diff --git a/vlib/flag/flag.v b/vlib/flag/flag.v
index a2cda98dfe..08329e4a85 100644
--- a/vlib/flag/flag.v
+++ b/vlib/flag/flag.v
@@ -10,6 +10,15 @@ pub:
 	// and also the default value, when the flag is not given
 }
 
+[unsafe]
+fn (mut f Flag) free() {
+	unsafe {
+		f.name.free()
+		f.usage.free()
+		f.val_desc.free()
+	}
+}
+
 pub fn (f Flag) str() string {
 	return '' + '    flag:\n' + '            name: $f.name\n' + '            abbr: $f.abbr\n' +
 		'            usag: $f.usage\n' + '            desc: $f.val_desc'
@@ -41,8 +50,16 @@ pub mut:
 [unsafe]
 fn (mut f FlagParser) free() {
 	unsafe {
+		for a in f.args {
+			a.free()
+		}
 		f.args.free()
+		//
+		for flag in f.flags {
+			flag.free()
+		}
 		f.flags.free()
+		//
 		f.application_name.free()
 		f.application_version.free()
 		f.application_description.free()
@@ -105,10 +122,17 @@ fn (mut fs FlagParser) add_flag(name string, abbr byte, usage string, desc strin
 //
 // - the name, usage are registered
 // - found arguments and corresponding values are removed from args list
+[manualfree]
 fn (mut fs FlagParser) parse_value(longhand string, shorthand byte) []string {
 	full := '--$longhand'
+	defer {
+		unsafe { full.free() }
+	}
 	mut found_entries := []string{}
 	mut to_delete := []int{}
+	defer {
+		unsafe { to_delete.free() }
+	}
 	mut should_skip_one := false
 	for i, arg in fs.args {
 		if should_skip_one {
@@ -127,10 +151,15 @@ fn (mut fs FlagParser) parse_value(longhand string, shorthand byte) []string {
 				return []
 			}
 			nextarg := fs.args[i + 1]
-			if nextarg.len > 2 && nextarg[..2] == '--' {
-				// It could be end of input (--) or another argument (--abc).
-				// Both are invalid so die.
-				return []
+			if nextarg.len > 2 {
+				nextarg_rest := nextarg[..2]
+				if nextarg_rest == '--' {
+					// It could be end of input (--) or another argument (--abc).
+					// Both are invalid so die.
+					unsafe { nextarg_rest.free() }
+					return []
+				}
+				unsafe { nextarg_rest.free() }
 			}
 			found_entries << fs.args[i + 1]
 			to_delete << i
@@ -158,39 +187,41 @@ fn (mut fs FlagParser) parse_value(longhand string, shorthand byte) []string {
 // -> '--flag' is parsed as true
 // -> '--flag' is equal to '--flag=true'
 fn (mut fs FlagParser) parse_bool_value(longhand string, shorthand byte) ?string {
-	full := '--$longhand'
-	for i, arg in fs.args {
-		if arg == '--' {
-			// End of input. We're done.
-			break
-		}
-		if arg.len == 0 {
-			continue
-		}
-		if arg[0] != `-` {
-			continue
-		}
-		if (arg.len == 2 && arg[0] == `-` && arg[1] == shorthand) || arg == full {
-			if fs.args.len > i + 1 && (fs.args[i + 1] in ['true', 'false']) {
-				val := fs.args[i + 1]
-				fs.args.delete(i + 1)
+	{
+		full := '--$longhand'
+		for i, arg in fs.args {
+			if arg == '--' {
+				// End of input. We're done.
+				break
+			}
+			if arg.len == 0 {
+				continue
+			}
+			if arg[0] != `-` {
+				continue
+			}
+			if (arg.len == 2 && arg[0] == `-` && arg[1] == shorthand) || arg == full {
+				if fs.args.len > i + 1 && (fs.args[i + 1] in ['true', 'false']) {
+					val := fs.args[i + 1]
+					fs.args.delete(i + 1)
+					fs.args.delete(i)
+					return val
+				} else {
+					fs.args.delete(i)
+					return 'true'
+				}
+			}
+			if arg.len > full.len + 1 && arg[..full.len + 1] == '$full=' {
+				// Flag abc=true
+				val := arg[full.len + 1..]
 				fs.args.delete(i)
 				return val
-			} else {
-				fs.args.delete(i)
+			}
+			if arg.len > 1 && arg[0] == `-` && arg[1] != `-` && arg.index_byte(shorthand) != -1 {
+				// -abc is equivalent to -a -b -c
 				return 'true'
 			}
 		}
-		if arg.len > full.len + 1 && arg[..full.len + 1] == '$full=' {
-			// Flag abc=true
-			val := arg[full.len + 1..]
-			fs.args.delete(i)
-			return val
-		}
-		if arg.len > 1 && arg[0] == `-` && arg[1] != `-` && arg.index_byte(shorthand) != -1 {
-			// -abc is equivalent to -a -b -c
-			return 'true'
-		}
 	}
 	return error("parameter '$longhand' not found")
 }
@@ -198,9 +229,15 @@ fn (mut fs FlagParser) parse_bool_value(longhand string, shorthand byte) ?string
 // bool_opt returns an optional that returns the value associated with the flag.
 // In the situation that the flag was not provided, it returns null.
 pub fn (mut fs FlagParser) bool_opt(name string, abbr byte, usage string) ?bool {
-	fs.add_flag(name, abbr, usage, '<bool>')
-	parsed := fs.parse_bool_value(name, abbr) or { return error("parameter '$name' not provided") }
-	return parsed == 'true'
+	mut res := false
+	{
+		fs.add_flag(name, abbr, usage, '<bool>')
+		parsed := fs.parse_bool_value(name, abbr) or {
+			return error("parameter '$name' not provided")
+		}
+		res = parsed == 'true'
+	}
+	return res
 }
 
