https://issues.dlang.org/show_bug.cgi?id=19836
Dlang Bot <[email protected]> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution|--- |FIXED --- Comment #2 from Dlang Bot <[email protected]> --- dlang/phobos pull request #6985 "Fix Issue 19836 - Excessive probability of UUID collisions in std.uuid.randomUUID" was merged into master: - 5d0f1d3471b95d6d22406001f3e7ba52b4691aa2 by Nathan Sashihara: Fix Issue 19836 - Excessive probability of UUID collisions in std.uuid.randomUUID On 64-bit architectures use 64 bits of entropy to initialize thread-local `rndGen`. The motivation for this change is std.uuid defaults to using `rndGen` to generate UUIDs. If every `rndGen` starts in one of 2^^32 states then if 77000 independent programs each generate a single UUID there is a 50% chance that at least two of them generate the same initial UUID (and all subsequent UUIDs would be identical as well). Not just Phobos but also C++ boost::uuids::random_generator defaults to generating UUIDs with a Mersenne Twister initialized from a 32-bit seed, exacerbating the collision problem further. If instead there are 2^^64 possible initial states of `rndGen` there can be over 5 billion independent `rndGen`s before there is a 50% chance of two having identical initial states. This change is limited to 64-bit architectures to avoid a measurable performance decrease, because many programs are not generating UUIDs. https://github.com/dlang/phobos/pull/6985 --
