diff --git a/examples/log.v b/examples/log.v
index e6426603ed..d2635577f6 100644
--- a/examples/log.v
+++ b/examples/log.v
@@ -1,6 +1,14 @@
 import log
 
 fn main() {
+	// Note: you *do not* need to create a logger instance, and pass it around, just to use the `log` module.
+	// The log module already creates an instance of a thread safe Logger, and utility functions to work with it:
+	log.set_level(.debug)
+	log.debug('simple debug message')
+	log.warn('simple warning message')
+	log.info('simple information message')
+	log.error('simple error message')
+
 	mut l := log.Log{}
 	l.set_level(.info)
 	// Make a new file called info.log in the current folder
diff --git a/vlib/log/README.md b/vlib/log/README.md
index 2c278b14d0..fdb643c47f 100644
--- a/vlib/log/README.md
+++ b/vlib/log/README.md
@@ -3,3 +3,48 @@
 `log` provides your application logging services.
 You can log to file or to the console and use different
 logging levels, so that you are not overwhelmed by the logs.
+
+## Basic usage:
+The log module creates a default Log instance by default, and
+provides utility functions, that you can use to access it.
+Note: the default Log instance is thread safe.
+
+That makes it very convenient to use in subsystems, without having
+to thread a log instance everywhere:
+```v
+import log
+
+fn abc() {
+	log.info('some information')
+	log.warn('a warning')
+}
+
+// this will not be visible, the default log level is .info:
+log.debug('a debug message')
+
+log.set_level(.debug)
+
+// this will be now visible, the log level was changed to .debug:
+log.debug('a debug message')
+
+abc()
+```
+
+## Advanced usage:
+You can also create your own log instances, with different options
+applied to them:
+```v
+import log
+
+fn main() {
+	mut l := log.Log{}
+	l.set_level(.info)
+	l.set_full_logpath('./info.log')
+	l.log_to_console_too()
+
+	l.info('info')
+	l.warn('warn')
+	l.error('error')
+	l.fatal('fatal') // panic, marked as [noreturn]
+}
+```
diff --git a/vlib/log/common.v b/vlib/log/common.v
new file mode 100644
index 0000000000..6349affb9c
--- /dev/null
+++ b/vlib/log/common.v
@@ -0,0 +1,69 @@
+module log
+
+import term
+
+// Level defines the possible log levels, used by Log.set_level()
+pub enum Level {
+	disabled = 0 // lowest level, disables everything else
+	fatal // disables error, warn, info and debug
+	error // disables warn, info and debug
+	warn // disables info and debug
+	info // disables debug
+	debug
+}
+
+// LogTarget defines the possible log targets, that Log supports
+pub enum LogTarget {
+	console
+	file
+	both
+}
+
+// tag_to_cli returns the tag for log level `l` as a colored string.
+fn tag_to_cli(l Level) string {
+	return match l {
+		.disabled { '' }
+		.fatal { term.red('FATAL') }
+		.error { term.red('ERROR') }
+		.warn { term.yellow('WARN ') }
+		.info { term.white('INFO ') }
+		.debug { term.magenta('DEBUG') }
+	}
+}
+
+// tag_to_file returns the tag for log level `l` as a string.
+fn tag_to_file(l Level) string {
+	return match l {
+		.disabled { '     ' }
+		.fatal { 'FATAL' }
+		.error { 'ERROR' }
+		.warn { 'WARN ' }
+		.info { 'INFO ' }
+		.debug { 'DEBUG' }
+	}
+}
+
+// level_from_tag returns the log level from the given string.
+// It returns `none` when it does not find a match.
+pub fn level_from_tag(tag string) ?Level {
+	return match tag {
+		'DISABLED' { Level.disabled }
+		'FATAL' { Level.fatal }
+		'ERROR' { Level.error }
+		'WARN' { Level.warn }
+		'INFO' { Level.info }
+		'DEBUG' { Level.debug }
+		else { none }
+	}
+}
+
+// target_from_label returns the log target from the given string.
+// It returns `none` when it does not find a match.
+pub fn target_from_label(label string) ?LogTarget {
+	return match label {
+		'console' { LogTarget.console }
+		'file' { LogTarget.file }
+		'both' { LogTarget.both }
+		else { none }
+	}
+}
diff --git a/vlib/log/default.c.v b/vlib/log/default.c.v
new file mode 100644
index 0000000000..d265bdd93c
--- /dev/null
+++ b/vlib/log/default.c.v
@@ -0,0 +1,42 @@
+// Copyright (c) 2019-2023 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+[has_globals]
+module log
+
+__global default_logger &Logger
+
+// TODO: remove this hack, when the language has a way to access the raw pointer to an interface value directly:
+[typedef]
+struct C.log__Logger {
+mut:
+	_object voidptr
+}
+
+// init will be called before the user's main program starts, to initialize the default logger
+fn init() {
+	default_logger = new_thread_safe_log()
+	C.atexit(deinit)
+}
+
+// deinit will be called on exit of the program and will free the memory allocated for the default logger
+fn deinit() {
+	free_logger(default_logger)
+}
+
+[manualfree]
+fn free_logger(logger &Logger) {
+	if voidptr(logger) == unsafe { nil } {
+		return
+	}
+	unsafe {
+		// C.printf(c'free_logger logger: %p\n', logger)
+		logger.free()
+		//
+		pobject := &C.log__Logger(logger)._object
+		// C.printf(c'free_logger pobject: %p\n', pobject)
+		free(pobject)
+		//
+		free(logger)
+	}
+}
diff --git a/vlib/log/default.v b/vlib/log/default.v
new file mode 100644
index 0000000000..ee25d86d9f
--- /dev/null
+++ b/vlib/log/default.v
@@ -0,0 +1,55 @@
+// Copyright (c) 2019-2023 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+module log
+
+// set_logger changes the default logger instance to the one provided by the user.
+// The existing logger will be freed, *after* the change is done.
+[manualfree]
+pub fn set_logger(logger &Logger) {
+	// C.printf(c"set_logger  logger: %p | old logger: %p\n", logger, default_logger)
+	old_logger := unsafe { default_logger }
+	default_logger = unsafe { logger }
+	free_logger(old_logger)
+}
+
+// get_logger returns a pointer to the current default logger instance
+[unsafe]
+pub fn get_logger() &Logger {
+	return default_logger
+}
+
+// get_level returns the log level of the default Logger instance
+pub fn get_level() Level {
+	return default_logger.get_level()
+}
+
+// set_level changes the log level of the default Logger instance
+pub fn set_level(level Level) {
+	default_logger.set_level(level)
+}
+
+// fatal logs a `fatal` message, using the default Logger instance
+pub fn fatal(s string) {
+	default_logger.fatal(s)
+}
+
+// error logs an `error` message, using the default Logger instance
+pub fn error(s string) {
+	default_logger.error(s)
+}
+
+// error logs a `warning` message, using the default Logger instance
+pub fn warn(s string) {
+	default_logger.warn(s)
+}
+
+// info logs an `info` message, using the default Logger instance
+pub fn info(s string) {
+	default_logger.info(s)
+}
+
+// debug logs a `debug` message, using the default Logger instance
+pub fn debug(s string) {
+	default_logger.debug(s)
+}
diff --git a/vlib/log/default_test.v b/vlib/log/default_test.v
new file mode 100644
index 0000000000..d6b1076fb0
--- /dev/null
+++ b/vlib/log/default_test.v
@@ -0,0 +1,37 @@
+import log
+import time
+
+fn test_default_log_instance() {
+	println(@FN + ' start')
+	log.info('info')
+	log.warn('warn')
+	log.error('error')
+	log.debug('no output for debug')
+	println('^^^ there should be no `no output for debug` shown above')
+	log.set_level(.debug)
+	log.debug('debug now')
+	println('^^^ there should be `debug now` shown above')
+	log.set_level(log.level_from_tag('INFO') or { log.Level.disabled })
+	log.info('info again')
+	log.set_level(log.level_from_tag('') or { log.Level.disabled })
+	log.error('no output anymore')
+	println('^^^ there should be no `no output anymore` shown above')
+	println(@FN + ' end')
+}
+
+fn log_messages(tidx int) {
+	time.sleep(2 * time.millisecond)
+	for i in 0 .. 3 {
+		log.debug('hi from thread ${tidx}')
+	}
+}
+
+fn test_default_log_instance_used_in_multiple_threads() {
+	eprintln('\n${@METHOD} start')
+	log.set_level(.debug)
+	mut threads := []thread{}
+	for tidx in 0 .. 3 {
+		threads << spawn log_messages(tidx)
+	}
+	threads.wait()
+}
diff --git a/vlib/log/log.v b/vlib/log/log.v
index 8ff87f2d88..179617777c 100644
--- a/vlib/log/log.v
+++ b/vlib/log/log.v
@@ -5,82 +5,6 @@ module log
 