 // defining and parsing a bool flag
@@ -230,12 +267,17 @@ pub fn (mut fs FlagParser) int_multi(name string, abbr byte, usage string) []int
 // int_opt returns an optional that returns the value associated with the flag.
 // In the situation that the flag was not provided, it returns null.
 pub fn (mut fs FlagParser) int_opt(name string, abbr byte, usage string) ?int {
-	fs.add_flag(name, abbr, usage, '<int>')
-	parsed := fs.parse_value(name, abbr)
-	if parsed.len == 0 {
-		return error("parameter '$name' not provided")
+	mut res := 0
+	{
+		fs.add_flag(name, abbr, usage, '<int>')
+		parsed := fs.parse_value(name, abbr)
+		if parsed.len == 0 {
+			return error("parameter '$name' not provided")
+		}
+		parsed0 := parsed[0]
+		res = parsed0.int()
 	}
-	return parsed[0].int()
+	return res
 }
 
 // defining and parsing an int flag
@@ -265,12 +307,16 @@ pub fn (mut fs FlagParser) float_multi(name string, abbr byte, usage string) []f
 // float_opt returns an optional that returns the value associated with the flag.
 // In the situation that the flag was not provided, it returns null.
 pub fn (mut fs FlagParser) float_opt(name string, abbr byte, usage string) ?f64 {
-	fs.add_flag(name, abbr, usage, '<float>')
-	parsed := fs.parse_value(name, abbr)
-	if parsed.len == 0 {
-		return error("parameter '$name' not provided")
+	mut res := 0.0
+	{
+		fs.add_flag(name, abbr, usage, '<float>')
+		parsed := fs.parse_value(name, abbr)
+		if parsed.len == 0 {
+			return error("parameter '$name' not provided")
+		}
+		res = parsed[0].f64()
 	}
-	return parsed[0].f64()
+	return res
 }
 
 // defining and parsing a float flag
@@ -295,12 +341,16 @@ pub fn (mut fs FlagParser) string_multi(name string, abbr byte, usage string) []
 // string_opt returns an optional that returns the value associated with the flag.
 // In the situation that the flag was not provided, it returns null.
 pub fn (mut fs FlagParser) string_opt(name string, abbr byte, usage string) ?string {
-	fs.add_flag(name, abbr, usage, '<string>')
-	parsed := fs.parse_value(name, abbr)
-	if parsed.len == 0 {
-		return error("parameter '$name' not provided")
+	mut res := ''
+	{
+		fs.add_flag(name, abbr, usage, '<string>')
+		parsed := fs.parse_value(name, abbr)
+		if parsed.len == 0 {
+			return error("parameter '$name' not provided")
+		}
+		res = parsed[0]
 	}
-	return parsed[0]
+	return res
 }
 
 // defining and parsing a string flag
@@ -358,22 +408,23 @@ pub fn (fs FlagParser) usage() string {
 	if no_arguments {
 		adesc = ''
 	}
-	mut use := ''
+	mut use := []string{}
 	if fs.application_version != '' {
-		use += '$fs.application_name $fs.application_version\n'
-		use += '$flag.underline\n'
+		use << '$fs.application_name $fs.application_version'
+		use << '$flag.underline'
 	}
-	use += 'Usage: $fs.application_name [options] $adesc\n'
-	use += '\n'
+	use << 'Usage: $fs.application_name [options] $adesc'
+	use << ''
 	if fs.application_description != '' {
-		use += 'Description:\n'
-		use += '$fs.application_description'
-		use += '\n\n'
+		use << 'Description: $fs.application_description'
+		use << ''
+		use << ''
 	}
 	// show a message about the [ARGS]:
 	if positive_min_arg || positive_max_arg || no_arguments {
 		if no_arguments {
-			use += 'This application does not expect any arguments\n\n'
+			use << 'This application does not expect any arguments'
+			use << ''
 		} else {
 			mut s := []string{}
 			if positive_min_arg {
@@ -386,11 +437,12 @@ pub fn (fs FlagParser) usage() string {
 				s = ['exactly $fs.min_free_args']
 			}
 			sargs := s.join(' and ')
-			use += 'The arguments should be $sargs in number.\n\n'
+			use << 'The arguments should be $sargs in number.'
+			use << ''
 		}
 	}
 	if fs.flags.len > 0 {
-		use += 'Options:\n'
+		use << 'Options:'
 		for f in fs.flags {
 			mut onames := []string{}
 			if f.abbr != 0 {
@@ -410,10 +462,11 @@ pub fn (fs FlagParser) usage() string {
 			} else {
 				xspace = flag.space[option_names.len..]
 			}
-			use += '$option_names$xspace$f.usage\n'
+			fdesc := '$option_names$xspace$f.usage'
+			use << fdesc
 		}
 	}
-	return use.replace('- ,', '   ')
+	return use.join('\n').replace('- ,', '   ')
 }
 
 // finalize - return all remaining arguments (non options).