iOS Swift-某些设备上的EXC_BAD_INSTRUCTION [英] iOS Swift - EXC_BAD_INSTRUCTION on certain devices
问题描述
我对Swift和iOS开发非常陌生,但是遇到了一个错误,该错误导致在以下设备上运行时我的应用崩溃:
I'm very new to Swift and iOS development but I've come across a bug that is causing my app to crash when running on the following devices:
iPhone 4S
iPhone 5
iPad 2
iPad Retina
iPhone 4S iPhone 5 iPad 2 iPad Retina
这里是被标记的代码:
// bin2dec - converts binary string into decimal string
func bin2dec(input: String) -> String {
var counter = countElements(input)
var digit: Character
var power = 1
var result = 0
while counter > 0 {
digit = input[advance(input.startIndex, counter-1)]
switch digit {
case "0":
result += 0
case "1":
result += 1 * power
default:
power = power / 2
break
}
counter--
power *= 2
}
return "\(result)"
}
,错误是:
Thread 1: EXC_BAD_INSTRUCTION(code=EXC_I386_INVOP,subcode=0x0)
任何帮助将不胜感激!
推荐答案
iPhone 4S,iPhone 5,iPad 2,iPad Retina是32位设备,其中 Int
是一个32位整数。因此,以
iPhone 4S, iPhone 5, iPad 2, iPad Retina are 32-bit devices, where Int
is a 32-bit integer. Therefore starting with
var power = 1
然后调用
power *= 2
32次将溢出并导致异常。在Swift中,除非您明确使用溢出运算符 & *
,否则整数算法不会像(Objective-)C,
中那样默默地环绕, & +
等。
32 times will overflow and cause an exception. In Swift, integer arithmetic does not silently "wrap around" as in (Objective-)C,
unless you explicitly use the "overflow operators" &*
, &+
etc.
可能的解决方案:
- 使用
Int64
代替Int
。 - 避免最后乘以
次幂
(其结果不需要
)。
- Use
Int64
instead ofInt
. - Avoid the final multiplication of
power
(whose result is not needed).
请注意,有一些简单的方法可以将
二进制数字字符串转换为数字,例如,参见。
Note that there are simpler methods to convert a string of binary digits to a number, see for example How to convert a binary to decimal in Swift?.
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