 import os
 import time
-import term
-
-// Level defines possible log levels used by `Log`
-pub enum Level {
-	disabled = 0
-	fatal
-	error
-	warn
-	info
-	debug
-}
-
-// LogTarget defines possible log targets
-pub enum LogTarget {
-	console
-	file
-	both
-}
-
-// tag_to_cli returns the tag for log level `l` as a colored string.
-fn tag_to_cli(l Level) string {
-	return match l {
-		.disabled { '' }
-		.fatal { term.red('FATAL') }
-		.error { term.red('ERROR') }
-		.warn { term.yellow('WARN ') }
-		.info { term.white('INFO ') }
-		.debug { term.blue('DEBUG') }
-	}
-}
-
-// tag_to_file returns the tag for log level `l` as a string.
-fn tag_to_file(l Level) string {
-	return match l {
-		.disabled { '     ' }
-		.fatal { 'FATAL' }
-		.error { 'ERROR' }
-		.warn { 'WARN ' }
-		.info { 'INFO ' }
-		.debug { 'DEBUG' }
-	}
-}
-
-// level_from_tag returns the log level from the given string if it matches.
-pub fn level_from_tag(tag string) ?Level {
-	return match tag {
-		'DISABLED' { Level.disabled }
-		'FATAL' { Level.fatal }
-		'ERROR' { Level.error }
-		'WARN' { Level.warn }
-		'INFO' { Level.info }
-		'DEBUG' { Level.debug }
-		else { none }
-	}
-}
-
-// target_from_label returns the log target from the given string if it matches.
-pub fn target_from_label(label string) ?LogTarget {
-	return match label {
-		'console' { LogTarget.console }
-		'file' { LogTarget.file }
-		'both' { LogTarget.both }
-		else { none }
-	}
-}
-
-// Logger is an interface that describes a generic Logger
-pub interface Logger {
-mut:
-	fatal(s string)
-	error(s string)
-	warn(s string)
-	info(s string)
-	debug(s string)
-	set_level(level Level)
-}
 
