Once a TCP connection has been established there is no state on routers in between the 2 ends of the connection. The issue here is firewalls / NAT entries timing out. And indeed, no RSTs are sent.
We had the issue in K8s with the conntrack module set too low.
Now, you can try to put in an HTTP Keep-Alive, but that will not help you. The HTTP Keep-Alive is merely for connection re-use at the HTTP level, i.e. it doesn't close the connection: https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/...
An HTTP Keep-Alive does not generate any packages, it merely postpones the close.
A TCP Keep-Alive generates packages which resets the timers.
Mobile operating systems can use application-level keep-alive packets, because those can be easily attributed to individual applications: an applications receives a TCP/UDP packet during low-power CPU sleep mode, asks system to wake up (by e.g. taking a wake-lock), and the system takes note who caused the wake-up. TCP Keep-Alive happens below application level, so it may be disabled, even when application can still be reached.
projects that do this drive me bananas
If I had the emotional energy, I'd open a JEP for a new @java.lang.NonNullReference and any type annotated with it would be a compiler error to assign null to it
public interface Alpha {}
@java.lang.NonNullReference
public interface Beta {}
Alpha a = null; // ok
Beta b = null; // compiler error
Beta b;
if (Random.randBoolean()) {
b = getBeta();
} else {
b = newBeta();
}
Beta b;
if (true) {
b = getBeta();
} else {
b = null; // I believe this will be elided and thus technically legal
}Java really suffers with optional because the language has such love for backwards compatibility that it's extremely unlikely that nulls would even be removed from the standard library in the first place. The fact that the ecosystem relies on ugly auto wiring hacks instead of mandating explicit constructors doesn't help either.
I still remember when Java 9 introduced modules. And I’m currently pulling my hair because Java 21 renamed all javax.* into jakarta.* because Javax was a trademark of Oracle, and all libs now require a “-jakartax” version for JDK 21.
But somehow I still have to deal with nulls everywhere and erased-at-runtime generics because Java loves backwards compatibility so much. The simple fact all libs released a “-jakartax” proves the entire ecosystem is fully maintained (plus CVEs means unmaintained libs aren’t allowed in production), so they could very well release a -jdk25 version with non-null types.
> I would personally argue that exposing the 2 levels of absence is exposing an implementation details
Probably you wouldn't want to return Option<Option<X>> (or Nullable) to outside callers - maybe you want to convert None to one kind of domain-meaningful error and Some(None) to a different kind of domain-meaningful error, maybe you want to take some different codepaths to respond to "recover" from the different kinds of absence.
But it's extremely valuable to be able to compose together existing libraries that might use absence to mean something and have them just do the right thing rather than always having to worry about the edge cases where one has a kind of absence that's subtly different from the other's kind of absence. I mean fundamentally you can't ever assume that a random third-party function in Java is safe to call with null, because many of them aren't. But you also can't ever assume that a random third-party function won't return null, because some of them do. So even to just compose two functions you've got to check their docs and think about the behaviour of this special value, and it's just all so avoidable.
{}
{ "foo": null }
{ "foo": 42 }
struct Whatever {
foo: Option<Option<u32>>,
}
I'll often use this in PATCH endpoints, where not-present means to leave the current value alone, null means to unset it, and a value means to set to that value.
Anyway, I believe what you're referring to is the "?" syntax that annotates types in Kotlin but doesn't help the resulting bytecode, which means that every single library ever would need to convert to kotlin to benefit
fun doit() : java.io.InputStream? { return null }
kotlinc test.kt
javap -c test.class
public final java.io.InputStream doit();
Code:
0: aconst_null
1: areturn
That’s incorrect for Java, possibly also for C# and JS.
In any language where strings are opaque enough types [1], the in-memory representation is an implementation detail. Java has been such a language since release 9 (https://openjdk.org/jeps/254)
[1] The ‘enough’ is because some languages have fully opaque types, but specify efficiency of some operations and through it, effectively proscribe implementation details. Having a foreign function interface also often means implementation details cannot be changed because doing that would break backwards compatibility.
> JS use floating point for all numbers. The max accurate integer is 2⁵³−1
That is incorrect. Much larger integers can be represented exactly, for example 2¹⁰⁰.
