mbrock

8,037 karmajoined قبل 18 سنة

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أول أمسdiscuss

The same basically holds for proofs in the absence of coherent global correctness criteria like, say, confluence and normalization for a lambda calculus, or soundness and completeness for a logic.

Fable's napkin estimate of the effort required to produce a passable reference semantics for Postgres, which would involve novel discoveries in denotational semantics of concurrent transactions and so on, might be in the ballpark of 30–60 years of PhD level work.

So realistically I think the only way to validate a Postgres implementation involves differential testing, fuzzing, acceptance test suites, etc. And still you'll have bugs that need to be hammered out the good old fashioned way.

الشهر الماضيdiscuss

[dead]

قبل شهرينdiscuss

Faster in what browser, by what measure, for what modules? "X is faster than Y" without any concretization is usually meaningless.

قبل شهرينdiscuss

You can do something like

       (y > 0 && x > INT_MAX - y) 
    || (y < 0 && x < INT_MIN - y)

and hope the optimizer turns it back into just checking the result. Or you use -fwrapv to concretize the ISO ambiguity and specify the natural two's complement semantics, checking overflow with the classic Hacker's Delight formula;

    ((x ^ s) & (y ^ s)) < 0

But the best way is to use the intrinsic __builtin_add_overflow or, depending on compiler support, its C23 standardization via <stdckdint.h> and ckd_add etc.

قبل شهرينdiscuss

okey dokey

قبل شهرينdiscuss

Well yeah that just means some aspects of the imaginary compiler were in some configurations approximated by some historical compiler versions and were in some cases rejected by the community (which cares about sane semantics even for behavior left undefined by ANSI/ISO) and in some cases left in as defaults but made trivially configurable for anyone who wants to define the undefined behavior.

قبل شهرينdiscuss

you mean removing the JIT?

قبل شهرينdiscuss

ok what's the alternative?

قبل شهرينdiscuss

yeah then I have to learn how it works and what it assumes and how I can control it and maybe switch to a more well behaved compiler if it's truly insane

قبل شهرينdiscuss

Right, good example, and both GCC and Clang offer well understood parameters for deciding, per compilation unit, what behavior you want for signed overflow (-fwrapv, -fno-strict-overflow, etc), so in reality it's quite far from spooky arbitrary nasal demons.

قبل شهرينdiscuss

Yet the standard does not tell you what the compilers do.

Linux works on a wide variety of platforms. It also relies on those platforms behaving predictably with respect to what the standard leaves undefined.

This description of ISO UB as a totally insane wonderland of random, malevolent semantics just doesn't describe reality.

قبل شهرينdiscuss

This is a description of an imaginary compiler, evoked by the ANSI/ISO standards documents, which has never existed and will never exist. To understand what the program will do, you just have to understand the compiler behavior on your target platforms. A helpful intuition pump is: imagine the ANSI/ISO specifications simply do not exist; now what? Well, you just continue your engineering practice, the way you would for any of the myriad languages that never even had a post hoc standards document.

قبل شهرينdiscuss

undefined behavior is the behavior of code patterns "for which this International Standard imposes no requirements" and the behavior is in fact almost always predictable and agreed upon by compiler vendors and the users of the language, which is why you are able to use programs that rely on undefined behavior probably every single second you are using the computer

edit: for example I'm typing this into Safari which means probably every key press and event is going through JSC JIT compiled functions—which have, structurally and necessarily and intentionally, COMPLETELY undefined behavior according to the spec—and yet it miraculously works, perfectly, because the spec doesn't really matter

قبل شهرينdiscuss

most languages don't even HAVE a specification so in most languages literally EVERYTHING everything is undefined behavior

قبل 5 أشهرdiscuss

If you stop trying to find something like truly ontologically novel about it, you might be able to understand what it actually is. Okay it's not impressive. It's not incredible. It's not groundbreaking new technology. It is what it is.

قبل 5 أشهرdiscuss

That kind of blanket demand doesn't persuade anyone and doesn't solve any problem.

Even if you get people to sit and press a button every time the agent wants to do anything, you're not getting the actual alertness and rigor that would prevent disasters. You're getting a bored, inattentive person who could be doing something more valuable than micromanaging Claude.

Managing capabilities for agents is an interesting problem. Working on that seems more fun and valuable than sitting around pressing "OK" whenever the clanker wants to take actions that are harmless in a vast majority of cases.

قبل 7 أشهرdiscuss

Flexner's "Understanding Wood Finishing" has a section about "the myth of food safety" that pretty directly states that food safety isn't a serious concern for fully cured finishes.

قبل 7 أشهرdiscuss

The solvents evaporate when the lacquer cures, right? A lacquered spatula or spoon could leach some plasticizers when heated up. But who on earth would go to the trouble of spray lacquering a spatula? It doesn't seem like a real concern. Wooden spoons from IKEA aren't gonna poison you!

قبل 7 أشهرdiscuss

The author seems to have forgotten to mention WHY he wants scrapers to use APIs instead of HTML.

قبل 7 أشهرdiscuss

I think all wood finishes are "food safe" once they're cured.