STM32 single chip microcomputer -- volatile keyword

1. Application scenarios

volatile Keyword analysis , It is often used in three occasions

1） When multithreaded programming shares global variables , The global variable needs to be added with volatile To embellish , Let the compiler not optimize the variable .

2） During bare metal programming , When a function shares a global variable with an interrupt service function , The global variable needs to be added with volatile To embellish , Let the compiler not optimize the variable .

3）ARM When the register is defined , A register points to an address , To add volatile To embellish , Let the compiler omit access to the variable without optimization .

The compiler should not optimize this variable, which means to prevent the compiler from over Optimizing , Cause code operation failure .

add volatile The assembly code generated by keywords will change significantly , Also called delay function , The speed of the lamp changes ！

2. Example

delay Function in -O2 Grade , Whether to add volatile keyword , Disassembly analysis .