 // Log represents a logging object
 pub struct Log {
@@ -94,16 +18,20 @@ pub mut:
 }
 
 // get_level gets the internal logging level.
-pub fn (mut l Log) get_level() Level {
+pub fn (l &Log) get_level() Level {
 	return l.level
 }
 
-// set_level sets the internal logging to `level`.
+// set_level sets the logging level to `level`. Messges for levels above it will skipped.
+// For example, after calling log.set_level(.info), log.debug('message') will produce nothing.
+// Call log.set_level(.disabled) to turn off the logging of all messages.
 pub fn (mut l Log) set_level(level Level) {
 	l.level = level
 }
 
 // set_output_level sets the internal logging output to `level`.
+[deprecated: 'use .set_level(level) instead']
+[deprecated_after: '2023-09-30']
 pub fn (mut l Log) set_output_level(level Level) {
 	l.level = level
 }
@@ -154,14 +82,14 @@ pub fn (mut l Log) close() {
 
 // log_file writes log line `s` with `level` to the log file.
 fn (mut l Log) log_file(s string, level Level) {
-	timestamp := time.now().format_ss()
+	timestamp := time.now().format_ss_micro()
 	e := tag_to_file(level)
 	l.ofile.writeln('${timestamp} [${e}] ${s}') or { panic(err) }
 }
 
 // log_cli writes log line `s` with `level` to stdout.
 fn (l &Log) log_cli(s string, level Level) {
-	timestamp := time.now().format_ss()
+	timestamp := time.now().format_ss_micro()
 	e := tag_to_cli(level)
 	println('${timestamp} [${e}] ${s}')
 }
@@ -219,3 +147,13 @@ pub fn (mut l Log) debug(s string) {
 	}
 	l.send_output(s, .debug)
 }
+
+// free frees the given Log instance
+[unsafe]
+pub fn (mut f Log) free() {
+	unsafe {
+		f.output_label.free()
+		f.ofile.close()
+		f.output_file_name.free()
+	}
+}
diff --git a/vlib/log/log_test.v b/vlib/log/log_test.v
index e6c1a7337b..576ed9ffb4 100644
--- a/vlib/log/log_test.v
+++ b/vlib/log/log_test.v
@@ -1,7 +1,5 @@
 module log
 
-import time
-
 fn log_mutable_statements(mut log Log) {
 	println(@FN + ' start')
 	log.info('info')
@@ -30,10 +28,6 @@ fn logger_mutable_statements(mut log Logger) {
 	println(@FN + ' end')
 }
 
-fn delay() {
-	time.sleep(1 * time.second)
-}
-
 // Note that Log and Logger methods requires a mutable instance
 
