builtin: add &u8.free()

vlib/builtin/array.v

@@ -1058,6 +1058,12 @@ pub fn (data &u8) vbytes(len int) []u8 {
 	return unsafe { voidptr(data).vbytes(len) }
 }
 
+// free frees the memory allocated
+@[unsafe]
+pub fn (data &u8) free() {
+	unsafe { free(data) }
+}
+
 @[if !no_bounds_checking ?; inline]
 fn panic_on_negative_len(len int) {
 	if len < 0 {

vlib/v/gen/c/autofree.v

@@ -205,7 +205,7 @@ fn (mut g Gen) autofree_var_call(free_fn_name string, v ast.Var) {
 		return
 	}
 	mut af := strings.new_builder(128)
-	if v.typ.is_ptr() {
+	if v.typ.is_ptr() && v.typ.idx() != ast.u8_type_idx {
 		af.write_string('\t')
 		if v.typ.share() == .shared_t {
 			af.write_string(free_fn_name.replace_each(['__shared__', '']))
@@ -241,7 +241,7 @@ fn (mut g Gen) autofree_var_call(free_fn_name string, v ast.Var) {
 			af.writeln('\tif (${c_name(v.name)}.state != 2) {')
 			af.writeln('\t\t${free_fn_name}((${base_type}*)${c_name(v.name)}.data); // autofreed option var ${g.cur_mod.name} ${g.is_builtin_mod}')
 			af.writeln('\t}')
-		} else {
+		} else if v.typ.idx() != ast.u8_type_idx {
 			af.writeln('\t${free_fn_name}(&${c_name(v.name)}); // autofreed var ${g.cur_mod.name} ${g.is_builtin_mod}')
 		}
 	}

vlib/v/tests/u8_free_test.v

@@ -0,0 +1,11 @@
+fn test_main() {
+	unsafe {
+		mut data := malloc(4)
+		data[0] = c'f'
+		data[1] = c'o'
+		data[2] = c'o'
+		data[3] = c'\0'
+		assert data.vstring() == 'foo'
+		data.free()
+	}
+}