What is true is that 2⁵³−1 is the largest integer n such that n-1, n, and n+1 can be represented exactly in an IEEE double. That, in turn, means n == n-1 and n == n+1 both will evaluate to false, as expected in ‘normal’ arithmetic.
The representation for C# is very much fixed, as it allows, and very commonly uses, direct access into the string buffer as a ReadOnlySpan<char> or a raw char pointer, where char is the type of UTF-16 codepoints.
JS could maybe get away with it.
I think Java moved away from this back around 8, or possibly 9.
https://stackoverflow.com/questions/689211/interop-sending-s...
>
> That’s incorrect for Java,
Maybe so, technically, but if you Base64 encode a string in a language that uses UTF-8 (or another UTF-16 with another endian) and decode it in Java, Java's UTF-16 representation will be the problem you will be dealing with.
I wonder if anyone can learn from this. I feel like I only understood what I already knew, or at least was very close to knowing. That's the same thing that happens with teaching manuals about any topic: they're organized in a way that makes sense and it's easy for people who already know the topics, but often very bad at teaching the same topics to an audience that doesn't know anything.
I think that the reason for a manual existence. To have a written record so we don't have to trust our memory. This is what most unix manuals are. You already know what the software can do, you just need to remember the specificity on how to get something done.
> often very bad at teaching the same topics to an audience that doesn't know anything.
What you need then is a tutorial (beginner seeking to learn) or a guide (beginner/intermediate seeking to do). Manuals in this case only serve to have better questions (Now you know what you don't know).
When I was a kid I was trying to learn Linux and commands and it was disappointing.
Over the years of using it I don’t need to learn it but I do need to look stuff up.
Much of it would only apply in certain relatively narrow contexts, but the contexts aren't necessarily mentioned.
Some of it appears to be just wrong.
I guess I'm saying: I would not take this literally, but as something almost like a stream-of-consciousness.
https://gekk.info/articles/traceroute.htm
(If it's outdated I'm curious if anyone knows relevant updates?)
PSA for anyone working with datetime variables!
From MDN: "For block boxes, inline boxes, inline blocks, and all table layout boxes auto resolves to 0."
I have been unable to comprehend CSS layout from any perspective: page designer, implementer, user, anything. It must have someone in mind but I have no idea who I that is.
> Unicode unification. Different characters in different language use the same code point. Different languages' font variants render the same code point differently. 語
This isn't a trap. The given example character means the same thing in Chinese and Japanese, and the Japanese version was imported from China. People from both languages recognize both font variants as the same conceptual character.
The author is making it sound like the letter 'A' in English should have a different code point than an 'A' in French. Or that a lowercase 'a' with the top tail should be a different character than a lowercase 'a' without the top tail.
Anyway, this is discussed at length in https://en.wikipedia.org/wiki/Han_unification
> There is a negative zero -0.0 which is different to normal zero. The negative zero equals zero when using floating point comparision. Normal zero is treated as "positive zero".
And there are two ways to distinguish negative zero from normal zero: By their integer bit patterns, or by the fact that 1.0/-0.0 == -Inf vs. 1.0/0.0 == +Inf.
> It's recommended to configure the server's time zone as UTC.
Big yes. I use UTC for servers, logs, photos, and anything that is worth archiving and timestamping properly. Local time is only for colloquial use.
> For integer (low + high) / 2 may overflow. A safer way is low + (high - low) / 2
Yes, but if low and high could be negative numbers, then you've just shifted the overflow to a different range. This matters for general binary search over an integer range, as opposed to unsigned binary search over an array.
> C/C++
I'm going to throw in one of my lists of pitfalls - just using integer types and arithmetic correctly in C/C++ is a massive developer trap. That's like the most basic thing in programming. https://www.nayuki.io/page/summary-of-c-cpp-integer-rules
> Rebase can rewrite history
"Can" is a weasel word; rebase does nothing but rewrite history.
A character that carries the same concept yes. A mere "font variant" no. It's absolutely a trap to think that you can safely replace one character with another just because they have the same unicode codepoint; Japanese people will avoid your product if you do this.
