Notices by Erin 💽✨ (erincandescent@akko.erincandescent.net), page 3

Relatedly: The %x conversion specifier in fscanf is defined in terms of strtoul. fscanf is only allowed one character of lookahead (see §7.23.6.2 footnote 332, “fscanf pushes back at most one input character onto the input stream. Therefore, some sequences that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.”). sscanf and scanf are both defined in terms of fscanf.

Consider this sequence of code:

Is the result

1. r=1 (one conversion was possible), n=1 (one byte of input consumed), o=0 (we consumed the single zero digit)
2. r=0 (no conversion was possible) because 0x is a valid prefix of a conversion specifier but is not a valid input to strtoul (see previous post)

Now consider

We have a third potential option here: r=1, n=4, o=0xAA

however per the above footnote we must pick that our result is

• (1) in both cases
• (2) in both cases
• (2) in the first case, (3) in the second

In particular combo (1) and (3) is impossible because it would require us to peak ahead two characters (xZ/xA) in order to know which of the two cases we are in

I think (1) in both cases is the only reasonable result and the standard should probably call out explicitly that the 0b/0x prefixes are not permitted for the input to the %b/%x conversion specifiers respectively.

Previous discussion on the glibc issue tracker and with the committee seems to indicate that for this case (2)/(3) is the correct result. I find this outcome emotionally upsetting (but then, that describes lots of the specifics of scanf…) but it is at least internally consistent.

glibc for the first case will currently produce r=1, n=2, o=0 which is just nonsense, but at least its acknowledged as a (very old!) bug

Anyway I think this interpretation means a C standard library implementation needs different implementations of scanf and strtoul to be conformant to both C23 and C17 and earlier.

My displeasure is imeasurable and my day is ruined.

:drgn_dizzy:

So I have set of interesting C corner cases…

Consult 7.24.1.7 of WG14 N3220, concering “The strtol, strtoll, strtoul, and strtoull functions” and then look at the following:

Note: in versions of C prior to C23, the following are unambiguous (the language permitting the 0b prefix was added in C23). Depending upon interpretation, in C23 strtoul may reject inputs that were considered acceptible in in previous versions of the standard

If the local Bäckspace was a real thing I could go there and bake up a load of Franzbrötchen right about now…

Tired: Going to the hackspace to work on your programming project
Wired: Going to the hackspace to work on your electronics project
Un-Wired: Going to the Bäckspace to work on your baking project

@alina its red eurostar! its an imposter!!

(the artist formerly known as thalys)

The “Ohh its coming to Berlin - aww its already sold out” rollercoaster :(

This is just an unreasonably cool bit of imagery, and you’re telling me its from an opera?!

@yassie_j @rail_ @jeder its kinda funny, the traditional UK train safety system (AWS+TPWS) is a kinda cobbled together mess, the speed limit is higher (125mph 201km/h) and the lines are very intensively worked yet the UK railways are among the very safest in Europe.

The most probable answer for how this happened IMO is “They put the Rail Accident Investigation Branch and the Air Accident Investigation Branch in the same office”

@trwnh @julian @thisismissem @silverpill In any case I don’t think “origin based authentication” for fetches is a good idea for the simple reason that its not, to my knowledge, what implementations do today and it strongly risks leaking private posts. Certainly what the ActivityPub spec heavily implies if not outright says is that anything fetchable via a given identity should be visible to that identity, and I’m generally iffy on the idea of trying to make implementations execute potentially complicated ACLs on behalf of each other; that way is certainly a security disaster.

So that then leaves us with the question: is leaking the identity of the actor who has pasted a post’s URL into their instance’s search bar a real issue?

@thisismissem @blogdiva @mttaggart @mwl we’re currently at 50% utilisation. We’ve already exhausted a lot of the “good” ones (pray help you if your country’s name starts with an S); if they were permanently reserved we’d run out and run into issues.

Typically they become Transitionally Reserved for 50 years, though it can be shortened to 5 years with good reason