path: root/src/logging.c

/*! \file logging.c
 * Debugging/Logging support code. */
/*
 * (C) 2008-2010 by Harald Welte <laforge@gnumonks.org>
 * (C) 2008 by Holger Hans Peter Freyther <zecke@selfish.org>
 * All Rights Reserved
 *
 * SPDX-License-Identifier: GPL-2.0+
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */

/*! \addtogroup logging
 * @{
 * libosmocore Logging sub-system
 *
 * \file logging.c */

#include "../config.h"

#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>

#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif
#include <time.h>
#include <sys/time.h>
#include <errno.h>

#include <osmocom/core/talloc.h>
#include <osmocom/core/utils.h>
#include <osmocom/core/logging.h>
#include <osmocom/core/timer.h>

#include <osmocom/vty/logging.h>	/* for LOGGING_STR. */

osmo_static_assert(_LOG_CTX_COUNT <= ARRAY_SIZE(((struct log_context*)NULL)->ctx),
		   enum_logging_ctx_items_fit_in_struct_log_context);
osmo_static_assert(_LOG_FLT_COUNT <= ARRAY_SIZE(((struct log_target*)NULL)->filter_data),
		   enum_logging_filters_fit_in_log_target_filter_data);
osmo_static_assert(_LOG_FLT_COUNT <= 8*sizeof(((struct log_target*)NULL)->filter_map),
		   enum_logging_filters_fit_in_log_target_filter_map);

struct log_info *osmo_log_info;

static struct log_context log_context;
static void *tall_log_ctx = NULL;
LLIST_HEAD(osmo_log_target_list);

#define LOGLEVEL_DEFS	6	/* Number of loglevels.*/

static const struct value_string loglevel_strs[LOGLEVEL_DEFS+1] = {
	{ 0,		"EVERYTHING" },
	{ LOGL_DEBUG,	"DEBUG" },
	{ LOGL_INFO,	"INFO" },
	{ LOGL_NOTICE,	"NOTICE" },
	{ LOGL_ERROR,	"ERROR" },
	{ LOGL_FATAL,	"FATAL" },
	{ 0, NULL },
};

#define INT2IDX(x)	(-1*(x)-1)
static const struct log_info_cat internal_cat[OSMO_NUM_DLIB] = {
	[INT2IDX(DLGLOBAL)] = {	/* -1 becomes 0 */
		.name = "DLGLOBAL",
		.description = "Library-internal global log family",
		.loglevel = LOGL_NOTICE,
		.enabled = 1,
	},
	[INT2IDX(DLLAPD)] = {	/* -2 becomes 1 */
		.name = "DLLAPD",
		.description = "LAPD in libosmogsm",
		.loglevel = LOGL_NOTICE,
		.enabled = 1,
	},
	[INT2IDX(DLINP)] = {
		.name = "DLINP",
		.description = "A-bis Intput Subsystem",
		.loglevel = LOGL_NOTICE,
		.enabled = 1,
	},
	[INT2IDX(DLMUX)] = {
		.name = "DLMUX",
		.description = "A-bis B-Subchannel TRAU Frame Multiplex",
		.loglevel = LOGL_NOTICE,
		.enabled = 1,
	},
	[INT2IDX(DLMI)] = {
		.name = "DLMI",
		.description = "A-bis Input Driver for Signalling",
		.enabled = 0, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLMIB)] = {
		.name = "DLMIB",
		.description = "A-bis Input Driver for B-Channels (voice)",
		.enabled = 0, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLSMS)] = {
		.name = "DLSMS",
		.description = "Layer3 Short Message Service (SMS)",
		.enabled = 1, .loglevel = LOGL_NOTICE,
		.color = "\033[1;38m",
	},
	[INT2IDX(DLCTRL)] = {
		.name = "DLCTRL",
		.description = "Control Interface",
		.enabled = 1, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLGTP)] = {
		.name = "DLGTP",
		.description = "GPRS GTP library",
		.enabled = 1, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLSTATS)] = {
		.name = "DLSTATS",
		.description = "Statistics messages and logging",
		.enabled = 1, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLGSUP)] = {
		.name = "DLGSUP",
		.description = "Generic Subscriber Update Protocol",
		.enabled = 1, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLOAP)] = {
		.name = "DLOAP",
		.description = "Osmocom Authentication Protocol",
		.enabled = 1, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLSS7)] = {
		.name = "DLSS7",
		.description = "libosmo-sigtran Signalling System 7",
		.enabled = 1, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLSCCP)] = {
		.name = "DLSCCP",
		.description = "libosmo-sigtran SCCP Implementation",
		.enabled = 1, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLSUA)] = {
		.name = "DLSUA",
		.description = "libosmo-sigtran SCCP User Adaptation",
		.enabled = 1, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLM3UA)] = {
		.name = "DLM3UA",
		.description = "libosmo-sigtran MTP3 User Adaptation",
		.enabled = 1, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLMGCP)] = {
		.name = "DLMGCP",
		.description = "libosmo-mgcp Media Gateway Control Protocol",
		.enabled = 1, .loglevel = LOGL_NOTICE,
	},
};

