External interrupts cannot be accessed. Just delete the code and restore it Record this unexpected bug

51 SCM configuration external interrupt 0/1 Nothing more than the following lines of code .

IT0=1;	// External interrupt 0 Falling edge trigger 
EX0=1;	// Allow the interrupt 0
IT1=1;	// External interrupt 1 Falling edge trigger 
EX1=1;// Allow the interrupt 1
EA=1;	// Open total interrupt 

But I spent the whole night debugging , Still can't press the key （ External interrupt 0/1 The buttons INT0/INT1） Enter external interrupt 0/1.

Finally, I put the main function and external interrupt 0/1 All codes in are deleted , Only the lighting code is left in the interrupt , then ctrl+z Undo delete , After restoring all , recompile , Not a single line of code has been changed , But I found the key （ External interrupt 0/1 The buttons INT0/INT1） It can trigger an external interrupt .

I have met this situation once before , But I don't know what the problem is , Change it the next day and you can use it , Meet again today , Got my attention .
I guess it's because keil of use C, Every time you compile C There are some differences in language optimization , Resulting in this inexplicable bug, If you use assembly or add volatile Keywords should not encounter this situation .
volatile keyword , Because the speed of memory access is far less than CPU Of , To speed up , By default , The compiler will optimize for you , For example, the data that should be fetched from the memory unit ,for Recycle 10 Time , For convenience , It will be optimized into registers , You can get the register every time , No need to access memory units again and again . And such optimization sometimes makes unexpected mistakes .