 // new_log create and return a new Log reference
@@ -63,8 +57,8 @@ fn test_log_mutable_reference() {
 	println(@FN + ' start')
 	mut log := new_log()
 	assert typeof(log).name == '&log.Log'
-	spawn log_mutable_statements(mut log)
-	delay() // wait to finish
+	t := spawn log_mutable_statements(mut log)
+	t.wait()
 	assert true
 	println(@FN + ' end')
 }
@@ -75,8 +69,8 @@ fn test_logger_mutable_reference() {
 	mut logger := new_log_as_logger()
 	logger.set_level(.warn)
 	assert typeof(logger).name == '&log.Logger'
-	spawn logger_mutable_statements(mut logger)
-	delay() // wait to finish
+	t := spawn logger_mutable_statements(mut logger)
+	t.wait()
 	assert true
 	println(@FN + ' end')
 }
diff --git a/vlib/log/logger_interface.v b/vlib/log/logger_interface.v
new file mode 100644
index 0000000000..d716a78ac2
--- /dev/null
+++ b/vlib/log/logger_interface.v
@@ -0,0 +1,15 @@
+module log
+
+// Logger is an interface that describes a generic Logger
+pub interface Logger {
+	get_level() Level
+mut:
+	fatal(s string)
+	error(s string)
+	warn(s string)
+	info(s string)
+	debug(s string)
+	// utility methods:
+	set_level(level Level)
+	free()
+}
diff --git a/vlib/log/safe_log.v b/vlib/log/safe_log.v
new file mode 100644
index 0000000000..8aaddf113d
--- /dev/null
+++ b/vlib/log/safe_log.v
@@ -0,0 +1,79 @@
+module log
+
+import sync
+
+// ThreadSafeLog embeds Log, and adds a mutex field.
+// It uses the mutex to synchronise accesses to the embedded Log.
+pub struct ThreadSafeLog {
+	Log
+pub mut:
+	mu sync.Mutex
+}
+
+// new_thread_safe_log returns a new log structure, whose methods are safe
+// to call by multiple threads.
+pub fn new_thread_safe_log() &ThreadSafeLog {
+	mut x := &ThreadSafeLog{
+		level: .info
+	}
+	x.mu.init()
+	return x
+}
+
+// free frees the given ThreadSafeLog instance.
+[unsafe]
+pub fn (mut x ThreadSafeLog) free() {
+	unsafe {
+		x.Log.free()
+		x.mu.destroy()
+		// C.printf(c'ThreadSafeLog free(x), x: %p\n', x)
+	}
+}
+
+// set_level changes the log level
+pub fn (mut x ThreadSafeLog) set_level(level Level) {
+	x.mu.@lock()
+	x.Log.set_level(level)
+	x.mu.unlock()
+}
+
+// debug logs a debug message
+pub fn (mut x ThreadSafeLog) debug(s string) {
+	x.mu.@lock()
+	x.Log.debug(s)
+	x.mu.unlock()
+}
+
+// info logs an info messagep
+pub fn (mut x ThreadSafeLog) info(s string) {
+	x.mu.@lock()
+	x.Log.info(s)
+	x.mu.unlock()
+}
+
+// warn logs a warning message
+pub fn (mut x ThreadSafeLog) warn(s string) {
+	x.mu.@lock()
+	x.Log.warn(s)
+	x.mu.unlock()
+}
+
+// error logs an error message
+pub fn (mut x ThreadSafeLog) error(s string) {
+	x.mu.@lock()
+	x.Log.error(s)
+	x.mu.unlock()
+}
+
+// fatal logs a fatal message, and panics
+[noreturn]
+pub fn (mut x ThreadSafeLog) fatal(s string) {
+	x.mu.@lock()
+	defer {
+		// TODO: Log.fatal() is marked as noreturn, but this defer is allowed.
+		// Think whether it should be, or if it should be a compiler notice at least,
+		// since it would not be reached at all (.fatal() panics).
+		x.mu.unlock()
+	}
+	x.Log.fatal(s)
+}
diff --git a/vlib/sync/common_mutex.v b/vlib/sync/common_mutex.v
new file mode 100644
index 0000000000..f2cf330ed7
--- /dev/null
+++ b/vlib/sync/common_mutex.v
@@ -0,0 +1,11 @@
+module sync
+
+// str returns a string representation of the Mutex pointer
+pub fn (m &Mutex) str() string {
+	return 'Mutex(${voidptr(m)})'
+}
+
+// str returns a string representation of the RwMutex pointer
+pub fn (m &RwMutex) str() string {
+	return 'RwMutex(${voidptr(m)})'
+}
diff --git a/vlib/sync/sync.c.v b/vlib/sync/sync.c.v
new file mode 100644
index 0000000000..99de1653c7
--- /dev/null
+++ b/vlib/sync/sync.c.v
@@ -0,0 +1,11 @@
+module sync
+
+[noreturn]
+fn cpanic(res int) {
+	panic(unsafe { tos_clone(&u8(C.strerror(res))) })
+}
+
+[noreturn]
+fn cpanic_errno() {
+	cpanic(C.errno)
+}
diff --git a/vlib/sync/sync_darwin.c.v b/vlib/sync/sync_darwin.c.v
index 8d58230de0..5fb497ca4f 100644
--- a/vlib/sync/sync_darwin.c.v
+++ b/vlib/sync/sync_darwin.c.v
@@ -21,6 +21,7 @@ fn C.pthread_rwlock_init(voidptr, voidptr) int
 fn C.pthread_rwlock_rdlock(voidptr) int
 fn C.pthread_rwlock_wrlock(voidptr) int
 fn C.pthread_rwlock_unlock(voidptr) int
+fn C.pthread_rwlock_destroy(voidptr) int
 fn C.pthread_condattr_init(voidptr) int
 fn C.pthread_condattr_setpshared(voidptr, int) int
 fn C.pthread_condattr_destroy(voidptr) int
@@ -76,22 +77,29 @@ mut:
 	count u32
 }
 
+// new_mutex creates and initialises a new mutex instance on the heap, then returns a pointer to it.
 pub fn new_mutex() &Mutex {
 	mut m := &Mutex{}
 	m.init()
 	return m
 }
 
+// init initialises the mutex. It should be called once before the mutex is used,
+// since it creates the associated resources needed for the mutex to work properly.
+[inline]
 pub fn (mut m Mutex) init() {
 	C.pthread_mutex_init(&m.mutex, C.NULL)
 }
 