/*! descriptive string for each log level */
/* You have to keep this in sync with the structure loglevel_strs. */
static const char *loglevel_descriptions[LOGLEVEL_DEFS+1] = {
	"Don't use. It doesn't log anything",
	"Log debug messages and higher levels",
	"Log informational messages and higher levels",
	"Log noticeable messages and higher levels",
	"Log error messages and higher levels",
	"Log only fatal messages",
	NULL,
};

static void assert_loginfo(const char *src)
{
	if (!osmo_log_info) {
		fprintf(stderr, "ERROR: osmo_log_info == NULL! "
			"You must call log_init() before using logging in %s()!\n", src);
		OSMO_ASSERT(osmo_log_info);
	}
}

/* special magic for negative (library-internal) log subsystem numbers */
static int subsys_lib2index(int subsys)
{
	return (subsys * -1) + (osmo_log_info->num_cat_user-1);
}

/*! Parse a human-readable log level into a numeric value
 *  \param lvl[in] zero-terminated string containing log level name
 *  \returns numeric log level
 */
int log_parse_level(const char *lvl)
{
	return get_string_value(loglevel_strs, lvl);
}

/*! convert a numeric log level into human-readable string
 *  \param lvl[in] numeric log level
 *  \returns zero-terminated string (log level name)
 */
const char *log_level_str(unsigned int lvl)
{
	return get_value_string(loglevel_strs, lvl);
}

/*! parse a human-readable log category into numeric form
 *  \param[in] category human-readable log category name
 *  \returns numeric category value, or -EINVAL otherwise
 */
int log_parse_category(const char *category)
{
	int i;

	assert_loginfo(__func__);

	for (i = 0; i < osmo_log_info->num_cat; ++i) {
		if (osmo_log_info->cat[i].name == NULL)
			continue;
		if (!strcasecmp(osmo_log_info->cat[i].name+1, category))
			return i;
	}

	return -EINVAL;
}

/*! parse the log category mask
 *  \param[in] target log target to be configured
 *  \param[in] _mask log category mask string
 *
 * The format can be this: category1:category2:category3
 * or category1,2:category2,3:...
 */
void log_parse_category_mask(struct log_target* target, const char *_mask)
{
	int i = 0;
	char *mask = strdup(_mask);
	char *category_token = NULL;

	assert_loginfo(__func__);

	/* Disable everything to enable it afterwards */
	for (i = 0; i < osmo_log_info->num_cat; ++i)
		target->categories[i].enabled = 0;

	category_token = strtok(mask, ":");
	OSMO_ASSERT(category_token);
	do {
		for (i = 0; i < osmo_log_info->num_cat; ++i) {
			size_t length, cat_length;
			char* colon = strstr(category_token, ",");

			if (!osmo_log_info->cat[i].name)
				continue;

			length = strlen(category_token);
			cat_length = strlen(osmo_log_info->cat[i].name);

