diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index 55bb6ae9a4..9dd78d74da 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -110,6 +110,8 @@ mut:
 	match_sumtype_exprs   []ast.Expr
 	match_sumtype_syms    []table.TypeSymbol
 	// tmp_arg_vars_to_free  []string
+	// autofree_pregen       map[string]string
+	autofree_tmp_vars     []string // to avoid redefining the same tmp vars in a single function
 	called_fn_name        string
 	cur_mod               string
 	is_js_call            bool // for handling a special type arg #1 `json.decode(User, ...)`
@@ -738,6 +740,7 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 	defer {
 		// If we have temporary string exprs to free after this statement, do it. e.g.:
 		// `foo('a' + 'b')` => `tmp := 'a' + 'b'; foo(tmp); string_free(&tmp);`
+		/*
 		if g.pref.autofree { // && !g.inside_or_block {
 			// TODO remove the inside_or_block hack. strings are not freed in or{} atm
 			if g.strs_to_free.len != 0 {
@@ -750,6 +753,7 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 				// g.strs_to_free.free()
 			}
 		}
+		*/
 	}
 	// println('cgen.stmt()')
 	// g.writeln('//// stmt start')
@@ -816,7 +820,20 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 		}
 		ast.ExprStmt {
 			g.write_v_source_line_info(node.pos)
+			af := g.pref.autofree && node.expr is ast.CallExpr && !g.is_builtin_mod
+			if af {
+				g.autofree_call_pregen(node.expr as ast.CallExpr)
+			}
 			g.expr(node.expr)
+			if af {
+				if g.strs_to_free.len > 0 {
+					g.writeln(';\n// strs_to_free2:')
+					for s in g.strs_to_free {
+						g.writeln('string_free(&$s);')
+					}
+					g.strs_to_free = []
+				}
+			}
 			if g.inside_ternary == 0 && !node.is_expr && !(node.expr is ast.IfExpr) {
 				g.writeln(';')
 			}
@@ -1931,14 +1948,24 @@ fn (mut g Gen) expr(node ast.Expr) {
 			// if g.fileis('1.strings') {
 			// println('before:' + node.autofree_pregen)
 			// }
-			if g.pref.autofree && node.autofree_pregen != '' { // g.strs_to_free0.len != 0 {
-				// g.insert_before_stmt('/*START2*/' + g.strs_to_free0.join('\n') + '/*END*/')
-				g.insert_before_stmt('/*START3*/' + node.autofree_pregen + '/*END*/')
-				// for s in g.strs_to_free0 {
+			if g.pref.autofree {
+				// println('pos=$node.pos.pos')
+			}
+			// if g.pref.autofree && node.autofree_pregen != '' { // g.strs_to_free0.len != 0 {
+			/*
+			if g.pref.autofree {
+				s := g.autofree_pregen[node.pos.pos.str()]
+				if s != '' {
+					// g.insert_before_stmt('/*START2*/' + g.strs_to_free0.join('\n') + '/*END*/')
+					// g.insert_before_stmt('/*START3*/' + node.autofree_pregen + '/*END*/')
+					g.insert_before_stmt('/*START3*/' + s + '/*END*/')
+					// for s in g.strs_to_free0 {
+				}
 				// //g.writeln(s)
 				// }
 				g.strs_to_free0 = []
 			}
+			*/
 		}
 		ast.CastExpr {
 			// g.write('/*cast*/')
diff --git a/vlib/v/gen/fn.v b/vlib/v/gen/fn.v
index 8c11e67d65..bb5b5a17ef 100644
--- a/vlib/v/gen/fn.v
+++ b/vlib/v/gen/fn.v
@@ -15,6 +15,11 @@ fn (mut g Gen) gen_fn_decl(it ast.FnDecl, skip bool) {
 		// || it.no_body {
 		return
 	}
+	if g.pref.autofree {
+		defer {
+			g.autofree_tmp_vars = []
+		}
+	}
 	// if g.fileis('vweb.v') {
 	// println('\ngen_fn_decl() $it.name $it.is_generic $g.cur_generic_type')
 	// }
@@ -422,9 +427,7 @@ fn (mut g Gen) method_call(node ast.CallExpr) {
 		}
 	}
 	// TODO2
-	unsafe {
-		g.generate_tmp_autofree_arg_vars(mut node, name)
-	}
+	// g.generate_tmp_autofree_arg_vars(node, name)
 	//
 	// if node.receiver_type != 0 {
 	// g.write('/*${g.typ(node.receiver_type)}*/')
@@ -541,9 +544,8 @@ fn (mut g Gen) fn_call(node ast.CallExpr) {
 		name += '_' + g.typ(node.generic_type)
 	}
 	// TODO2
-	unsafe {
-		g.generate_tmp_autofree_arg_vars(mut node, name)
-	}
+	// cgen shouldn't modify ast nodes, this should be moved
+	// g.generate_tmp_autofree_arg_vars(node, name)
 	// Handle `print(x)`
 	if is_print && node.args[0].typ != table.string_type { // && !free_tmp_arg_vars {
 		typ := node.args[0].typ
@@ -623,39 +625,44 @@ fn (mut g Gen) fn_call(node ast.CallExpr) {
 	g.is_json_fn = false
 }
 
