builtin: clone the strings correctly in array.push

vlib/builtin/array.v

@@ -389,7 +389,7 @@ fn (mut a array) set(i int, val voidptr) {
 
 fn (mut a array) push(val voidptr) {
 	a.ensure_cap(a.len + 1)
-	unsafe {C.memcpy(byteptr(a.data) + a.element_size * a.len, val, a.element_size)}
+	unsafe {C.memmove(byteptr(a.data) + a.element_size * a.len, val, a.element_size)}
 	a.len++
 }
 

vlib/builtin/array_test.v

@@ -1032,6 +1032,17 @@ fn test_direct_array_access_via_ptr() {
 	}
 }
 
+fn test_push_arr_string_free() {
+	mut lines := ['hi']
+	s := 'a' + 'b'
+	lines << s
+	s.free() // make sure the data in the array is valid after freeing the string
+	println(lines)
+	assert lines.len == 2
+	assert lines[0] == 'hi'
+	assert lines[1] == 'ab'
+}
+
 const (
 	grid_size_1 = 2
 	grid_size_2 = 3

vlib/v/gen/cgen.v

@@ -2907,11 +2907,19 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 			} else {
 				g.write(', _MOV(($elem_type_str[]){ ')
 			}
+			is_interface := elem_sym.kind == .interface_ && node.right_type != info.elem_type
 			if elem_sym.kind == .interface_ && node.right_type != info.elem_type {
 				g.interface_call(node.right_type, info.elem_type)
 			}
+			// if g.pref.autofree && info.elem_type == table.string_type {
+			if info.elem_type == table.string_type {
+				g.write('string_clone(')
+			}
 			g.expr_with_cast(node.right, node.right_type, info.elem_type)
-			if elem_sym.kind == .interface_ && node.right_type != info.elem_type {
+			if info.elem_type == table.string_type {
+				g.write(')')
+			}
+			if is_interface {
 				g.write(')')
 			}
 			g.write(' }))')