diff --git a/lib/std/fifo.zig b/lib/std/fifo.zig index c92da615f9..91d4c0330b 100644 --- a/lib/std/fifo.zig +++ b/lib/std/fifo.zig @@ -186,7 +186,9 @@ pub fn LinearFifo( } else { var head = self.head + count; if (powers_of_two) { - head &= self.buf.len - 1; + // Note it is safe to do a wrapping subtract as + // bitwise & with all 1s is a noop + head &= self.buf.len -% 1; } else { head %= self.buf.len; } @@ -376,6 +378,14 @@ pub fn LinearFifo( }; } +test "LinearFifo(u8, .Dynamic) discard(0) from empty buffer should not error on overflow" { + var fifo = LinearFifo(u8, .Dynamic).init(testing.allocator); + defer fifo.deinit(); + + // If overflow is not explicitly allowed this will crash in debug / safe mode + fifo.discard(0); +} + test "LinearFifo(u8, .Dynamic)" { var fifo = LinearFifo(u8, .Dynamic).init(testing.allocator); defer fifo.deinit();