-fn (mut g Gen) generate_tmp_autofree_arg_vars(mut node ast.CallExpr, name string) {
-	// if g.fileis('1.strings') {
-	// println('gen tmp autofree()')
-	// }
+fn (mut g Gen) autofree_call_pregen(node ast.CallExpr) {
+	g.writeln('// autofree_call()')
 	// Create a temporary var before fn call for each argument in order to free it (only if it's a complex expression,
 	// like `foo(get_string())` or `foo(a + b)`
 	mut free_tmp_arg_vars := g.autofree && g.pref.experimental && !g.is_builtin_mod &&
 		node.args.len > 0 && !node.args[0].typ.has_flag(.optional) // TODO copy pasta checker.v
-	// mut cur_line := ''
-	if free_tmp_arg_vars {
-		free_tmp_arg_vars = false // set the flag to true only if we have at least one arg to free
-		g.tmp_count2++
-		for i, arg in node.args {
-			if !arg.is_tmp_autofree {
-				continue
-			}
-			free_tmp_arg_vars = true
-			// t := g.new_tmp_var() + '_arg_expr_${name}_$i'
-			fn_name := node.name.replace('.', '_') // can't use name...
-			t := '_tt${g.tmp_count2}_arg_expr_${fn_name}_$i'
-			g.called_fn_name = name
-			str_expr := g.write_expr_to_string(arg.expr)
-			// g.insert_before_stmt('string $t = $str_expr; // new4. to free arg #$i name=$name')
-			// g.strs_to_free0 << 'string $t = $str_expr; // new5. to free arg #$i name=$name'
-			node.autofree_pregen += 'string $t = $str_expr; // new6. to free arg #$i name=$name\n'
-			// println('setting pregen to ' + node.autofree_pregen)
-			// cur_line = g.go_before_stmt(0)
-			// println('cur line ="$cur_line"')
-			// g.writeln('string $t = $str_expr; // new3. to free arg #$i name=$name')
-			// Now free the tmp arg vars right after the function call
-			g.strs_to_free << 'string_free(&$t);'
+	if !free_tmp_arg_vars {
+		return
+	}
+	free_tmp_arg_vars = false // set the flag to true only if we have at least one arg to free
+	g.tmp_count2++
+	for i, arg in node.args {
+		if !arg.is_tmp_autofree {
+			continue
 		}
-		// g.strs_to_free << (';')
+		if arg.expr is ast.CallExpr {
+			// Any argument can be an expression that has to be freed. Generate a tmp expression
+			// for each of those recursively.
+			g.autofree_call_pregen(arg.expr as ast.CallExpr)
+		}
+		free_tmp_arg_vars = true
+		// t := g.new_tmp_var() + '_arg_expr_${name}_$i'
+		fn_name := node.name.replace('.', '_') // can't use name...
+		// t := '_tt${g.tmp_count2}_arg_expr_${fn_name}_$i'
+		t := '_arg_expr_${fn_name}_$i'
+		// g.called_fn_name = name
+		used := t in g.autofree_tmp_vars
+		if used {
+			g.write('$t = ')
+		} else {
+			g.write('string $t = ')
+			g.autofree_tmp_vars << t
+		}
+		g.expr(arg.expr)
+		g.writeln(';// new af pre')
+		// Now free the tmp arg vars right after the function call
+		g.strs_to_free << t
+		// g.strs_to_free << 'string_free(&$t);'
 	}
 }
 
