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Chess.com stopped working on 32bit iPads because 2^31 games have been played

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Re: Chess.com stopped working on 32bit iPads because 2^31 games have been played

#271

Post by mishoo »

chesserik wrote: post #76
Aloha wrote: post #60

Earlier quoted context omitted.

2 billion is a very large number that was probably not envisioned as reachable in the near future - as a programmer I'd argue this is a pretty easy mistake to make, and that while (slightly) embarrassing, its a good learning moment. It's also really awesome that you're here, and that you guys were so honest about the nature of the bug - this is really something that should be encouraged.

Maybe we should start a blog about all of the interesting bugs and challenges we encounter. It certainly is white-knuckle pretty often when running at scale. The number of devices, connections, features... I'm aging prematurely :P

Agree with Aloha. I wouldn't be too hard on the programmer (also, if I understand correctly it's not a database issue, but only with the 32-bit iOS client). I'd pat him on his back and say “you didn't think we'd get this big, eh?” ;-)

Re: Chess.com stopped working on 32bit iPads because 2^31 games have been played

#272

Post by dspillett »

jfultz wrote: post #152
eponeponepon wrote: post #16

It's fascinating... the Y2K problem never came to fruition because - arguably - of the immense effort put in behind the scenes by people who understood what might have happened if they hadn't. The end result has been that the entire class of problems is overlooked, because people see it as having been a fuss over nothing. I sometimes think it would've been better if a few things had visibly failed in January 2000.

If you were watching closely and knew what to look for in the first couple of months of 2000, the failures were there. But they were generally minor and easy to overlook as Y2K problems. I spotted something like half a dozen failures in various systems I interact with which I strongly suspected, based upon the timing, were likely Y2K problems that slipped through testing. For example, I received duplicate bills for o…

> in the first couple of months of 2000, the failures were there.

They were there before then too. Things that could go wrong at midnight on NYE were only one of a few classes of problem associated with roll-overs. There were a lot of bugs in like scheduling applications (and similar system tools) in the run up to 2000 that the man on the street didn't associate with the Y2K issue because it didn't happen at that exact moment.

Re: Chess.com stopped working on 32bit iPads because 2^31 games have been played

#273

Post by devrandomguy »

smitherfield wrote: post #23
ericfriday wrote: post #10

This reminds me YouTube changed its view counter from 32-bit integers to 64-bit integers due to the popularity of 'Gangnam style' https://www.wired.com/2014/12/gangnam-style-youtube-math/

That was a joke; it was always a 64-bit integer.

I visited that video specifically because the view counter was jammed at UINT_MAX. There were comments confirming that everyone was now visitor number 4,294,967,295. In fact, it might have been an HN post that brought it to my attention; I totally didn't get sidetracked on YT and end up watching K-pop all afternoon.

Re: Chess.com stopped working on 32bit iPads because 2^31 games have been played

#274

Post by masklinn »

majewsky wrote: post #98
fpgaminer wrote: post #81

Earlier quoted context omitted.

> If you want specific sizes I would go further and say you should _always_ use specific sizes, unless forced otherwise. There's no reason not to.

There's a usecase for lower-bounded types such as int_least32_t, where the compiler may choose a larger type if it offers better performance. However, if you're using that, the test suite should run all relevant tests for multiple actual sizes of that particular type (through strategic use of #define, for example).

> There's a usecase for lower-bounded types such as int_least32_t, where the compiler may choose a larger type if it offers better performance.

If you're looking for the best performances you shouldn't use leastX types, you should use fastX types (e.g. int_fast32_t for the "fastest integer type available in the implementation, that has at least 32 bits").

The difference between "leastX" and "fastX" is that "leastX" is the smallest type in the implementation which has at least X bits. So if the implementation has 16, 32 and 64b ints and is a 32b architecture, least8 would give you a 16b int but fast8 might give you a 32b one.

Re: Chess.com stopped working on 32bit iPads because 2^31 games have been played

#276

Post by masklinn »

vxxzy wrote: post #3

How many other examples like this have occurred throughout computing history?