But we do have А and A. Even though they look the same. And unified Han characters are often quite distinct, it tripped me up as a learner of Chinese more than once. For example, a very common character '喝' (drink) looks quite a bit different: https://en.wiktionary.org/wiki/%E5%96%9D - they have a different number of strokes even. And I can't even copy-paste it here to demonstrate, because it changes form once I copy it from the Wikipedia article.
Han unification is a mess.
Kinda misleading. volatile is for memory mapped I/O and such. volatile means the memory access really happens
This isn't really a trap, and it doesn't help anyone; it looks like "I got burned but I don't want to share the specifics".
Or do you mean something else altogether by 'CSS attributes'?
Regex semantics is subtly different across languages. E.g. a{,3} matches between 0 and 3 "a" characters in Python. In JavaScript it matches the literal string "a{,3}".
Try this (you probably need to enable and generate the locale first)
echo y | LANG=lv_LV.UTF-8 grep '[a-z]'
eta: fixed regex, I had typed \L, shared from my faulty memory.
"There is no guarantee of a single total ordering of volatile writes as seen from all threads of execution"
https://learn.microsoft.com/en-us/dotnet/csharp/language-ref...
Looks like release/acquire to me? A total ordering would be sequential consistency.
"In C#, using the volatile modifier on a field guarantees that every access to that field is a volatile memory operation"
This makes it sound like you are right and the volatile keyword has the same behaviour as the Volatile class which explicitly says it has acquire-release ordering.
But that seems to contradict "The volatile keyword doesn't provide atomicity for operations other than assignment, doesn't prevent race conditions, and doesn't provide ordering guarantees for other memory operations." from the volatile keyword documentation?
https://learn.microsoft.com/en-us/dotnet/csharp/language-ref...
"When a field_declaration includes a volatile modifier, the fields introduced by that declaration are volatile fields. [...] For volatile fields, such reordering optimizations are restricted:
A read of a volatile field is called a volatile read. A volatile read has “acquire semantics”; that is, it is guaranteed to occur prior to any references to memory that occur after it in the instruction sequence.
A write of a volatile field is called a volatile write. A volatile write has “release semantics”; that is, it is guaranteed to happen after any memory references prior to the write instruction in the instruction sequence."This volatile keyword appears to only consider that specific memory location whereas the Volatile class seem to implement acquire-release.
Sequential consistency mostly become relevant when you have more than two threads interacting with both reads and writes. However, if you only have single-consumer (i.e. only one thread reading) or single-producer (i.e. only one thread writing) then the acquire-release semantics ends up becoming sequential since the single-consumer/producer implicitly enforces a sequential ordering. I can potentially see some multi-producer multi-consumer queues lock-free queues needing sequential atomics.
I think it's rare to see atomics with sequential consistency in practice since you typically either choose (1) a mutex to simplify the code at the expense of locking or (2) acquire-release (or weaker) to minimize the synchronization.
Wait, what? So you're saying this spinlock is buggy? What's the bug?
sweet mercy :O
Someone call the Inquisition
rm -rf $DIR
# Default message
$ rm -rf "${DIR:?}"
bash: DIR: parameter null or not set
# Custom message
$ rm -rf "${DIR:?It is not set OMG}"
bash: DIR: It is not set OMGI've write tons and tons of CSS, have done for a decade. I don't sit and think about the exact interactions, I just know a couple things that might work if I'm getting something unexpected.
I don't really see it possible to commit that to memory, unless I literally start working on an interpreter myself.
If you embrace that idea to the fullest, you can create some interesting designs/patterns that can be more resilient. The “downside” is that this way of writing css will likely made the pixel perfect head of the marketing department hate you unless they also write code.
I think it’s also okay to say that some ways of writing css just aren’t relevant anymore. A good parallel in mind is building construction and general carpentry. These days, a quick 2x4 stud wall or insulated concrete forms is fast, cheap, and standardized around the world. However, many craftspeople still exist that will create beautiful joinery for what is ultimately a simple thing, but we can appreciate that art standalone. With CSS, I don’t suspect we will ever need to go back to floats or crazy background images or whatever but it’s nice that those tools are still there for not only the sake of back compat, but also as a way to tinker and “craft” something bespoke for a special project or just because you like it. Education will eventually catch up and grid and flexbox will keep gaining popularity until we decide that it’s too complicated and come up with some new algorithm. That can all be true though and you can bring value as a developer without knowing every single aspect to the public API.
