clog is a single‑header, thread‑safe logging library for C, offering timestamped, context‑rich output with configurable levels and color modes. It works on POSIX and Windows, and requires no dynamic allocations in the hot path.

• Log Levels: TRACE, DEBUG, INFO, WARN, ERROR, FATAL
• Thread Safety: Uses Windows Critical Sections, C11 atomics, or GCC/Clang spin-locks; fallback to no-op in single-threaded builds
• Signal Safety: Provides a minimal, async-signal-safe logging function clog_signal_log for use in signal handlers
• Color Modes:
  • Auto-detect (ANSI on POSIX TTYs or modern Windows consoles)
  • Force ANSI escapes
  • Force Windows Console API
  • Always/never color
• Contextual Output: Outputs timestamp, level tag, message, and optional (file:line in function) location info
• Customizable:
  • clog_set_level(...) to filter by minimum level
  • clog_set_color_mode(...) to override color behavior
  • clog_set_output(...) to redirect logs to any FILE*
• Performance-oriented: Pre-allocated buffers, no malloc in log path
• Portable: Works on Linux, macOS, Windows (compatible with MSVC, GCC, Clang)

• C compiler supporting C11 (optional)
• POSIX or Win32 API for threading and console handling

git clone https://github.com/0xA1M/clog.git
cd clog

Then copy clog.h into your project:

#include "clog.h"

INFO("Server started on port %d", port);
WARN("Low disk space: %d%% remaining", percent);
ERROR("Failed to open file: %s", strerror(errno));
DEBUG("Cache hit for key '%s'", key);
TRACE("Entering function %s", __func__);
FATAL("Unexpected null pointer");

Set minimum log level (default is INFO):

clog_set_level(CLOG_DEBUG);

Control color output (default is CLOG_COLOR_AUTO):

clog_set_color_mode(CLOG_COLOR_NEVER);
clog_set_color_mode(CLOG_COLOR_ALWAYS);
clog_set_color_mode(CLOG_COLOR_ANSI);
clog_set_color_mode(CLOG_COLOR_WIN32);

Redirect log output (default is stdout):

FILE *fp = fopen("app.log", "w");
clog_set_output(fp);
// ... logging calls ...
fclose(fp);

⚠️ Note: If you redirect output to a file, you should disable colors using clog_set_color_mode(CLOG_COLOR_NEVER) as ANSI escape codes may not render properly in files. ✅ TODO: Improve color handling for file outputs.

Cleanup (optional, automatically called via atexit):

clog_cleanup();

void clog_set_level(clog_level_t level);
void clog_set_color_mode(clog_color_mode_t mode);
void clog_set_output(FILE *fp);
void clog_cleanup(void);
void clog_signal_log(const char *message); // Async-signal-safe, minimal logging to stderr

enum clog_level_t {
    CLOG_TRACE, CLOG_DEBUG, CLOG_INFO,
    CLOG_WARN,  CLOG_ERROR, CLOG_FATAL
};

enum clog_color_mode_t {
    CLOG_COLOR_AUTO, CLOG_COLOR_NEVER,
    CLOG_COLOR_ALWAYS, CLOG_COLOR_ANSI,
    CLOG_COLOR_WIN32
};

All log macros expand to clog_log(...) and automatically capture file, line, and function.

The test suite lives under tests/ and covers:

• Basic functionality and level filtering
• Memory-safety and buffer limits
• Signal-handler safety
• Thread-safety (requires pthreads)
• Performance benchmarks
• Configuration and output redirection

make test

✅ clog is tested on Linux (x86_64) with:

• GCC, Clang compilers
• glibc and musl C libraries
• Both multi-threaded and single-threaded builds
• Modern terminal emulators with ANSI support (GNOME Terminal, Alacritty, etc.)

⚠️ Support for Windows is implemented but not yet fully tested in production. If you use it on Windows, feedback and patches are welcome!

See tests/runner.c for full test coverage and usage examples.

1. Fork the repo
2. Create your branch: git checkout -b feature/foo
3. Commit your changes
4. Push: git push origin feature/foo
5. Open a Pull Request

✅ Please include tests and make sure all tests pass before submitting.

MIT License. See LICENSE for details.