			/* Use longest length not to match subocurrences. */
			if (cat_length > length)
				length = cat_length;

			if (colon)
			    length = colon - category_token;

			if (strncasecmp(osmo_log_info->cat[i].name,
					category_token, length) == 0) {
				int level = 0;

				if (colon)
					level = atoi(colon+1);

				target->categories[i].enabled = 1;
				target->categories[i].loglevel = level;
			}
		}
	} while ((category_token = strtok(NULL, ":")));

	free(mask);
}

static const char* color(int subsys)
{
	if (subsys < osmo_log_info->num_cat)
		return osmo_log_info->cat[subsys].color;

	return NULL;
}

static const struct value_string level_colors[] = {
	{ LOGL_DEBUG, "\033[1;34m" },
	{ LOGL_INFO, "\033[1;32m" },
	{ LOGL_NOTICE, "\033[1;33m" },
	{ LOGL_ERROR, "\033[1;31m" },
	{ LOGL_FATAL, "\033[1;31m" },
	{ 0, NULL }
};

static const char *level_color(int level)
{
	const char *c = get_value_string_or_null(level_colors, level);
	if (!c)
		return get_value_string(level_colors, LOGL_FATAL);
	return c;
}

const char* log_category_name(int subsys)
{
	if (subsys < osmo_log_info->num_cat)
		return osmo_log_info->cat[subsys].name;

	return NULL;
}

static void _output(struct log_target *target, unsigned int subsys,
		    unsigned int level, const char *file, int line, int cont,
		    const char *format, va_list ap)
{
	char buf[4096];
	int ret, len = 0, offset = 0, rem = sizeof(buf);
	const char *c_subsys = NULL;

	/* are we using color */
	if (target->use_color) {
		c_subsys = color(subsys);
		if (c_subsys) {
			ret = snprintf(buf + offset, rem, "%s", c_subsys);
			if (ret < 0)
				goto err;
			OSMO_SNPRINTF_RET(ret, rem, offset, len);
		}
	}
	if (!cont) {
		if (target->print_ext_timestamp) {
			struct tm tm;
			struct timeval tv;
			osmo_gettimeofday(&tv, NULL);
			localtime_r(&tv.tv_sec, &tm);
			ret = snprintf(buf + offset, rem, "%04d%02d%02d%02d%02d%02d%03d ",
					tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
					tm.tm_hour, tm.tm_min, tm.tm_sec,
					(int)(tv.tv_usec / 1000));
			if (ret < 0)
				goto err;
			OSMO_SNPRINTF_RET(ret, rem, offset, len);
		} else if (target->print_timestamp) {
			char *timestr;
			time_t tm;
			tm = time(NULL);
			timestr = ctime(&tm);
			timestr[strlen(timestr)-1] = '\0';
			ret = snprintf(buf + offset, rem, "%s ", timestr);
			if (ret < 0)
				goto err;
			OSMO_SNPRINTF_RET(ret, rem, offset, len);
		}
		if (target->print_category) {
			ret = snprintf(buf + offset, rem, "%s%s%s%s ",
				       target->use_color ? level_color(level) : "",
				       log_category_name(subsys),
				       target->use_color ? "\033[0;m" : "",
				       c_subsys ? c_subsys : "");
			if (ret < 0)
				goto err;
			OSMO_SNPRINTF_RET(ret, rem, offset, len);
		}
		if (target->print_level) {
			ret = snprintf(buf + offset, rem, "%s%s%s%s ",
				       target->use_color ? level_color(level) : "",
				       log_level_str(level),
				       target->use_color ? "\033[0;m" : "",
				       c_subsys ? c_subsys : "");
			if (ret < 0)
				goto err;
			OSMO_SNPRINTF_RET(ret, rem, offset, len);
		}
		if (target->print_category_hex) {
			ret = snprintf(buf + offset, rem, "<%4.4x> ", subsys);
			if (ret < 0)
				goto err;
			OSMO_SNPRINTF_RET(ret, rem, offset, len);
		}
		switch (target->print_filename2) {
		case LOG_FILENAME_NONE:
			break;
		case LOG_FILENAME_PATH:
			ret = snprintf(buf + offset, rem, "%s:%d ", file, line);
			if (ret < 0)
				goto err;
			OSMO_SNPRINTF_RET(ret, rem, offset, len);
			break;
		}
	}
	ret = vsnprintf(buf + offset, rem, format, ap);
	if (ret < 0)
		goto err;
	OSMO_SNPRINTF_RET(ret, rem, offset, len);

	if (target->use_color) {
		ret = snprintf(buf + offset, rem, "\033[0;m");
		if (ret < 0)
			goto err;
		OSMO_SNPRINTF_RET(ret, rem, offset, len);
	}
err:
	buf[sizeof(buf)-1] = '\0';
	target->output(target, level, buf);
}

