fmt / spdlog Source-Level Deep Analysis

Source path: references/impl/fmt/include/fmt/, references/impl/spdlog/include/spdlog/

fmt is the de facto standard C++ formatting library, directly adopted by the C++20 standard as std::format. spdlog is the most popular logging library, built on top of fmt.

Table of Contents

Chapter	Source Path	Content
fmt Formatting Engine	base.h, format.h	Compile-time format string checking, type-erased tagged union, Dragonbox floating-point
fmt Advanced Features	chrono.h, ranges.h, compile.h	Custom types, compile-time formatting, chrono, ranges
spdlog Architecture	spdlog.h, logger.h, sinks/	Logger/Sink/Formatter, async mode, log level pruning