Location

include/mop/log.h   — Public API, macros, log level enum
src/util/log.c       — Default stderr callback, level filtering, dispatch

Overview

The log module provides four severity levels, a callback-based output sink, and both compile-time and runtime level filtering. By default all log messages are written to stderr with file and line information. Applications can install a custom callback to redirect output to any destination.

Types

MopLogLevel

typedef enum MopLogLevel {
    MOP_LOG_DEBUG = 0,
    MOP_LOG_INFO  = 1,
    MOP_LOG_WARN  = 2,
    MOP_LOG_ERROR = 3
} MopLogLevel;

MopLogCallback

typedef void (*MopLogCallback)(MopLogLevel level, const char *file,
                               int line, const char *fmt, va_list args);

Function pointer type for custom log sinks. Parameters:

Functions

mop_log_set_callback

void mop_log_set_callback(MopLogCallback cb);

Installs a custom log callback. All subsequent log messages will be dispatched to cb instead of the default stderr sink. Pass NULL to restore the default behavior. Only one callback is active at a time; setting a new callback replaces the previous one.

mop_log_set_level

void mop_log_set_level(MopLogLevel level);

Sets the minimum runtime log level. Messages with a severity below level are silently discarded. The default level is MOP_LOG_DEBUG (all messages pass). This is a runtime filter and can be changed at any time.

mop_log_emit

void mop_log_emit(MopLogLevel level, const char *file, int line,
                  const char *fmt, ...);

Internal log dispatch function. Checks the message against the runtime level, then forwards to the active callback (or the default stderr sink). Application code should use the convenience macros below rather than calling this directly.

Logging Macros

MOP_DEBUG(fmt, ...)
MOP_INFO(fmt, ...)
MOP_WARN(fmt, ...)
MOP_ERROR(fmt, ...)

Each macro expands to a call to mop_log_emit with the appropriate MopLogLevel, __FILE__, and __LINE__. Arguments follow printf format conventions.

MOP_DEBUG("loaded %u vertices from %s", mesh.vertex_count, path);
MOP_WARN("resolution %d capped to %d", resolution, max);
MOP_ERROR("failed to open file: %s", path);

Compile-Time Filtering

Define MOP_LOG_MIN_LEVEL before including mop/log.h (or via compiler flags) to strip log calls at compile time. Macros for levels below the minimum expand to ((void)0), eliminating both the format string and the function call.

Example: compiling with -DMOP_LOG_MIN_LEVEL=2 strips all debug and info logging from the binary.

Default Behavior

When no custom callback is installed, log messages are written to stderr in this format:

[mop:LEVEL] file.c:42: message text

The level label is right-padded to 5 characters (DEBUG, INFO , WARN , ERROR) for aligned output.

Custom Callback

void my_logger(MopLogLevel level, const char *file,
               int line, const char *fmt, va_list args) {
    /* Write to application log, GUI console, file, etc. */
    char buf[1024];
    vsnprintf(buf, sizeof(buf), fmt, args);
    app_log_write(level, buf);
}

/* Install */
mop_log_set_callback(my_logger);

/* Restore default */
mop_log_set_callback(NULL);

Usage

/* Set runtime level to suppress debug messages */
mop_log_set_level(MOP_LOG_INFO);

/* Log at various levels */
MOP_DEBUG("this will be suppressed");
MOP_INFO("viewport created: %dx%d", width, height);
MOP_WARN("framerate below 30 fps: %.1f", fps);
MOP_ERROR("RHI buffer creation failed");