/* Catch internal logging category indexes as well as out-of-bounds indexes.
 * For internal categories, the ID is negative starting with -1; and internal
 * logging categories are added behind the user categories. For out-of-bounds
 * indexes, return the index of DLGLOBAL. The returned category index is
 * guaranteed to exist in osmo_log_info, otherwise the program would abort,
 * which should never happen unless even the DLGLOBAL category is missing. */
static inline int map_subsys(int subsys)
{
	/* Note: comparing signed and unsigned integers */

	if (subsys > 0 && ((unsigned int)subsys) >= osmo_log_info->num_cat_user)
		subsys = DLGLOBAL;

	if (subsys < 0)
		subsys = subsys_lib2index(subsys);

	if (subsys < 0 || subsys >= osmo_log_info->num_cat)
		subsys = subsys_lib2index(DLGLOBAL);

	OSMO_ASSERT(!(subsys < 0 || subsys >= osmo_log_info->num_cat));

	return subsys;
}

static inline bool should_log_to_target(struct log_target *tar, int subsys,
					int level)
{
	struct log_category *category;

	category = &tar->categories[subsys];

	/* subsystem is not supposed to be logged */
	if (!category->enabled)
		return false;

	/* Check the global log level */
	if (tar->loglevel != 0 && level < tar->loglevel)
		return false;

	/* Check the category log level */
	if (tar->loglevel == 0 && category->loglevel != 0 &&
	    level < category->loglevel)
		return false;

	/* Apply filters here... if that becomes messy we will
	 * need to put filters in a list and each filter will
	 * say stop, continue, output */
	if ((tar->filter_map & (1 << LOG_FLT_ALL)) != 0)
		return true;

	if (osmo_log_info->filter_fn)
		return osmo_log_info->filter_fn(&log_context, tar);

	/* TODO: Check the filter/selector too? */
	return true;
}

/*! vararg version of logging function
 *  \param[in] subsys Logging sub-system
 *  \param[in] level Log level
 *  \param[in] file name of source code file
 *  \param[in] cont continuation (1) or new line (0)
 *  \param[in] format format string
 *  \param[in] ap vararg-list containing format string arguments
 */
void osmo_vlogp(int subsys, int level, const char *file, int line,
		int cont, const char *format, va_list ap)
{
	struct log_target *tar;

	subsys = map_subsys(subsys);

	llist_for_each_entry(tar, &osmo_log_target_list, entry) {
		va_list bp;

		if (!should_log_to_target(tar, subsys, level))
			continue;

		/* According to the manpage, vsnprintf leaves the value of ap
		 * in undefined state. Since _output uses vsnprintf and it may
		 * be called several times, we have to pass a copy of ap. */
		va_copy(bp, ap);
		if (tar->raw_output)
			tar->raw_output(tar, subsys, level, file, line, cont, format, bp);
		else
			_output(tar, subsys, level, file, line, cont, format, bp);
		va_end(bp);
	}
}

/*! logging function used by DEBUGP() macro
 *  \param[in] subsys Logging sub-system
 *  \param[in] file name of source code file
 *  \param[in] cont continuation (1) or new line (0)
 *  \param[in] format format string
 */
void logp(int subsys, const char *file, int line, int cont,
	  const char *format, ...)
{
	va_list ap;

	va_start(ap, format);
	osmo_vlogp(subsys, LOGL_DEBUG, file, line, cont, format, ap);
	va_end(ap);
}

/*! logging function used by LOGP() macro
 *  \param[in] subsys Logging sub-system
 *  \param[in] level Log level
 *  \param[in] file name of source code file
 *  \param[in] cont continuation (1) or new line (0)
 *  \param[in] format format string
 */
void logp2(int subsys, unsigned int level, const char *file, int line, int cont, const char *format, ...)
{
	va_list ap;

	va_start(ap, format);
	osmo_vlogp(subsys, level, file, line, cont, format, ap);
	va_end(ap);
}

