[gpsd-dev] shm, volatile, etc.

[Dave Platt]

It may be old news to most, but...

https://www.kernel.org/doc/Documentation/volatile-considered-harmful.txt

http://stackoverflow.com/questions/2484980/why-is-volatile-not-considered-useful-in-multithreaded-c-or-c-programming

If you're *sure* that reordering is never going to be an issue with
accesses to the variable in question, and that the multithreaded
access to the variable can't cause anomalous behavior no matter
how race-condition-y things could ever get under the worst
possible conditions when the wind is blowing and the moon
is in the seventh house and Murphy is awake, then maybe "volatile"
is adequate.

But, based on the discussions cited above (and on the fact that I
have personally been burned by mis-using "volatile" in just this
fashion) I really don't think I'll ever depend on it again.

The following was also interesting to me:

http://www.itworld.com/security/380406/how-your-compiler-may-be-compromising-application-security

It looks to me as if many (mis)uses of "volatile" would count
as being "unstable" code, according to the definition in this
article... and might be at risk for being silently eliminated or
altered in unpredictable ways by future compilers.