為什么有時用lldb調試時“self”不可用？

Question

我嘗試在lldb上打印對象時有很多時間（當不是每次都有）時出現以下錯誤。 是否有一些構建/調試配置要更改，或者這是lldb中的錯誤？

(lldb) po userLevel
error: warning: Stopped in an Objective-C method, but 'self' isn't available; pretending we are in a generic context
error: use of undeclared identifier 'userLevel'
error: 1 errors parsing expression

我用llvm構建並且不剝離調試符號。

編輯：這是回溯：

(lldb) bt
* thread #1: tid = 0x1c03, 0x001169c5 FanCake-Beta`-[KWUserLevelController addPoints:](, _cmd=0x0029187b, points=15) + 179 at KWUserLevelController.m:53, stop reason = step over
    frame #0: 0x001169c5 FanCake-Beta`-[KWUserLevelController addPoints:](, _cmd=0x0029187b, points=15) + 179 at KWUserLevelController.m:53
    frame #1: 0x00112172 FanCake-Beta`-[KWEventRealTimeControllergameEngine:hostedGame:didSucceedIn:withScore:](self=0x0b9d7740, _cmd=0x0027a2a7, engine=0x1be5af40, game=0x1be5a850, completionTime=3.59473554800206, score=0) + 421 at KWEventRealTimeController.m:647
    frame #2: 0x0007189a FanCake-Beta`__35-[KMCatchEmGameEngine animateStep6]_block_invoke197(, finished='\x01') + 257 at KMCatchEmGameEngine.m:214
    frame #3: 0x01990df6 UIKit`-[UIViewAnimationBlockDelegate _didEndBlockAnimation:finished:context:] + 223
    frame #4: 0x01983d66 UIKit`-[UIViewAnimationState sendDelegateAnimationDidStop:finished:] + 237
    frame #5: 0x01983f04 UIKit`-[UIViewAnimationState animationDidStop:finished:] + 68
    frame #6: 0x017587d8 QuartzCore`CA::Layer::run_animation_callbacks(void*) + 284
    frame #7: 0x03634014 libdispatch.dylib`_dispatch_client_callout + 14
    frame #8: 0x036247d5 libdispatch.dylib`_dispatch_main_queue_callback_4CF + 296
    frame #9: 0x04737af5 CoreFoundation`__CFRunLoopRun + 1925
    frame #10: 0x04736f44 CoreFoundation`CFRunLoopRunSpecific + 276
    frame #11: 0x04736e1b CoreFoundation`CFRunLoopRunInMode + 123
    frame #12: 0x040367e3 GraphicsServices`GSEventRunModal + 88
    frame #13: 0x04036668 GraphicsServices`GSEventRun + 104
    frame #14: 0x01945ffc UIKit`UIApplicationMain + 1211
    frame #15: 0x000039a8 FanCake-Beta`main(argc=1, argv=0xbffff354) + 94 at main.m:13
    frame #16: 0x00002dc5 FanCake-Beta`start + 53

編輯2：當我嘗試打印本地變量時也是如此

(lldb) po currentUser
error: variable not available

如果我在代碼中放入一些NSLog（），則打印正確的值。 但不是po命令。

Answer 1

打開編譯器優化時，我通常會收到此錯誤。 編譯器將生成不一定遵循代碼邏輯流程的代碼。

轉到導航器中的項目 - >目標 - >構建設置 - >搜索優化級別 - >擴展優化級別 - >選擇調試行 - >在項目和目標的兩列中更改為無。

希望這可以幫助。

Answer 2

我遇到了這個問題，當我編輯我的方案並將Run build設置為Debug時它就消失了。 我已將其設置為AdHoc以測試推送通知，這顯然使LLDB不滿意。

Answer 3

因為它被優化了。 我們來舉個例子：

void f(int self) {
  // Here, "self" is live:Its value is used in the call to NSLog()
  NSLog(@"I am %d",self);
  // Here, "self" is dead: Its value is never used.
  // I could do self=0 or self=self*self and nobody would know.
  // An optimizing compiler will typically optimize it away.
  // It might still be on the stack (in the parameters passed to NSLog())
  // but the compiler shouldn't assume this.
  NSLog(@"Another function call: %d", 1);
  // If "self" was on the stack, it will probably now have been overwritten.
}

編譯器做了很多事情來使你的代碼更快/更小; 忘記不再需要的變量是一種非常常見的優化。

Answer 4

正如在另一個問題中所說：

在構建設置中，將預編譯前綴標題設置為NO為我修復它。