/*! Register a new log target with the logging core
 *  \param[in] target Log target to be registered
 */
void log_add_target(struct log_target *target)
{
	llist_add_tail(&target->entry, &osmo_log_target_list);
}

/*! Unregister a log target from the logging core
 *  \param[in] target Log target to be unregistered
 */
void log_del_target(struct log_target *target)
{
	llist_del(&target->entry);
}

/*! Reset (clear) the logging context */
void log_reset_context(void)
{
	memset(&log_context, 0, sizeof(log_context));
}

/*! Set the logging context
 *  \param[in] ctx_nr logging context number
 *  \param[in] value value to which the context is to be set
 *  \returns 0 in case of success; negative otherwise
 *
 * A logging context is something like the subscriber identity to which
 * the currently processed message relates, or the BTS through which it
 * was received.  As soon as this data is known, it can be set using
 * this function.  The main use of context information is for logging
 * filters.
 */
int log_set_context(uint8_t ctx_nr, void *value)
{
	if (ctx_nr > LOG_MAX_CTX)
		return -EINVAL;

	log_context.ctx[ctx_nr] = value;

	return 0;
}

/*! Enable the \ref LOG_FLT_ALL log filter
 *  \param[in] target Log target to be affected
 *  \param[in] all enable (1) or disable (0) the ALL filter
 *
 * When the \ref LOG_FLT_ALL filter is enabled, all log messages will be
 * printed.  It acts as a wildcard.  Setting it to \a 1 means there is no
 * filtering.
 */
void log_set_all_filter(struct log_target *target, int all)
{
	if (all)
		target->filter_map |= (1 << LOG_FLT_ALL);
	else
		target->filter_map &= ~(1 << LOG_FLT_ALL);
}

/*! Enable or disable the use of colored output
 *  \param[in] target Log target to be affected
 *  \param[in] use_color Use color (1) or don't use color (0)
 */
void log_set_use_color(struct log_target *target, int use_color)
{
	target->use_color = use_color;
}

/*! Enable or disable printing of timestamps while logging
 *  \param[in] target Log target to be affected
 *  \param[in] print_timestamp Enable (1) or disable (0) timestamps
 */
void log_set_print_timestamp(struct log_target *target, int print_timestamp)
{
	target->print_timestamp = print_timestamp;
}

/*! Enable or disable printing of extended timestamps while logging
 *  \param[in] target Log target to be affected
 *  \param[in] print_timestamp Enable (1) or disable (0) timestamps
 *
 * When both timestamp and extended timestamp is enabled then only
 * the extended timestamp will be used. The format of the timestamp
 * is YYYYMMDDhhmmssnnn.
 */
void log_set_print_extended_timestamp(struct log_target *target, int print_timestamp)
{
	target->print_ext_timestamp = print_timestamp;
}

/*! Use log_set_print_filename2() instead.
 * Call log_set_print_filename2() with LOG_FILENAME_PATH or LOG_FILENAME_NONE, *as well as* call
 * log_set_print_category_hex() with the argument passed to this function. This is to mirror legacy
 * behavior, which combined the category in hex with the filename. For example, if the category-hex
 * output were no longer affected by log_set_print_filename(), many unit tests (in libosmocore as well as
 * dependent projects) would fail since they expect the category to disappear along with the filename.
 *  \param[in] target Log target to be affected
 *  \param[in] print_filename Enable (1) or disable (0) filenames
 */
void log_set_print_filename(struct log_target *target, int print_filename)
{
	log_set_print_filename2(target, print_filename ? LOG_FILENAME_PATH : LOG_FILENAME_NONE);
	log_set_print_category_hex(target, print_filename);
}

/*! Enable or disable printing of the filename while logging.
 *  \param[in] target Log target to be affected.
 *  \param[in] print_filename An LOG_FILENAME_* enum value.
 * LOG_FILENAME_NONE omits the source file and line information from logs.
 * LOG_FILENAME_PATH prints the entire source file path as passed to LOGP macros.
 */
void log_set_print_filename2(struct log_target *target, enum log_filename_type lft)
{
	target->print_filename2 = lft;
}

