[concurrency-interest] Volatile happens before question

Vitaly Davidovich vitalyd at gmail.com
Tue Jan 17 18:31:58 EST 2012

No. You lost the transitive relationship of happens-before with your second
statement. Your code can be reordered and executed as follows:

Thread 1 Thread 2 if (!a) // sees false a = true b = 1; bStore =b; print //
prints 1

This actually isn't valid because in original code nothing would print if a
is false - it doesn't enter the if block.  However, compiler can simply
move b=1 before a =true as that's permissible and maybe it'll do that for
some register allocation purposes, as an example.

Sent from my phone
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