+// new_rwmutex creates a new read/write mutex instance on the heap, and returns a pointer to it.
 pub fn new_rwmutex() &RwMutex {
 	mut m := &RwMutex{}
 	m.init()
 	return m
 }
 
+// init initialises the RwMutex instance. It should be called once before the rw mutex is used,
+// since it creates the associated resources needed for the mutex to work properly.
 pub fn (mut m RwMutex) init() {
 	a := RwMutexAttr{}
 	C.pthread_rwlockattr_init(&a.attr)
@@ -101,45 +109,100 @@ pub fn (mut m RwMutex) init() {
 	C.pthread_rwlock_init(&m.mutex, &a.attr)
 }
 
-// @lock(), for *manual* mutex handling, since `lock` is a keyword
+// @lock locks the mutex instance (`lock` is a keyword).
+// If the mutex was already locked, it will block, till it is unlocked.
+[inline]
 pub fn (mut m Mutex) @lock() {
 	C.pthread_mutex_lock(&m.mutex)
 }
 
+// unlock unlocks the mutex instance. The mutex is released, and one of
+// the other threads, that were blocked, because they called @lock can continue.
+[inline]
 pub fn (mut m Mutex) unlock() {
 	C.pthread_mutex_unlock(&m.mutex)
 }
 
-// RwMutex has separate read- and write locks
+// destroy frees the resources associated with the mutex instance.
+// Note: the mutex itself is not freed.
+[inline]
+pub fn (mut m Mutex) destroy() {
+	res := C.pthread_mutex_destroy(&m.mutex)
+	if res != 0 {
+		cpanic(res)
+	}
+}
+
+// @rlock locks the given RwMutex instance for reading.
+// If the mutex was already locked, it will block, and will try to get the lock,
+// once the lock is released by another thread calling unlock.
+// Once it succeds, it returns.
+// Note: there may be several threads that are waiting for the same lock.
+// Note: RwMutex has separate read and write locks.
+[inline]
 pub fn (mut m RwMutex) @rlock() {
 	C.pthread_rwlock_rdlock(&m.mutex)
 }
 
+// @lock locks the given RwMutex instance for writing.
+// If the mutex was already locked, it will block, till it is unlocked,
+// then it will try to get the lock, and if it can, it will return, otherwise
+// it will continue waiting for the mutex to become unlocked.
+// Note: there may be several threads that are waiting for the same lock.
+// Note: RwMutex has separate read and write locks.
+[inline]
 pub fn (mut m RwMutex) @lock() {
 	C.pthread_rwlock_wrlock(&m.mutex)
 }
 
-// Windows SRWLocks have different function to unlock
-// So provide two functions here, too, to have a common interface
+// destroy frees the resources associated with the rwmutex instance.
+// Note: the mutex itself is not freed.
+[inline]
+pub fn (mut m RwMutex) destroy() {
+	res := C.pthread_rwlock_destroy(&m.mutex)
+	if res != 0 {
+		cpanic(res)
+	}
+}
+
+// runlock unlocks the RwMutex instance, locked for reading.
+// Note: Windows SRWLocks have different function to unlocking.
+// To have a common portable API, there are two methods for
+// unlocking here as well, even though that they do the same
+// on !windows platforms.
+[inline]
 pub fn (mut m RwMutex) runlock() {
 	C.pthread_rwlock_unlock(&m.mutex)
 }
 
+// unlock unlocks the RwMutex instance, locked for writing.
+// Note: Windows SRWLocks have different function to unlocking.
+// To have a common portable API, there are two methods for
+// unlocking here as well, even though that they do the same
+// on !windows platforms.
+[inline]
 pub fn (mut m RwMutex) unlock() {
 	C.pthread_rwlock_unlock(&m.mutex)
 }
 
+// new_semaphore creates a new initialised Semaphore instance on the heap, and returns a pointer to it.
+// The initial counter value of the semaphore is 0.
 [inline]
 pub fn new_semaphore() &Semaphore {
 	return new_semaphore_init(0)
 }
 
+// new_semaphore_init creates a new initialised Semaphore instance on the heap, and returns a pointer to it.
+// The `n` parameter can be used to set the initial counter value of the semaphore.
 pub fn new_semaphore_init(n u32) &Semaphore {
 	mut sem := &Semaphore{}
 	sem.init(n)
 	return sem
 }
 
+// init initialises the Semaphore instance with `n` as its initial counter value.
+// It should be called once before the semaphore is used, since it creates the associated
+// resources needed for the semaphore to work properly.
 pub fn (mut sem Semaphore) init(n u32) {
 	C.atomic_store_u32(&sem.count, n)
 	C.pthread_mutex_init(&sem.mtx, C.NULL)
@@ -150,6 +213,10 @@ pub fn (mut sem Semaphore) init(n u32) {
 	C.pthread_condattr_destroy(&attr.attr)
 }
 