/*! Enable or disable printing of the category name
 *  \param[in] target Log target to be affected
 *  \param[in] print_catname Enable (1) or disable (0) filenames
 *
 *  Print the category/subsys name in front of every log message.
 */
void log_set_print_category(struct log_target *target, int print_category)
{
	target->print_category = print_category;
}

/*! Enable or disable printing of the category number in hex ('<000b>').
 *  \param[in] target Log target to be affected.
 *  \param[in] print_category_hex Enable (1) or disable (0) hex category.
 */
void log_set_print_category_hex(struct log_target *target, int print_category_hex)
{
	target->print_category_hex = print_category_hex;
}

/*! Enable or disable printing of the log level name.
 *  \param[in] target Log target to be affected
 *  \param[in] print_catname Enable (1) or disable (0) filenames
 *
 *  Print the log level name in front of every log message.
 */
void log_set_print_level(struct log_target *target, int print_level)
{
	target->print_level = (bool)print_level;
}

/*! Set the global log level for a given log target
 *  \param[in] target Log target to be affected
 *  \param[in] log_level New global log level
 */
void log_set_log_level(struct log_target *target, int log_level)
{
	target->loglevel = log_level;
}

/*! Set a category filter on a given log target
 *  \param[in] target Log target to be affected
 *  \param[in] category Log category to be affected
 *  \param[in] enable whether to enable or disable the filter
 *  \param[in] level Log level of the filter
 */
void log_set_category_filter(struct log_target *target, int category,
			       int enable, int level)
{
	if (!target)
		return;
	category = map_subsys(category);
	target->categories[category].enabled = !!enable;
	target->categories[category].loglevel = level;
}

#if (!EMBEDDED)
static void _file_output(struct log_target *target, unsigned int level,
			 const char *log)
{
	fprintf(target->tgt_file.out, "%s", log);
	fflush(target->tgt_file.out);
}
#endif

/*! Create a new log target skeleton
 *  \returns dynamically-allocated log target
 *  This funcition allocates a \ref log_target and initializes it
 *  with some default values.  The newly created target is not
 *  registered yet.
 */
struct log_target *log_target_create(void)
{
	struct log_target *target;
	unsigned int i;

	assert_loginfo(__func__);

	target = talloc_zero(tall_log_ctx, struct log_target);
	if (!target)
		return NULL;

	target->categories = talloc_zero_array(target, 
						struct log_category,
						osmo_log_info->num_cat);
	if (!target->categories) {
		talloc_free(target);
		return NULL;
	}

	INIT_LLIST_HEAD(&target->entry);

	/* initialize the per-category enabled/loglevel from defaults */
	for (i = 0; i < osmo_log_info->num_cat; i++) {
		struct log_category *cat = &target->categories[i];
		cat->enabled = osmo_log_info->cat[i].enabled;
		cat->loglevel = osmo_log_info->cat[i].loglevel;
	}

	/* global settings */
	target->use_color = 1;
	target->print_timestamp = 0;
	target->print_filename2 = LOG_FILENAME_PATH;
	target->print_category_hex = true;

	/* global log level */
	target->loglevel = 0;
	return target;
}

/*! Create the STDERR log target
 *  \returns dynamically-allocated \ref log_target for STDERR */
struct log_target *log_target_create_stderr(void)
{
/* since C89/C99 says stderr is a macro, we can safely do this! */
#if !EMBEDDED && defined(stderr)
	struct log_target *target;

	target = log_target_create();
	if (!target)
		return NULL;

	target->type = LOG_TGT_TYPE_STDERR;
	target->tgt_file.out = stderr;
	target->output = _file_output;
	return target;
#else
	return NULL;
#endif /* stderr */
}

#if (!EMBEDDED)
/*! Create a new file-based log target
 *  \param[in] fname File name of the new log file
 *  \returns Log target in case of success, NULL otherwise
 */
struct log_target *log_target_create_file(const char *fname)
{
	struct log_target *target;

	target = log_target_create();
	if (!target)
		return NULL;

	target->type = LOG_TGT_TYPE_FILE;
	target->tgt_file.out = fopen(