robryk @robryk@qoto.org

@kuba

Może używają tego do rozpoznawania ciebie z większych odległości? Z większych odległości dobrze widać kolor, a gorzej cokolwiek związanego z krojem, więc to pasuje do ich błędnego założenia.

(Wydaje mi się, że u mnie rozkład tego, które ubrania i jakie ich własności pamiętam pasuje do tego. Np. kojarzę kolor czepka i ramiączek kostiumu pływackiego większości moich znajomych, podobnie kolor ubrania na narty. Słabiej kojarzę kolory np. spodni, które typowo noszą.)

@matt @b0rk

Pedantic investigator ("let me see what this thing actually does and what edge cases it has") is related but am not sure if identical.

@b0rk

Question answerer strongly reminds me of https://en.wikipedia.org/wiki/The_Steerswoman

@rysiek

A way of using it that I found not irritating was to use it for questions of examples of things where (a) you are reasonably convinced they don't exist (b) it's easyish to verify if they do (e.g. molecules that contain helium). You don't run the risk of being fooled by its overeloquence on account of (a), and you don't end up unsure on account of (b). (The way (b) works is usually by way of you looking for a name of a thing that you can then look up.)

@avolha

Nie rozumiem tak dużego wzburzenia na temat tego, że atak DoS zatrzymujący pociągi da się przeprowadzić np. z samolotu. Jeśli ktoś by to uczynił to (a) bardzo łatwo byłoby stwierdzić, który samolot to robi (b) mógłby spowodować większe zamieszanie nadając np. fałszywe sygnały GPS.

@danluu

Might some of them be unable to see what's in front of you (as in, unable to see that you can't overtake the obstruction)?

@rq

BTW. https://github.com/google/wuffs/blob/main/doc/spec/rac-spec.md is an example of a spec that describes what a decoder must do, in a case where there are nontrivial constraints on it (that serve to make sure that you can't construct a compressed file that will decompress differently depending on whether you read from the beginning or not).

@rq

Well, it's a spec for the format. It says things like "a valid ZIP file MUST ...", but doesn't specify the behaviour of the parser (can the parser assume that this holds? must the parser fail if it doesn't hold? what if it doesn't hold in a part of the file the parser wouldn't even ordinarily read? etc.).

Quick grepping through those appnotes doesn't reveal any expectations around path other than ones in 4.4.17, which don't specify anything about uniqueness (nor about interpretation of nonuniqueness, but that is not something I'd expect in a specification of format as opposed to parsing).

@rq

Why isn't this just <insert archive format you like> base64-encoded?

@rq

Is the zip format standardized, or parsing of zips? Without looking I expect the former, because there are multiple ways to parse a zipfile: there's the infamous "does first or last entry for a given path count" problem (exacerbated by the distinction between "first in the directory in footer" and "first in byte order in the file itself").

@kravietz @EugeneMcParland @vfrmedia

The unprotectedness of the mechanism is (or maybe was) IMO a feature: it's hard to conceive of a way in which e.g. some trains obey a stop signal while others don't (as long as they have their radios set to the locally-correct channel). The extent of testing of train-local systems consists of sending the signal on a test channel (and making sure a test receiver acknowledged it) and asking a test transmitter to send a signal on the test channel (and checking that the appropriate actuation happened). If there was any authentication, then there'd be more potential failure modes.

@grrrr_shark

Sure, I get that _this_ is very different (both in mean and variance). But aren't the effects of trying to stay well above the-value-that-got-randomized-for-today similar? (Or are you saying that for many people this range starts so high that they never get to experience trying to stay in it for more than a day at a time?)

@grrrr_shark

Huh. I thought this is a universal property of humans (for basically any axis of capacity I can think of).

@koakuma

By "not seeing hazard pointers used outside of theory" I meant that in places which would use them I'd see RCU used instead (with the thing that deallocates -- which might be a thing to the side of everything else -- waiting on the RCU "lock").

@koakuma

I was under the impression that ll/sc in hardware is terribly rare, so everyone makes do with CAS. They then use of the tricks to prevent ABA in CAS-based setups (either counters we trust to never wrap around, or pointers to objects that the actor who does the CAS keeps alive[1]). If we had ll/sc those tricks would be unnecessary.

So, I think that people don't use that property of ll/sc because they don't use ll/sc, because it's very rarely available.

[1]
roughly:
- read ptr from X
- increment refcount on *ptr
- read X again, verify it's still equal to ptr (if not: decrement refcount, start from scratch)
- ...
- CAS X from ptr to something else
- decrement refcount on *ptr (and potentially handle the case when it decrements to 0)

This guarantees ABA-freeness of the CAS if each potential target of the pointer in X can become it only once in its lifetime (which is pretty common in structures such as queues, stacks, approximate queues, ...).

This is a reasonably common pattern in lockfree data structures that need to do their own memory management (i.e. for environments without a garbage collector) and that don't want to use thread IDs (if they can, refcounts often get replaced with hazard pointers; that said, I've never seen hazard pointers used outside of theory).

@LukaszOlejnik

There was a case 10~20 years ago of a teenager who started triggering emergency stop for fun using self-modified radio equipment. I was actually surprised that no vandalism-leaning person did something similar in a massively disruptive way (by hiding multiple transmitters and doing so in a well-chosen location), so I wouldn't exclude the vandalism hypothesis yet.

BTW. The physical proximity requirement is not that strong: the range is limited by terrain and R^2, and fixed transmitters of rail dispatchers have a range of iirc small tens of km. I would wager that using a transmitter with ERP of 100W or so from a good vantage point would give you at least as much.

@rysiek

OT: co dokładnie znaczy ogólnobojowy?