loghelper

C++14 header-only logging library with pluggable backends.

Features

• Header-only, single file loghelper.hpp
• Compile-time backend selection: spdlog / zlog / fallback (zero dependency)
• Compile-time log level filtering (zero overhead when disabled)
• printf-style API with automatic file/line/function info
• Tagged logging for multi-module systems
• Conditional logging (LOG_*_IF)
• Performance measurement macros (LOG_PERF_START/END)
• INI config file support
• Thread-safe output
• spdlog backend: fmt-style {} placeholders via AMS_* macros

Quick Start

#include "loghelper/loghelper.hpp"

int main() {
    loghelper::LogEngine::Init();  // defaults: console, INFO level

    LOG_INFO("Server started on port %d", 8080);
    LOG_TAG_WARN("NET", "Timeout after %d ms", 500);
    LOG_ERROR("Failed: %s", strerror(errno));

    LOG_PERF_START(task);
    // ... work ...
    LOG_PERF_END(task);

    loghelper::LogEngine::Shutdown();
}

Build

mkdir build && cd build

# spdlog backend (default)
cmake .. -DLOGHELPER_BACKEND=spdlog

# fallback backend (zero dependency)
cmake .. -DLOGHELPER_BACKEND=fallback

# zlog backend (requires system-installed zlog)
cmake .. -DLOGHELPER_BACKEND=zlog

make -j$(nproc)
ctest

CMake Options

Option	Default	Description
LOGHELPER_BACKEND	spdlog	Backend: spdlog, zlog, fallback
LOGHELPER_BUILD_TESTS	ON	Build Catch2 unit tests
LOGHELPER_BUILD_BENCH	ON	Build performance benchmarks
LOGHELPER_BUILD_EXAMPLES	ON	Build demo examples

API Reference

Initialization

// From INI config file
loghelper::LogEngine::Init("logger.cfg");

// Programmatic config
loghelper::LogConfig cfg;
cfg.console_level = loghelper::kDebug;
cfg.enable_file = true;
cfg.file_path = "logs/myapp";
loghelper::LogEngine::Init(cfg);

// Defaults (console only, INFO level)
loghelper::LogEngine::Init();

Log Macros

Macro	Description
LOG_TRACE(fmt, ...)	Trace level
LOG_DEBUG(fmt, ...)	Debug level
LOG_INFO(fmt, ...)	Info level
LOG_WARN(fmt, ...)	Warning level
LOG_ERROR(fmt, ...)	Error level
LOG_FATAL(fmt, ...)	Fatal level
LOG_TAG_*(tag, fmt, ...)	With channel tag
LOG_*_IF(cond, fmt, ...)	Conditional
LOG_PERF_START(name)	Start timer
LOG_PERF_END(name)	End timer, print duration
LOG_ASSERT(cond, fmt, ...)	Debug-only assert

Compile-Time Control

// Set before #include to filter at compile time (zero overhead)
#define LOGHELPER_COMPILE_LEVEL LOGHELPER_LEVEL_INFO
#include "loghelper/loghelper.hpp"
// LOG_TRACE and LOG_DEBUG are now completely removed

Configuration File (INI)

[Log]
ConsoleLevel = 1        ; 0=TRACE 1=DEBUG 2=INFO 3=WARN 4=ERROR 5=FATAL
FileLevel = 0
FilePath = logs/app
FileMaxSizeMB = 100
FileMaxFiles = 5
EnableConsole = 1
EnableFile = 1
EnableSyslog = 0

Performance

See docs/benchmark_report.md for full results.

Metric	fallback	spdlog
Single-thread avg latency	~39 ns	~249 ns
Single-thread throughput	~25.6M msg/s	~4.0M msg/s
4-thread throughput	~166.7M msg/s	~10.1M msg/s
Compile-time filtered	~30 ns (clock noise)	~31 ns (clock noise)

License

MIT