+// post increases the counter of the semaphore by 1.
+// If the resulting counter value is > 0, and if there is a thread waiting
+// on the semaphore, the waiting thread will decrement the counter by 1, and
+// then will continue running. See also .wait() .
 pub fn (mut sem Semaphore) post() {
 	mut c := C.atomic_load_u32(&sem.count)
 	for c > 1 {
@@ -157,6 +224,7 @@ pub fn (mut sem Semaphore) post() {
 			return
 		}
 	}
+
 	C.pthread_mutex_lock(&sem.mtx)
 	c = C.atomic_fetch_add_u32(&sem.count, 1)
 	if c == 0 {
@@ -165,6 +233,11 @@ pub fn (mut sem Semaphore) post() {
 	C.pthread_mutex_unlock(&sem.mtx)
 }
 
+// wait will just decrement the semaphore count, if it was positive.
+// It it was not positive, it will waits for the semaphore count to reach a positive number.
+// When that happens, it will decrease the semaphore count, and will return.
+// In effect, it allows you to block threads, until the semaphore, is posted by another thread.
+// See also .post() .
 pub fn (mut sem Semaphore) wait() {
 	mut c := C.atomic_load_u32(&sem.count)
 	for c > 0 {
@@ -172,9 +245,9 @@ pub fn (mut sem Semaphore) wait() {
 			return
 		}
 	}
+
 	C.pthread_mutex_lock(&sem.mtx)
 	c = C.atomic_load_u32(&sem.count)
-
 	outer: for {
 		if c == 0 {
 			C.pthread_cond_wait(&sem.cond, &sem.mtx)
@@ -192,6 +265,10 @@ pub fn (mut sem Semaphore) wait() {
 	C.pthread_mutex_unlock(&sem.mtx)
 }
 
+// try_wait tries to decrease the semaphore count by 1, if it was positive.
+// If it succeeds in that, it returns true, otherwise it returns false.
+// Note: try_wait should return as fast as possible so error handling is only
+// done when debugging
 pub fn (mut sem Semaphore) try_wait() bool {
 	mut c := C.atomic_load_u32(&sem.count)
 	for c > 0 {
@@ -202,6 +279,8 @@ pub fn (mut sem Semaphore) try_wait() bool {
 	return false
 }
 
+// timed_wait is similar to .wait(), but it also accepts a timeout duration,
+// thus it can return false early, if the timeout passed before the semaphore was posted.
 pub fn (mut sem Semaphore) timed_wait(timeout time.Duration) bool {
 	mut c := C.atomic_load_u32(&sem.count)
 	for c > 0 {
@@ -235,13 +314,15 @@ pub fn (mut sem Semaphore) timed_wait(timeout time.Duration) bool {
 	return res == 0
 }
 
+// destroy frees the resources associated with the Semaphore instance.
+// Note: the semaphore instance itself is not freed.
 pub fn (mut sem Semaphore) destroy() {
 	mut res := C.pthread_cond_destroy(&sem.cond)
-	if res == 0 {
-		res = C.pthread_mutex_destroy(&sem.mtx)
-		if res == 0 {
-			return
-		}
+	if res != 0 {
+		cpanic(res)
+	}
+	res = C.pthread_mutex_destroy(&sem.mtx)
+	if res != 0 {
+		cpanic(res)
 	}
-	panic(unsafe { tos_clone(&u8(C.strerror(res))) })
 }
diff --git a/vlib/sync/sync_default.c.v b/vlib/sync/sync_default.c.v
index be15deada9..43dde304df 100644
--- a/vlib/sync/sync_default.c.v
+++ b/vlib/sync/sync_default.c.v
@@ -66,26 +66,29 @@ pub struct Semaphore {
 	sem C.sem_t
 }
 
-// new_mutex create and init a new mutex object. You should not call `init` again.
+// new_mutex creates and initialises a new mutex instance on the heap, then returns a pointer to it.
 pub fn new_mutex() &Mutex {
 	mut m := &Mutex{}
 	m.init()
 	return m
 }
 
-// init the mutex object.
+// init initialises the mutex. It should be called once before the mutex is used,
+// since it creates the associated resources needed for the mutex to work properly.
+[inline]
 pub fn (mut m Mutex) init() {
 	C.pthread_mutex_init(&m.mutex, C.NULL)
 }
 
-// new_rwmutex create and init a new rwmutex object. You should not call `init` again.
+// new_rwmutex creates a new read/write mutex instance on the heap, and returns a pointer to it.
 pub fn new_rwmutex() &RwMutex {
 	mut m := &RwMutex{}
 	m.init()
 	return m
 }
 
-// init the rwmutex object.
+// init initialises the RwMutex instance. It should be called once before the rw mutex is used,
+// since it creates the associated resources needed for the mutex to work properly.
 pub fn (mut m RwMutex) init() {
 	a := RwMutexAttr{}
 	C.pthread_rwlockattr_init(&a.attr)
@@ -96,79 +99,117 @@ pub fn (mut m RwMutex) init() {
 	C.pthread_rwlockattr_destroy(&a.attr) // destroy the attr when done
 }
 
