c - 内联 if (? :) doesn't work in _delay_us()

Question

当我试图在我的 1-Wire 实现中使用 _delay_us(condition ? value_if_true : value_if_false) 时，延迟不起作用，我的设备没有得到任何响应，但它工作正常当我将其替换为:

if(condition) _delay_us(value_if_true);
else _delay_us(value_if_false);

当我在 lcd 上显示内联 if 值时，它显示正确的值。

那么这两种表示法有什么区别呢？如果在 _delay_us() 中工作，我如何进行内联？

Answer 1

documentation明确地说:

In order for these functions to work as intended, compiler optimizations must be enabled, and the delay time must be an expression that is a known constant at compile-time. If these requirements are not met, the resulting delay will be much longer (and basically unpredictable), and applications that otherwise do not use floating-point calculations will experience severe code bloat by the floating-point library routines linked into the application.