A counter overflow factored in the THERAC-25's race condition (one of the software's interlock was an overflowable counter rather than a flag, if the operator started treatment right as the counter overflowed the system would proceed rather than refuse).

Re: Chess.com stopped working on 32bit iPads because 2^31 games have been played

#277

Post by Piskvorrr »

wpietri wrote: post #56
justin66 wrote: post #36

Earlier quoted context omitted.

> I sometimes think it would've been better if a few things had visibly failed in January 2000. Having to spend billions of dollars on programmers' goofy means of saving a few bytes of memory is a pretty visible failure.

Nope. Definitely not goofy. My dad was a programmer in the early days. The machines he started on in the 1960s had 8 KB of RAM. Saving a byte then is the equivalent today of saving 1 MB on an 8 GB machine. Multiply that times, say, the thousands of customer orders you're trying to process and the goofy thing would be burning a lot of additional RAM because it might help somebody 35 years later. Who among us is writin…

Sometimes this worry is thrust upon you by the problem domain. I do remember tackling the Y2K38 problem in 2008 - the business logic dictated that the expiration date should be tracked, and some of them were set to 30 years.

Re: Chess.com stopped working on 32bit iPads because 2^31 games have been played

#278

Post by Piskvorrr »

brianwawok wrote: post #120
WrtCdEvrydy wrote: post #106

Earlier quoted context omitted.

Also see: IPv4 vs IPv6. Remember, these fancy computing devices were built for the rich and the government, not for the average joe, noone thought computing would be this easily accessible.

Except that isn't a great example because with Nat, ip4 can get us oodles of devices still. Can't really use NAT on a primary key...

Sure. Now ping my computer at 10.3.1.4

Re: Chess.com stopped working on 32bit iPads because 2^31 games have been played

#279

Post by cesarb »

e28eta wrote: post #228
cesarb wrote: post #183

Earlier quoted context omitted.

On a 32-bit system, a "long" is usually also 32 bits. On a non-Microsoft 64-bit system, a "long" is usually 64 bits. On both 32-bit and 64-bit systems (Microsoft or not), an "int" is usually 32 bits. If the issue happened only on 32-bit iPads, but not on 64-bit iPads, the programmer probably picked a "long", not an "int". Had the programmer picked an "int", the problem would also happen on 64-bit iPads.

Our iOS app with Java backend was using long for database IDs on both ends. I was going through the ILP32->LP64 conversion process and when I realized we had a pretty serious discrepancy. I think it's a really easy mistake for the first developer to make (especially because they weren't a C/Obj-C programmer), and then the sort of thing that no one audits after that.

Yeah, Java always uses 64 bits for "long", even on 32-bit systems. Which only adds to the confusion, since it's different from C and C++.

(Another place where Java is confusingly different: "volatile" implies a memory barrier in Java, but not in C and C++.)

Re: Chess.com stopped working on 32bit iPads because 2^31 games have been played

#280

Post by Piskvorrr »

DCoder wrote: post #89
pram wrote: post #55

I recently experienced a nasty bug with BLOB in MySQL. The software vendor was storing a giant json which contained the entire config in a single cell. It ran fine for months, and then when it was restarted it totally broke. Reason was: the json had been truncated the entire time in the database, so it was gone forever. It was only working because it used the config stored in memory on the local system. Nasty!

MySQL's silent data truncation is such a nuisance. It's off by default in 5.7, and can be disabled in earlier versions by adding STRICT_ALL_TABLES/STRICT_TRANS_TABLES to sql_mode [1]. I inherited a system where, among other things, the entire response body from a payment gateway callback is saved into a text field using utf8 character set, despite the fact that most of the supported payment gateways send data in iso-…

Early web had these issues as well: server sends response with Content-Type: text/html; charset=win-1251 (or no charset), but body contains meta charset=utf-8. MSIE worked around that in IE4 by comparing the letter frequencies to a hardcoded table and guessing the charset from there. It sort of worked, 80/20.
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