-// @lock the mutex, wait and return after got the mutex lock.
+// @lock locks the mutex instance (`lock` is a keyword).
+// If the mutex was already locked, it will block, till it is unlocked.
+[inline]
 pub fn (mut m Mutex) @lock() {
 	C.pthread_mutex_lock(&m.mutex)
 }
 
-// unlock the mutex. The mutex is released.
+// unlock unlocks the mutex instance. The mutex is released, and one of
+// the other threads, that were blocked, because they called @lock can continue.
+[inline]
 pub fn (mut m Mutex) unlock() {
 	C.pthread_mutex_unlock(&m.mutex)
 }
 
-// destroy the mutex object.
+// destroy frees the resources associated with the mutex instance.
+// Note: the mutex itself is not freed.
 pub fn (mut m Mutex) destroy() {
 	res := C.pthread_mutex_destroy(&m.mutex)
-	if res == 0 {
-		return
+	if res != 0 {
+		cpanic(res)
 	}
-	panic(unsafe { tos_clone(&u8(C.strerror(res))) })
 }
 
-// @rlock read-lock the rwmutex, wait and return after got read access.
+// @rlock locks the given RwMutex instance for reading.
+// If the mutex was already locked, it will block, and will try to get the lock,
+// once the lock is released by another thread calling unlock.
+// Once it succeds, it returns.
+// Note: there may be several threads that are waiting for the same lock.
+// Note: RwMutex has separate read and write locks.
+[inline]
 pub fn (mut m RwMutex) @rlock() {
 	C.pthread_rwlock_rdlock(&m.mutex)
 }
 
-// @lock read & write-lock the rwmutex, wait and return after got read & write access.
+// @lock locks the given RwMutex instance for writing.
+// If the mutex was already locked, it will block, till it is unlocked,
+// then it will try to get the lock, and if it can, it will return, otherwise
+// it will continue waiting for the mutex to become unlocked.
+// Note: there may be several threads that are waiting for the same lock.
+// Note: RwMutex has separate read and write locks.
+[inline]
 pub fn (mut m RwMutex) @lock() {
 	C.pthread_rwlock_wrlock(&m.mutex)
 }
 
-// destroy the rwmutex object.
+// destroy frees the resources associated with the rwmutex instance.
+// Note: the mutex itself is not freed.
 pub fn (mut m RwMutex) destroy() {
 	res := C.pthread_rwlock_destroy(&m.mutex)
-	if res == 0 {
-		return
+	if res != 0 {
+		cpanic(res)
 	}
-	panic(unsafe { tos_clone(&u8(C.strerror(res))) })
 }
 
-// Windows SRWLocks have different function to unlock
-// So provide two functions here, too, to have a common interface
+// runlock unlocks the RwMutex instance, locked for reading.
+// Note: Windows SRWLocks have different function to unlocking.
+// To have a common portable API, there are two methods for
+// unlocking here as well, even though that they do the same
+// on !windows platforms.
+[inline]
 pub fn (mut m RwMutex) runlock() {
 	C.pthread_rwlock_unlock(&m.mutex)
 }
 
-// unlock the rwmutex object. The rwmutex is released.
+// unlock unlocks the RwMutex instance, locked for writing.
+// Note: Windows SRWLocks have different function to unlocking.
+// To have a common portable API, there are two methods for
+// unlocking here as well, even though that they do the same
+// on !windows platforms.
+[inline]
 pub fn (mut m RwMutex) unlock() {
 	C.pthread_rwlock_unlock(&m.mutex)
 }
 
-// new_semaphore create a new semaphore, with zero initial value.
+// new_semaphore creates a new initialised Semaphore instance on the heap, and returns a pointer to it.
+// The initial counter value of the semaphore is 0.
 [inline]
 pub fn new_semaphore() &Semaphore {
 	return new_semaphore_init(0)
 }
 
-// new_semaphore_init create a semaphore, with `n` initial value.
+// new_semaphore_init creates a new initialised Semaphore instance on the heap, and returns a pointer to it.
+// The `n` parameter can be used to set the initial counter value of the semaphore.
 pub fn new_semaphore_init(n u32) &Semaphore {
 	mut sem := &Semaphore{}
 	sem.init(n)
 	return sem
 }
 
-// init the semaphore, with `n` initial value.
+// init initialises the Semaphore instance with `n` as its initial counter value.
+// It should be called once before the semaphore is used, since it creates the associated
+// resources needed for the semaphore to work properly.
+[inline]
 pub fn (mut sem Semaphore) init(n u32) {
 	C.sem_init(&sem.sem, 0, n)
 }
 
-// post increase the semaphore's value by 1.
+// post increases/unlocks the counter of the semaphore by 1.
+// If the resulting counter value is > 0, and if there is another thread waiting
+// on the semaphore, the waiting thread will decrement the counter by 1
+// (locking the semaphore), and then will continue running. See also .wait() .
+[inline]
 pub fn (mut sem Semaphore) post() {
 	C.sem_post(&sem.sem)
 }
 
