From 4e62bc0b8130467b6a7b24b73911d7d2b33a9a01 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@vlang.io>
Date: Thu, 18 Mar 2021 05:41:50 +0300
Subject: [PATCH] autofree: fix free before return

---
 vlib/v/gen/c/cgen.v                          | 27 ++++++++++----------
 vlib/v/tests/valgrind/1.strings_and_arrays.v |  7 ++++-
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 600d9c946d..1bf7bb5e24 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -1768,7 +1768,7 @@ fn (mut g Gen) gen_asm_stmt(stmt ast.AsmStmt) {
 		} else {
 			g.write(' ')
 		}
-		// swap destionation and operands for att syntax 
+		// swap destionation and operands for att syntax
 		if template.args.len != 0 {
 			template.args.prepend(template.args[template.args.len - 1])
 			template.args.delete(template.args.len - 1)
@@ -4539,7 +4539,7 @@ fn (mut g Gen) return_statement(node ast.Return) {
 			styp := g.typ(g.fn_decl.return_type)
 			g.writeln('return ($styp){0};')
 		} else {
-			if g.is_autofree && !g.is_builtin_mod {
+			if g.is_autofree {
 				g.writeln('// free before return (no values returned)')
 				g.autofree_scope_vars(node.pos.pos - 1, node.pos.line_nr, true)
 			}
@@ -4680,13 +4680,24 @@ fn (mut g Gen) return_statement(node ast.Return) {
 			g.writeln('return $opt_tmp;')
 			return
 		}
+		// autofree before `return`
+		// set free_parent_scopes to true, since all variables defined in parent
+		// scopes need to be freed before the return
+		if g.is_autofree {
+			expr := node.exprs[0]
+			if expr is ast.Ident {
+				g.returned_var_name = expr.name
+			}
+			g.autofree_scope_vars(node.pos.pos - 1, node.pos.line_nr, true)
+		}
 		// free := g.is_autofree && !g.is_builtin_mod // node.exprs[0] is ast.CallExpr
+		// Create a temporary variable for the return expression
 		free := !g.is_builtin_mod // node.exprs[0] is ast.CallExpr
 		mut tmp := ''
 		if free {
 			// `return foo(a, b, c)`
 			// `tmp := foo(a, b, c); free(a); free(b); free(c); return tmp;`
-			// Save return value in a temp var so that it all args (a,b,c) can be freed
+			// Save return value in a temp var so that all args (a,b,c) can be freed
 			// Don't use a tmp var if a variable is simply returned: `return x`
 			if node.exprs[0] !is ast.Ident {
 				tmp = g.new_tmp_var()
@@ -4712,18 +4723,8 @@ fn (mut g Gen) return_statement(node ast.Return) {
 			g.expr_with_cast(node.exprs[0], node.types[0], g.fn_decl.return_type)
 		}
 		if free {
-			expr := node.exprs[0]
-			if expr is ast.Ident {
-				g.returned_var_name = expr.name
-			}
 			g.writeln(';')
 			has_semicolon = true
-			// autofree before `return`
-			// set free_parent_scopes to true, since all variables defined in parent
-			// scopes need to be freed before the return
-			if g.pref.autofree {
-				g.autofree_scope_vars(node.pos.pos - 1, node.pos.line_nr, true)
-			}
 			if tmp != '' {
 				g.write('return $tmp')
 				has_semicolon = false
diff --git a/vlib/v/tests/valgrind/1.strings_and_arrays.v b/vlib/v/tests/valgrind/1.strings_and_arrays.v
index 1676b3134b..0609361199 100644
--- a/vlib/v/tests/valgrind/1.strings_and_arrays.v
+++ b/vlib/v/tests/valgrind/1.strings_and_arrays.v
@@ -318,6 +318,11 @@ fn get_user() User {
 	return user
 }
 
+fn get_user2() User {
+	users := [User{'Peter', 25}, User{'Alice', 21}]
+	return users[0] // has to be cloned, since `users` are going to be freed at the end of the function
+}
+
 fn string_array_get() {
 	s := ['a', 'b', 'c']
 	x := s[0]
@@ -361,7 +366,7 @@ fn main() {
 	free_before_break()
 	// free_map()
 	// loop_map()
-	// free_array_except_returned_element()
+	free_array_except_returned_element()
 	println('end')
 }