c / intermediate
Snippet
The volatile Qualifier for Hardware Access
The 'volatile' keyword tells the compiler that a variable's value can change at any time without any action being taken by the code. This prevents the compiler from performing optimizations like caching the value in a register.
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#include <stdio.h>void wait_for_ready(volatile int* status_reg) {while (*status_reg == 0) {// Busy wait - compiler cannot optimize this loop away}printf("Hardware is ready!\n");}int main() {int fake_reg = 0;// In real scenarios, this would be a memory-mapped I/O address// wait_for_ready(&fake_reg);return 0;}
Breakdown
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volatile int* status_reg
Indicates that the memory pointed to by status_reg is subject to external changes (e.g., hardware or interrupts).
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while (*status_reg == 0)
Without 'volatile', a compiler might assume the value never changes and turn this into an infinite loop or remove it.