[dbaupp]

> Even through the compiler will read a `volatile` variable from memory every time, that memory may still have a stale value in the CPU cache, which `volatile` will do nothing to prevent

FWIW, it doesn't even do this, it's just a compiler-level annotation:

  volatile int x = 0;
  int foo() {
    // read
    int ret = x;
    (void)x;

    // write
    x = 0;
    x = 1;

    return ret;
  }

The 'volatile' ensures that that code results in two reads and two writes. Removing it allows the compiler to optimise down to the equivalent of 'int ret = x; x = 1; return ret;', but both with and without use the exact same read/write instructions (i.e. have the same interaction with the cache): mov on x86 and ldr/str on ARM.

[dreta]

Nobody's arguing that volatile has anything to do with CPU cache, or barriers, or locks, or any other nonsense! volatile is there to ensure that the compiler generates code that accesses the variable directly each time, which is necessary to write correct multi-threaded code. If you don't use volatile, and your code still works, then either the compiler's smarter than you, or you got lucky. End of story. The level of misunderstanding you guys are showing on the matter is beyond comical.

volatile's one of the simplest modifiers to understand if you care to actually learn the language. It has a clear, and well-defined purpouse, and i have no idea how you can spend so much time, and energy arguing that that's not the case.