StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
text
Body
copied!<p><strong>Given your example</strong> and if you were using Java then the answer would be "No". In Java it is not possible for the thread to spawn and read your value before the assignment operation is complete. <em>In some other languages this might be a different story.</em></p> <p><i>"Variables shared between multiple threads (e.g., instance variables of objects) have atomic assignment guaranteed by the Java language specification for all data types except longs and doubles... If a method consists solely of a single variable access or assignment, there is no need to make it synchronized for thread-safety, and every reason not to do so for performance."</i> <a href="http://etutorials.org/Programming/Java+performance+tuning/Chapter+10.+Threading/10.6+Atomic+Access+and+Assignment/" rel="nofollow noreferrer">reference</a></p> <p>If your <code>double</code> or <code>long</code> is declared <code>volatile</code>, then you are also guaranteed that the assignment is an atomic operation.</p> <p><b>Update: </b> Your example is going to work in C++ just like it works in Java. Theoretically there is no way that the thread spawning will begin or complete before the assignment, even with Out of Order Execution.</p> <p>Note that your example is VERY specific and in any other case it is recommended that you ensure the shared resource is protected properly. The new C++ standard is coming out with a lot of atomic stuff, so you could declare your variable as atomic and the assignment operation will be visible to all threads without the need of locking. CAS (compare and set) is a your next best option.</p>

Querying!

Guidance

An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload