several powerful and flexible libraries. In this article, we will look at the best of them: spdlog, Google glog, Boost.Log, and Easylogging++.

Criteria for Choosing a Logging Library

Before moving on to the review, it is important to understand what to look for when choosing:

• Performance: minimal impact on application speed.
• Flexibility: ability to configure formats, logging levels (DEBUG, INFO, WARN, ERROR) and outputs (file, console, syslog).
• Ease of Integration: header-only libraries are preferable for small projects.
• Multithreading Support: thread safety and asynchronous writing.
• License: compatibility with commercial projects (MIT, Apache, Boost).

1. spdlog — The Fastest and Most Modern

spdlog is a header-only library (optionally compilable), written in C++11/14/17. It is rightfully considered the most popular due to its lightning speed and minimal memory consumption. spdlog supports asynchronous logging, which is especially important for high-load systems.

Key Features:

• Thread safety out of the box.
• Many sinks: file, console, syslog, rotatable files, daily files.
• Support for custom formatters (based on fmtlib).
• Asynchronous mode with a message queue.
• Conditional logging.

Usage Example:

#include "spdlog/spdlog.h"#include "spdlog/sinks/basic_file_sink.h"

int main() {    // Create a logger that writes to a file    auto file_logger = spdlog::basic_logger_mt("file_logger", "logs/app.log");    spdlog::set_default_logger(file_logger);    spdlog::set_level(spdlog::level::debug);

    // Log messages    spdlog::info("Application started");    spdlog::warn("Suspicious behavior detected: {}", 42);    spdlog::error("Critical error: {}", errno);

    // Asynchronous logging    spdlog::flush_every(std::chrono::seconds(3));    return 0;}

When to choose: for modern projects where speed is critical. Ideal for games, real-time servers, and embedded systems.

2. Google glog — A Time-Tested Standard

Google glog (Google Logging Library) is a library developed by Google for internal use. It is simple, reliable, and used in thousands of projects worldwide. glog does not try to be the fastest, but provides all the necessary functions for logging in production.

Features:

• Automatic log rotation by size.
• Logging levels: INFO, WARNING, ERROR, FATAL (with abort).
• Conditional logging (LOG_IF, LOG_EVERY_N).
• Call stack support on fatal errors.
• Minimal dependency — only pthreads.

Usage Example:

#include <glog/logging.h>

int main(int argc, char* argv[]) {    google::InitGoogleLogging(argv[0]);    FLAGS_log_dir = "./logs";    FLAGS_minloglevel = google::INFO;

    LOG(INFO) << "Server started on port " << 8080;    LOG(WARNING) <