@@ -698,7 +705,8 @@ fn (mut g Gen) call_args(node ast.CallExpr) {
 					// g.write('_arg_expr_${g.called_fn_name}_$i')
 					// Use these variables here.
 					fn_name := node.name.replace('.', '_')
-					name := '_tt${g.tmp_count2}_arg_expr_${fn_name}_$i'
+					// name := '_tt${g.tmp_count2}_arg_expr_${fn_name}_$i'
+					name := '_arg_expr_${fn_name}_$i'
 					g.write('/*af arg*/' + name)
 				}
 			} else {
@@ -708,7 +716,8 @@ fn (mut g Gen) call_args(node ast.CallExpr) {
 			if use_tmp_var_autofree {
 				// TODO copypasta, move to an inline fn
 				fn_name := node.name.replace('.', '_')
-				name := '_tt${g.tmp_count2}_arg_expr_${fn_name}_$i'
+				// name := '_tt${g.tmp_count2}_arg_expr_${fn_name}_$i'
+				name := '_arg_expr_${fn_name}_$i'
 				g.write('/*af arg2*/' + name)
 			} else {
 				g.expr(arg.expr)
diff --git a/vlib/v/pref/pref.v b/vlib/v/pref/pref.v
index e683edafc5..d219c03496 100644
--- a/vlib/v/pref/pref.v
+++ b/vlib/v/pref/pref.v
@@ -41,8 +41,8 @@ pub enum CompilerType {
 }
 
 const (
-	list_of_flags_with_param = ['o', 'output', 'd', 'define', 'b', 'backend', 'cc', 'os', 'target-os',
-		'cf', 'cflags', 'path']
+	list_of_flags_with_param = ['o', 'd', 'define', 'b', 'backend', 'cc', 'os', 'target-os', 'cf',
+		'cflags', 'path']
 )
 
 pub struct Preferences {
@@ -342,7 +342,11 @@ pub fn parse_args(args []string) (&Preferences, string) {
 					continue
 				}
 				eprint('Unknown argument `$arg`')
-				eprintln(if command.len == 0 {''} else {' for command `$command`'})
+				eprintln(if command.len == 0 {
+					''
+				} else {
+					' for command `$command`'
+				})
 				exit(1)
 			}
 		}
diff --git a/vlib/v/tests/valgrind/1.strings_and_arrays.v b/vlib/v/tests/valgrind/1.strings_and_arrays.v
index 7d6e0998d2..245526fd9e 100644
--- a/vlib/v/tests/valgrind/1.strings_and_arrays.v
+++ b/vlib/v/tests/valgrind/1.strings_and_arrays.v
@@ -31,6 +31,7 @@ fn str_tmp_expr() {
 	println('a' + 'b') // tmp expression result must be freed
 	handle_strings('c' + 'd', 'e' + 'f') // multiple tmp expressions must be freed
 	handle_int(handle_strings('x' + 'y', 'f')) // exprs 2 levels deep must bee freed
+	handle_strings('1', add_strings('2', '3')) // test a fn that returns a string
 }
 
 fn str_tmp_expr_advanced() {
@@ -41,7 +42,8 @@ fn str_tmp_expr_advanced() {
 	// t1.free()
 	// t2.free()
 	// t3.free()
-	// handle_strings('c' + 'd', add_strings('e' + 'f', 'g')) // both lvl 1 and lvl2 exprs must be freed
+	//
+	handle_strings('c' + 'd', add_strings('e' + 'f', 'g')) // both lvl 1 and lvl2 exprs must be freed
 }
 
 struct Foo {