價值暫時不可用，由於優化流

Question

我最近開始使用發佈版本（管理方案並設置從調試到發佈運行）測試我的應用程序。我注意到的是，偶爾我會在流方法中彈出以下錯誤消息，而我似乎無法找到找到錯誤的方法。這在調試模式下完美工作，但在發佈版本中，我沒有收到SIGABRT消息之外的任何通知。我也不知道如何檢查模擬器上的崩潰日誌，看看問題是什麼。下面，我附崩潰的堆棧跟蹤：從流

#0 0x918749c6 in __pthread_kill() 
#1 0x916c0f78 in pthread_kill() 
#2 0x916b1ce3 in __abort() 
#3 0x916ae64a in __stack_chk_fail() 
#4 0x00006d0d in -[MainViewController processMessage:len:] (_cmd=0x9ceb9, msg=0xdfd7004 "Login="User" Pass="Pass" Id="1234" PlayerId="345" Location="12,35" Color="Red" PlayerId="65" Location="180,0" Color="Blue" PlayerId="29" Location="0,200" Color="..., len=333295) at /Users/seb/Desktop/Tutorials/Networking/MainViewController.m:850 
#5 0x000044b3 in -[MainViewController stream:handleEvent:] (_cmd=0x17a0410, stream=<value temporarily unavailable, due to optimizations>, eventCode=<value temporarily unavailable, due to optimizations>) at /Users/seb/Desktop/Tutorials/Networking/MainViewController.m:260 
#6 0x01716501 in _inputStreamCallbackFunc() 
#7 0x016e606d in _signalEventSync() 
#8 0x016e67ca in _cfstream_solo_signalEventSync() 
#9 0x016e5e71 in _CFStreamSignalEvent() 
#10 0x016e6727 in CFReadStreamSignalEvent() 
#11 0x020083ad in SocketStream::dispatchSignalFromSocketCallbackUnlocked() 
#12 0x01f64191 in SocketStream::socketCallback() 
#13 0x01f640a1 in SocketStream::_SocketCallBack_stream() 
#14 0x016b3e44 in __CFSocketPerformV0() 
#15 0x0171997f in __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__() 
#16 0x0167cb73 in __CFRunLoopDoSources0() 
#17 0x0167c454 in __CFRunLoopRun() 
#18 0x0167bdb4 in CFRunLoopRunSpecific() 
#19 0x0167bccb in CFRunLoopRunInMode() 
#20 0x0226f879 in GSEventRunModal() 
#21 0x0226f93e in GSEventRun() 
#22 0x0066aa9b in UIApplicationMain() 
#23 0x0000201b in main (argc=1, argv=0xbffff5e0) at /Users/seb/Desktop/Tutorials/Networking/main.m:14 

Case語句：在崩潰發生在那裏的handleEvent：

case NSStreamEventHasBytesAvailable: 
     { 
      if (stream == inputStream) 
      { 
       NSLog(@"NSStreamEventHasBytesAvailable"); 

       uint8_t buffer[4096]; 
       unsigned int len = 0; 
       NSInputStream* inputstream = (NSInputStream*)stream; 
       len = [inputstream read:buffer maxLength:sizeof(buffer)]; 

       // Check if our stream is still valid 
       if([inputstream streamError] != nil) 
       { 
        //We lost our connection to the host 
        NSError *theError = [stream streamError]; 
        [self setConnectError:[NSString stringWithFormat:@"Error %i: %@", 
                  [theError code], [theError localizedDescription]]]; 

        break; 
       } 

       [streamIncomingData appendBytes:buffer length:len]; 

       int processedBytes = 0; 
       while (true) 
       { 
        if ([streamIncomingData length] >= processedBytes + sizeof(uint32_t)) 
        { 
         const char* bufferstart = ((const char*)[streamIncomingData mutableBytes]) + processedBytes; 
         uint32_t sz_n; 
         memcpy(&sz_n, bufferstart, sizeof(sz_n)); 
         uint32_t sz_h = htonl(sz_n); 

         if ([streamIncomingData length] >= processedBytes + sz_h + sizeof(uint32_t)) 
         { 
          [self processMessage:bufstart + sizeof(uint32_t) len:sz_h]; 
          processedBytes += sz_h + sizeof(uint32_t); 
         } 
         else 
         { 
          break; 
         } 
        } 
        else 
        { 
         break; 
        } 
       } 
       if (processedBytes) 
       { 
        if (processedBytes < [streamIncomingData length]) 
        { 
         NSMutableData *newdata = [NSMutableData dataWithBytes:[streamIncomingData bytes] + processedBytes length:[streamIncomingData length] - processedBytes]; 
         [streamIncomingData setData:newdata]; 
        } 
        else 
        { 
         [streamIncomingData setLength:0]; 
        } 
       } 
      } 

      break; 
     } 

而processMessage方法：

- (void)processMessage:(const char*)msg len:(int)len 
{ 
    NSLog(@"processMessage start (%d)", len); 
    { 
     char buffer[len + 1]; 
     memcpy(buffer, msg, len); 
     buffer[len + 1] = '\0'; 
     NSLog(@"%s", buffer); 
    } 

    NSLog(@"processMessage end"); 
} 

任何意見非常感謝。

Answer 1

您通過嘗試在邊界len + 1之外分配空終止符來溢出buffer而損壞了堆棧。正確的代碼是：

char buffer[len + 1]; 
    memcpy(buffer, msg, len); 
    buffer[len] = '\0'; 
    NSLog(@"%s", buffer); 

，你在做什麼，是不確定的行爲，並與被釋放模式做的是最有可能你只看到了在釋放模式這一問題的原因，優化組合不確定的行爲。