Swift -Ounchecked和断言 [英] Swift -Ounchecked and Assertions

问题描述

在Swift中，ENABLE_NS_ASSERTIONS被忽略，并且断言是打开还是关闭取决于SWIFT_OPTIMIZATION_LEVEL，

In Swift, ENABLE_NS_ASSERTIONS is ignored, and whether assertions are on or off is dependent of SWIFT_OPTIMIZATION_LEVEL, see here for more information.

• assert()对-Onone处于活动状态
• assertionFailure()在以下时间处于活动状态 -Onone
• precondition()对于-Onone和-O
是活动的
• preconditionFailure()对于-Onone，-O和-Ounchecked
是活动的
• fatalError()对于-Onone，-O和-Ounchecked
是活动的

• assert() is active for -Onone
• assertionFailure() is active for -Onone
• precondition() is active for -Onone and -O
• preconditionFailure() is active for -Onone, -O and -Ounchecked
• fatalError() is active for -Onone, -O and -Ounchecked

调试和Beta版构建应具有启用的断言，发布版本应具有已禁用的断言.

Debug and Beta Builds should have assertions enabled, Release Builds should have assertions disabled.

我可以通过precondition方法在Swift中编写所有断言，并使用-Ounchecked标志编译Release版本，使用-O标志编译beta版本.

I could write all my assertions in Swift via the precondition method and compile Release builds with the -Ounchecked flag, beta builds with the -O flag.

iOS版本中的默认版本为-O.有什么建议不要使用-Ounchecked进行发行版本?这可能会导致其他哪些不良副作用?

The default in iOS for Release builds is -O. Is there anything advised against using -Ounchecked for release builds? Which other unwanted side effects could this cause?

推荐答案

您绝对应该不编译-Ounchecked以便发布，以便仅在测试时使用precondition.编译-Ounchecked还会禁用对数组越界和展开nil之类的检查，这可能会导致涉及内存损坏的一些非常讨厌的生产错误.

You should definitely not compile -Ounchecked for release in order to use precondition only while testing. Compiling -Ounchecked also disables checks for things like array out of bounds and unwrapping nil, that could lead to some pretty nasty production bugs involving memory corruption.

您可以通过swiftc的-assert-config参数独立于编译器优化设置来控制断言行为:

You can control assertion behaviour independently of compiler optimization settings via the -assert-config argument to swiftc:

$ cat assert.swift 
assert(false, "assertion asserted")
println("made it here...")
$ swiftc -Onone assert.swift; ./assert
assertion failed: assertion asserted: file assert.swift, line 1
Illegal instruction: 4
$ swiftc -O assert.swift; ./assert
made it here...
$ swiftc -O -assert-config Debug assert.swift; ./assert
assertion failed: assertion asserted: file assert.swift, line 1
Illegal instruction: 4
$ 

看起来没有Xcode Build Settings开关，但是您可以使用"Other Swift Flags"设置添加.

It doesn’t look like there’s an Xcode Build Settings toggle for this, but you can add using the "Other Swift Flags" setting.

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