c/programmer_humor · by gandalf_der_13te@feddit.org · 1d

can somebody confirm this pls?

121 points · 19 comments · view on lemmy.world

19 Comments

You actually shouldn't do this!

This doesn't introduce a new scope, so accidentally using x outside of the case block is UB. Instead you should introduce a new scope like so:

switch (foo)  {
  case BAZ: {
    int x = ...;
    foobar(x);
  }
}

ASoftGlow@programming.dev · 17 pts · 1d (3 replies)

Can confirm

victorz@lemmy.world · 3 pts · 18h (2 replies)

Is "case expr:" really a label? You could put anything in there, like "case 42:". I don't see a label, but maybe I don't know what a label is in C.

TwilightKiddy@scribe.disroot.org · 1 pts · 11h (1 reply)

In C# it's certainly a label, it's the same syntax and you can also jump to them with goto, which is actually very convenient sometimes. As far as I know this is an ancient feature and seeing how early C# was mostly inspired by C, I would expect it to behave the same way there.

victorz@lemmy.world · 1 pts · 6h

What?

If I have a case 42: in C#, I can issue a goto 42 and resume execution after that case? Or how would that work?

From what I know, labels are only an identifier followed by a colon, like:

stop: printf("stopped.\n");

Or just the label and colon on one line and statements following on subsequent lines. I've never seen a switch case expression being called a "label". Very new to me. Would love to see a minimal demonstration example. 🙏

Edit: huh, I guess you can.

treadful@lemmy.zip · 16 pts · 1d (3 replies)

What does assigning ... do in C? Is that just default type value or something?

gratux@lemmy.blahaj.zone · 54 pts · 1d

probably just placeholder because what is actually assigned isn't relevant to the post

gandalf_der_13te@feddit.org · 30 pts · 1d (1 reply)

it's the easter egg operator. it assigns a random value to your variable. useful for when you need a quick source of good-enough randomness in computer games (/jk)

Tja@programming.dev · 11 pts · 22h

Relevant xkcd: https://xkcd.com/221/

FiskFisk33@startrek.website · 11 pts · 1d (6 replies)

question, why is a declaration not a statement?

gratux@lemmy.blahaj.zone · 35 pts · 1d

from what i could find "because it was designed that way"

For what it's worth, C23 has updated labels to allow being placed before declarations.

sik0fewl@piefed.ca · 15 pts · 1d (3 replies)

Possibly because declarations were originally not statements in C? You could only declare variables at the start of a function, but not assign them to something at the same time.

Not sure why it still wouldn’t be allowed, though, especially if an empty statement can be a statement.

balsoft@lemmy.ml · 9 pts · 1d

I think it evolved like that:

Declarations are separate entities to statements, because declarations do not translate to a machine code instruction
Labels only make sense when attached to statements because they need to point to a particular machine code instruction <-- This should have been changed at least when declarations were allowed to be mixed with statements in compound statements
Definitions are declarations plus an assignment, let's make them a subset of a declaration <-- I think this is the biggest mistake of them all
"Well, it's already been that way for 40 years, too late to change it now!"

daychilde@lemmy.world · 7 pts · 1d (1 reply)

if an empty statement can be a statement.

Sometimes saying nothing is the loudest statement you can make. ;-)

nebeker@programming.dev · 4 pts · 18h

And NOP is a perfectly reasonable instruction.

terranoid@lemmy.cafe · 5 pts · 1d

When it's designed to be an expression

while (int x = 1) { ... Modify x to eventually be zero... }

That might make sense even if it looks weird. Kinda like a for loop.

spankysalmon@fedinsfw.app · 6 pts · 1d (1 reply)

int x = ...; isn't just a declaration. Both are totally fine in most modern languages.

tias@discuss.tchncs.de · 14 pts · 22h

in most modern languages.

This post is specifically about C.

onlinepersona@programming.dev · 6 pts · 1d

wonders of C