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War story: the hardest bug I ever debugged

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Re: War story: the hardest bug I ever debugged

#191

Post by GianFabien »

friendzis wrote: post #54

My hardest bug story, almost circling back to the origin of the word. An intern gets a devboard with a new mcu to play with. A new generation, but mostly backwards compatible or something like that. Intern gets the board up and running with embedded equivalent of "hello world". They port basic product code - ${thing} does not work. After enough hair are pulled, I give them some guidance - ${thing} does not work. Okay…

what if reading the state register gave back the value written?

I've had that experience. Turned out some boards in the wild didn't have the bodge wire that connected the shift register output to the gate that changed the behavior.

Re: War story: the hardest bug I ever debugged

#192

Post by pas »

jakevoytko wrote: post #15
gertlex wrote: post #13

Earlier quoted context omitted.

I also came to the comments to weigh in on my perception of how rough this was, but instead will ask: Regarding "exhausting 2-day brute-force grind": is/was this just how you like to get things done, or was there external pressure of the "don't work on anything else" sort? I've never worked at a large company, and lots of descriptions of the way things get done are pretty foreign to me :). I am also used to being abl…

The fatal error volume was so overwhelming that we didn't have any option but understanding the problem in perfect detail so that we could fix it if the problem was on our side, or avoid it if it was caused by something like our compiler or the browser. Our team also had a very grindy culture, so "I'm going to put in extra hours focusing exclusively on our top crash" was a pretty normalized behavior. After I left tha…

Was there an option to roll back Google Docs to an earlier release? Or do shadow release A/B testing for a fraction of users?

(And thanks for the war story!)

Re: War story: the hardest bug I ever debugged

#193

Post by bryanrasmussen »

saghm wrote: post #187
bryanrasmussen wrote: post #25

Earlier quoted context omitted.

>I followed all of this up until here. JavaScript lets you modify the length of an array by assigning to indexes that are negative? This is my no doubt dumb understanding of what you can do, based on some funky stuff I did one time to mess with people's heads do the following const arr = []; arr[-1] = "hi"; console.log(arr) this gives you "-1": "hi" length: 0 which I figured is because really an array is just a speci…

You raise a good point that JavaScript arrays are "just" objects that let you assign to arbitrary properties through the same syntax as array indexing. I could totally imagine some sort of optimization where a compiler utilizes this to be able to map arrays directly to their underlying memory layout (presumably with a length prefix), and that would end up potentially providing access to it in the case of a mistaken a…

yeah you know what you said made me think about these funny experiments that I haven't done in a long time and I remember now yeah, you can do

const arr = []; arr[false] = "hi";

which console.log(arr); - in FF at least - gives

Array []

false: "hi"

length: 0

which means

console.log(arr[Boolean(arr.length)]); returns

hi

which is funny, I just feel there must be an exploit somewhere among this area of things, but maybe not because it would be well covered.

on edit: for example since the index could be achieved - for some reason - from numeric operation that output NaN, you would then have NaN: "hi", or since the arr[-1] gives you "-1": "hi" but arr[0 -1] returns that "hi" there are obviously type conversions going on in the indexing...which just always struck me as a place you don't expect the type conversions to be going on the way you do with a == b;

Maybe I am just easily freaked out by things as I get older.

Re: War story: the hardest bug I ever debugged

#194

Post by saagarjha »

ivraatiems wrote: post #133
aetimmes wrote: post #120

(disclaimer: I know OP IRL.) I'm seeing a lot of comments saying "only 2 days? must not have been that bad of a bug". Some thoughts here: At my current day job, our postmortem template asks "Where did we get lucky?" In this instance, the author definitely got lucky that they were working at Google where 1) there were enough users to generate this Heisenbug consistently and 2) that they had direct access to Chrome dev…

Imagine if you weren't working at Google and were trying to convince the Chromium team you found a bug in V8. That'd probably be nigh-impossible. One thing I notice is that Google has no way whatsoever to actually just ask users "hey, are you having problems?", a definite downside of their approach to software development where there is absolutely no communication between users and developers.

I think you could, but you'd need a very convincing bug report.
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