-// wait decrease the semaphore's value by 1. If semaphore's original value is zero, then wait.
+// wait will just decrement the semaphore count, if it was positive.
+// It it was not positive, it will waits for the semaphore count to reach a positive number.
+// When that happens, it will decrease the semaphore count (lock the semaphore), and will return.
+// In effect, it allows you to block threads, until the semaphore, is posted by another thread.
+// See also .post() .
 pub fn (mut sem Semaphore) wait() {
 	for {
 		if C.sem_wait(&sem.sem) == 0 {
@@ -180,12 +221,14 @@ pub fn (mut sem Semaphore) wait() {
 				continue // interrupted by signal
 			}
 			else {
-				panic(unsafe { tos_clone(&u8(C.strerror(C.errno))) })
+				cpanic_errno()
 			}
 		}
 	}
 }
 
+// try_wait tries to decrease the semaphore count by 1, if it was positive.
+// If it succeeds in that, it returns true, otherwise it returns false.
 // try_wait should return as fast as possible so error handling is only
 // done when debugging
 pub fn (mut sem Semaphore) try_wait() bool {
@@ -199,7 +242,7 @@ pub fn (mut sem Semaphore) try_wait() bool {
 					return false
 				}
 				else {
-					panic(unsafe { tos_clone(&u8(C.strerror(C.errno))) })
+					cpanic_errno()
 				}
 			}
 		}
@@ -207,8 +250,8 @@ pub fn (mut sem Semaphore) try_wait() bool {
 	}
 }
 
-// timed_wait decrease the semaphore's value by 1. If semaphore's original
-// value is zero, then wait. If `timeout` return false.
+// timed_wait is similar to .wait(), but it also accepts a timeout duration,
+// thus it can return false early, if the timeout passed before the semaphore was posted.
 pub fn (mut sem Semaphore) timed_wait(timeout time.Duration) bool {
 	$if macos {
 		time.sleep(timeout)
@@ -230,18 +273,18 @@ pub fn (mut sem Semaphore) timed_wait(timeout time.Duration) bool {
 				break
 			}
 			else {
-				panic(unsafe { tos_clone(&u8(C.strerror(e))) })
+				cpanic(e)
 			}
 		}
 	}
 	return false
 }
 
-// destroy the semaphore object.
+// destroy frees the resources associated with the Semaphore instance.
+// Note: the semaphore instance itself is not freed.
 pub fn (mut sem Semaphore) destroy() {
 	res := C.sem_destroy(&sem.sem)
-	if res == 0 {
-		return
+	if res != 0 {
+		cpanic(res)
 	}
-	panic(unsafe { tos_clone(&u8(C.strerror(res))) })
 }
diff --git a/vlib/sync/sync_windows.c.v b/vlib/sync/sync_windows.c.v
index 6ec84fbbc2..a93145db35 100644
--- a/vlib/sync/sync_windows.c.v
+++ b/vlib/sync/sync_windows.c.v
@@ -92,10 +92,6 @@ pub fn (mut m RwMutex) unlock() {
 	C.ReleaseSRWLockExclusive(&m.mx)
 }
 
-pub fn (mut m Mutex) destroy() {
-	// nothing to do
-}
-
 [inline]
 pub fn new_semaphore() &Semaphore {
 	return new_semaphore_init(0)
@@ -208,5 +204,14 @@ pub fn (mut sem Semaphore) timed_wait(timeout time.Duration) bool {
 	return res != 0
 }
 
-pub fn (s Semaphore) destroy() {
+pub fn (mut m RwMutex) destroy() {
+	// nothing to do
+}
+
+pub fn (mut m Mutex) destroy() {
+	// nothing to do
+}
+
+pub fn (s Semaphore) destroy() {
+	// nothing to do
 }
diff --git a/vlib/v/tests/str_gen_test.v b/vlib/v/tests/str_gen_test.v
index 9730d1f1c3..6b0150e424 100644
--- a/vlib/v/tests/str_gen_test.v
+++ b/vlib/v/tests/str_gen_test.v
@@ -443,7 +443,6 @@ fn test_multi_return() {
 
 fn test_fixed_array_of_function() {
 	a := [println, println]!
-	println(a)
 	assert '${a}' == '[fn (string), fn (string)]'
 }
 
@@ -452,16 +451,10 @@ struct CTypeDefStruct {
 }
 
 fn test_c_struct_typedef() {
-	$if macos || linux {
-		c := CTypeDefStruct{
-			mutex: sync.new_mutex()
-		}
-		assert c.str() == r'CTypeDefStruct{
-    mutex: &sync.Mutex{
-        mutex: C.pthread_mutex_t{}
-    }
-}'
-	}
+	c := CTypeDefStruct{}
+	cstr := c.str()
+	assert cstr.starts_with('CTypeDefStruct')
+	assert cstr.contains('mutex: &Mutex(')
 }
 
 struct CharptrToStr {