Also is there another way to position boxes side-by-side in an inline context without float?
Also as a corollary, I was thinking about games from the 90s I spent hundreds of hours playing back then earlier today. Bolo and Escape Velocity in particular come to mind. They were "simple" games with immense depth. But after some fruitless searching, all I find is scattered questions and comments over the last few years looking for modern equivalents are a handful of recommendations for games that are no longer developed or are defunct.
There's clear prior evidence of both success and lack of modern supply. Want to have a minimally minor successful game with established nostalgic audience? Make a new version of EV that is that game at its core. Don't be fancy, just do the thing Ambrosia did. Expand from there.
The simple model is look forward, and also look back. The first itch is small. For yourself. Find some others with a similar itch.
The hard part is pushing your idea into something more people want. That's where pg's 2013 article comes in to play. That's the hard part.
But that leaves a huge space between 0 and 10 where someone can find a successful niche.
Hell I've thought about trying to make a modern EV. It's tantalizing. But I've never made a game in my life. Ok I've rewritten Game of Life a lot. Good concept to try new ideas with. But the amount of work for a solo dev trying to recapture that original magic with no background in game dev is daunting.
Nope. It’s just bytes with no encoding.
But I agree that author's statement is wrong. Go stings are equivalent to byte slices.
bash: errexit depends on caller's context, will utterly fail you one day: https://lists.gnu.org/archive/html/bug-bash/2012-12/msg00093...
MSYS$ cat build.sh
#!/bin/bash
echo "hello, world"
MSYS$ ./build.sh
: not found: 2: build.sh
Polite projects will have .gitattributes specifying that .sh or .bash or bin/* or whatever are to always checkout with eol=lf <https://git-scm.com/docs/gitattributes#_eol>
As best I can tell, .ps1 does tolerate Unix lf but I'd bet good money that .bat and .cmd definitely do not
Is this a general fact or specific to a language?
> Blur does not consider ambient things.
Need to make that backdrop blur.
> Whitespace collapse. HTML Whitespace is Broken
I always hated that article title. It’s not broken, it’s just different from what you occasionally expected, mostly for very good reasons that let it do what you expected most of the time. I also disagreed with some significant other parts of it: https://news.ycombinator.com/item?id=42971415.
> Two concepts: code point (rune), grapheme cluster:
I have problems with this lot.
Firstly: add code units. When dealing with UTF-8 and you can access individual bytes, they’re UTF-8 code units. When dealing with UTF-16 and you can access 16-bit values, including surrogates, they’re UTF-16 code units.
Secondly: don’t talk about code points in general, talk about scalar values, which are what code points would have been were it not for that accursèd abomination UTF-16. Specifically, scalar values excludes the surrogate code points.
Sensible things work with scalar values. Python is the only thing I can think of that gets this wrong: its strings are sequences of code points, so you can represent lone surrogates (representable in neither UTF-8 nor UTF-16). This is so stupid.
Thirdly: ditch the alias “rune”, Go invented it and it never caught on. I don’t know of anything else that uses the term (though maybe a few things do), and the term rune gets used for other unrelated things (e.g. in Svelte 5).
> Some text files have byte order mark (BOM) at the beginning. For example, EF BB BF is a BOM that denotes the file is in UTF-8 encoding. It's mainly used in Windows. Some non-Windows software does not handle BOM.
BOM was about endianness, and U+FEFF. Link to https://en.wikipedia.org/wiki/Byte_order_mark. It made sense in UTF-16 and UTF-32: for UTF-16, if the file starts with FE FF it’s UTF-16BE, if FF FE it’s UTF-16LE. UTF-8 application of it was always a mess, never really caught on, and I think can fairly be considered completely obsolete now: the typical person or software will never encounter it. Very little software will actually handle it any more. Fortunately, it doesn’t tend to matter much: U+FEFF is the BOM for a reason, it’s ZERO WIDTH NO-BREAK SPACE.
> YAML:
I’d add “disallows Tab indentation”. It’s the only thing I can immediately think of that’s like that. (Make is roughly the opposite, recipe lines having to start with a single Tab. Python doesn’t let you mix spaces and tabs. These are all I can immediately think of.)