NSLog in ANSI-C

In Objective-C, NSLog is great to debug software.
Similar functions can be used in C, with Mac OS X, by using the ASL - Apple System Log - library.

ASL consists of routines providing an interface to the Apple System Log facility, which is intended to be a replacement for the SysLog API.
It allows client applications to create flexible, structured messages and send them to the syslogd server, where they may undergo additional processing. Messages received by the server are saved in a data store (subject to input filtering constraints).

Here's a example C implementation:

#include <asl.h>
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>

/*******************************************************************************
 * Public functions prototypes
 ******************************************************************************/

#pragma mark - Public functions prototypes -

void CLog(          char * fmt, ... );
void CLogEmergency( char * fmt, ... );
void CLogAlert(     char * fmt, ... );
void CLogCritical(  char * fmt, ... );
void CLogError(     char * fmt, ... );
void CLogWarning(   char * fmt, ... );
void CLogNotice(    char * fmt, ... );
void CLogInfo(      char * fmt, ... );
void CLogDebug(     char * fmt, ... );

/*******************************************************************************
 * C entry point
 ******************************************************************************/

#pragma mark - C entry point -

int main( void )
{
    CLog( "hello, world" );
    return EXIT_SUCCESS;
}

/*******************************************************************************
 * Private functions prototypes
 ******************************************************************************/

#pragma mark - Private functions prototypes -

void __clog_create_client( void );
void __clog_log( int level, char * fmt, va_list ap );

/*******************************************************************************
 * Private macros
 ******************************************************************************/

#pragma mark - Private macros -

#define __CLOG_VARGS_LOG( LEVEL )   \
    va_list ap;                     \
    va_start( ap, fmt );            \
    __clog_log( LEVEL, fmt, ap );   \
    va_end( ap );

#ifndef __bool_true_false_are_defined
    #ifdef _Bool
        #define bool                        _Bool
    #else
        #define bool                        char
    #endif
    #define true                            1
    #define false                           0
    #define __bool_true_false_are_defined   1
#endif

/*******************************************************************************
 * Private variables
 ******************************************************************************/

#pragma mark - Private variables -

static aslclient __clog_client;
static bool      __clog_client_connected = false;

/*******************************************************************************
 * Private functions
 ******************************************************************************/

#pragma mark - Private functions -

void __clog_create_client( void )
{
    __clog_client = asl_open( "CLog", "com.apple.console", ASL_OPT_STDERR | ASL_OPT_NO_DELAY );
}

void __clog_log( int level, char * fmt, va_list ap )
{
    aslmsg msg;
    
    if( __clog_client_connected == false )
    {
        __clog_create_client();
    }
    
    if( __clog_client == NULL )
    {
        fprintf( stderr, "Impossible to create the ASL client\n" );
        exit( EXIT_FAILURE );
    }
    
    
    msg = asl_new( ASL_TYPE_MSG );
    
    asl_set( msg, ASL_KEY_FACILITY, "com.apple.console" );
    asl_vlog( __clog_client, msg, level, fmt, ap );
}

/*******************************************************************************
 * Public functions
 ******************************************************************************/

#pragma mark - Public functions -

void CLog( char * fmt, ... )
{
    __CLOG_VARGS_LOG( ASL_LEVEL_WARNING );
}

void CLogEmergency( char * fmt, ... )
{
    __CLOG_VARGS_LOG( ASL_LEVEL_EMERG );
}

void CLogAlert( char * fmt, ... )
{
    __CLOG_VARGS_LOG( ASL_LEVEL_ALERT );
}

void CLogCritical( char * fmt, ... )
{
    __CLOG_VARGS_LOG( ASL_LEVEL_CRIT );
}

void CLogError( char * fmt, ... )
{
    __CLOG_VARGS_LOG( ASL_LEVEL_ERR );
}

void CLogWarning( char * fmt, ... )
{
    __CLOG_VARGS_LOG( ASL_LEVEL_WARNING );
}

void CLogNotice( char * fmt, ... )
{
    __CLOG_VARGS_LOG( ASL_LEVEL_NOTICE );
}

void CLogInfo( char * fmt, ... )
{
    __CLOG_VARGS_LOG( ASL_LEVEL_INFO );
}

void CLogDebug( char * fmt, ... )
{
    __CLOG_VARGS_LOG( ASL_LEVEL_DEBUG );
}