corLog — Logging and Tracing

A comprehensive C logging library with support for multiple message types, fine-grained trace levels, and thread-safe output to files and/or stdout.

• Version: 0.1.0
• Language: C
• License: Apache License 2.0

The only dependency is corBase.

Where it comes from

corLog is ktrace under the cor prefix, copied, not forked: ktrace itself is untouched and keeps serving its own users. It was only ever called ktrace because the name klog was taken; in the coraine stack it is the log, so it is called that.

The renames: KT_E/KT_W/KT_T/... → COR_E/COR_W/COR_T/..., ktInit → corLogInit, ktOut → corLogOut, ktTraceLevelSet → corLogTraceLevelSet (and the rest of ktTraceLevel*), the globals ktVerbose/ktDebug/... → corLogVerbose/corLogDebug/.... A trace level is still a trace level — it is not a log level, and the names say so. KBool became bool.

Features

• Multiple message types - Debug, trace, verbose, info, warning, error, fatal
• Fine-grained trace levels - Up to 3200 individual trace levels
• Thread-safe - Mutex-protected output for multi-threaded applications
• Flexible output - Log to file, stdout, or both simultaneously
• Timestamped - Microsecond precision relative to initialization
• Context-aware - Automatically captures file, line, and function name

API Reference

Initialization

corLogInit

int corLogInit(
    const char* progName,    // Program name (used for log filename)
    const char* logDir,      // Log directory (NULL for stdout only)
    bool       logToScreen, // Echo to stdout in addition to file
    const char* logLevel,    // "ERR", "WARN", "INFO", "VERBOSE", "TRACE", "DEBUG"
    const char* traceLevels, // Trace levels: "5,10,15-20,100"
    bool       verbose,     // Enable verbose output
    bool       debug,       // Enable debug output
    bool       fixme        // Enable FIXME markers
);

Initializes the logging system. Creates <logDir>/<progName>.log, backing up existing logs to .old.

Trace Level Configuration

void corLogTraceLevelSet(const char* levelString);  // "5,10,15-20"
void corLogTraceLevelSetOne(int level);         // Single level (0-3199)
bool corLogTraceLevelCheck(unsigned int level);    // Check if enabled

Logging Macros

COR_D(fmt, ...)             // Debug (temporary, to be removed)
COR_T(level, fmt, ...)      // Trace with level
COR_V(fmt, ...)             // Verbose
COR_I(fmt, ...)             // Info
COR_W(fmt, ...)             // Warning
COR_E(fmt, ...)             // Error
COR_X(exitCode, fmt, ...)   // Fatal error, then exit
COR_F(fmt, ...)             // FIXME marker

// Return variants
COR_RE(retVal, fmt, ...)    // Error, then return value
COR_RVE(fmt, ...)           // Error, then return void

Output Format

<TYPE>: <TIMESTAMP>: <FILE>[<LINE>]: <FUNCTION>: <MESSAGE>

Example:

E: 000012.345: main.c[42]: processRequest: Connection refused
T: 000012.346: parser.c[100]: parse: entering parse loop (5)

Building

make          # the library, and obj/debug/corLogTest - a smoke test, never installed
make clean    # remove build artifacts

Usage Example

#include "corLog/corLog.h"

// Define trace levels for your application
#define TL_PARSE    5
#define TL_NETWORK  10
#define TL_DATABASE 15

int main(int argc, char* argv[])
{
    // Initialize: log to /tmp/myapp.log and stdout, enable trace levels 5,10
    corLogInit("myapp", "/tmp", true, "TRACE", "5,10", true, false, false);

    COR_I("Application started");
    COR_V("Verbose startup info");

    COR_T(TL_PARSE, "Parsing configuration");
    COR_T(TL_NETWORK, "Connecting to server");
    COR_T(TL_DATABASE, "This won't appear - level 15 not enabled");

    if (error_condition) {
        COR_E("Something went wrong: %s", strerror(errno));
        COR_X(1, "Fatal error, exiting"); // Exits with code 1
    }

    COR_I("Application finished");
    return 0;
}

Output

I: 000000.001: main.c[12]: main: Application started
V: 000000.001: main.c[13]: main: Verbose startup info
T: 000000.002: main.c[15]: main: Parsing configuration (5)
T: 000000.002: main.c[16]: main: Connecting to server (10)
I: 000000.050: main.c[24]: main: Application finished

Trace Level Patterns

Trace levels allow fine-grained control over which messages appear:

// Enable individual levels
corLogTraceLevelSet("5,10,100");

// Enable ranges
corLogTraceLevelSet("15-20");

// Combine both
corLogTraceLevelSet("5,10,15-20,100-150");

Use trace levels to control verbosity for different subsystems:

#define TL_HTTP_REQUEST   10
#define TL_HTTP_RESPONSE  11
#define TL_DB_QUERY       20
#define TL_DB_RESULT      21
#define TL_CACHE_HIT      30
#define TL_CACHE_MISS     31

Global Variables

extern bool corLogInfo;      // Info messages enabled
extern bool corLogVerbose;   // Verbose messages enabled
extern bool corLogDebug;     // Debug messages enabled
extern bool corLogFixme;     // FIXME messages enabled

Thread Safety

All logging is protected by a pthread mutex, ensuring log messages from different threads don't interleave.

Dependencies

• corBase - time functions and COR_VEC_SIZE
• pthread library

License

Apache 2.0 © 2019-2026 Ken Zangelin