From 57ad943b92a797ca4782342867dcba5be0e14ead Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@vlang.io>
Date: Sat, 28 Nov 2020 15:21:53 +0100
Subject: [PATCH] autofree: free arrays on re-assignment

---
 vlib/v/gen/cgen.v                            | 37 ++++++++++++--------
 vlib/v/tests/valgrind/1.strings_and_arrays.v |  7 ++++
 2 files changed, 29 insertions(+), 15 deletions(-)

diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index 3f419c5ac5..3657273ac3 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -1538,25 +1538,32 @@ fn (mut g Gen) gen_assign_stmt(assign_stmt ast.AssignStmt) {
 	}
 	// Free the old value assigned to this string var (only if it's `str = [new value]`)
 	mut af := g.pref.autofree && !g.is_builtin_mod && assign_stmt.op == .assign && assign_stmt.left_types.len ==
-		1 && assign_stmt.left_types[0] == table.string_type && assign_stmt.left[0] is ast.Ident
+		1 && assign_stmt.left[0] is ast.Ident
+	// assign_stmt.left_types[0] in [table.string_type, table.array_type] &&
 	mut sref_name := ''
+	mut type_to_free := ''
 	if af {
-		ident := assign_stmt.left[0] as ast.Ident
-		if ident.name != '_' {
-			/*
-			g.write('string_free(&')
+		first_left_type := assign_stmt.left_types[0]
+		first_left_sym := g.table.get_type_symbol(assign_stmt.left_types[0])
+		if first_left_type == table.string_type || first_left_sym.kind == .array {
+			type_to_free = if first_left_type == table.string_type { 'string' } else { 'array' }
+			ident := assign_stmt.left[0] as ast.Ident
+			if ident.name != '_' {
+				/*
+				g.write('string_free(&')
 			g.expr(assign_stmt.left[0])
 			g.writeln('); // free str on re-assignment')
-			*/
-			sref_name = '_sref$assign_stmt.pos.pos'
-			g.write('string $sref_name = (') // TODO we are copying the entire string here, optimize
-			// we can't just do `.str` since we need the extra data from the string struct
-			// doing `&string` is also not an option since the stack memory with the data will be overwritten
-			g.expr(assign_stmt.left[0])
-			g.writeln('); // free str on re-assignment2')
-			defer {
-				if af {
-					g.writeln('string_free(&$sref_name);')
+				*/
+				sref_name = '_sref$assign_stmt.pos.pos'
+				g.write('$type_to_free $sref_name = (') // TODO we are copying the entire string here, optimize
+				// we can't just do `.str` since we need the extra data from the string struct
+				// doing `&string` is also not an option since the stack memory with the data will be overwritten
+				g.expr(assign_stmt.left[0])
+				g.writeln('); // free $type_to_free on re-assignment2')
+				defer {
+					if af {
+						g.writeln('${type_to_free}_free(&$sref_name);')
+					}
 				}
 			}
 		} else {
diff --git a/vlib/v/tests/valgrind/1.strings_and_arrays.v b/vlib/v/tests/valgrind/1.strings_and_arrays.v
index b1a93321f1..f91305f748 100644
--- a/vlib/v/tests/valgrind/1.strings_and_arrays.v
+++ b/vlib/v/tests/valgrind/1.strings_and_arrays.v
@@ -106,6 +106,12 @@ fn reassign_str() {
 	s = s + '!' // old s ref must be copied and freed after the assignment, since s is still used in the right expr
 }
 
+fn reassign_arr() {
+	mut x := [1, 2, 3]
+	// x must be freed before the re-assignment
+	x = [4, 5, 6]
+}
+
 fn match_expr() string {
 	x := 2
 	res := match x {
@@ -266,6 +272,7 @@ fn main() {
 	println('start')
 	simple()
 	reassign_str()
+	reassign_arr()
 	str_tmp_expr()
 	str_tmp_expr_advanced()
 	str_tmp_expr_advanced_var_decl()