Recursion isn’t the same as as infinite loop
I don’t get your point. Just because the image gets repeated in the 4th panel doesn’t mean its recursion. It can be an infinite while loop with a state.
Now that I think about it, a recursion without a base/break condition is just an infinite loop with a state
I think modern compilers do actually compile recursion to be equivalent with an iterative model.
edit: yes when possible they will compile to be iterative, but if it can’t be written iteratively it will be a series of calls and returns. depends on the specific type of recursion it looks like.
It’s saddening to me how many times I’ve actually come across this in production.
Just because the code works doesn’t mean it should ship.
Very much needed for embedded systems, but I’m more of a
for (;;)guy myself!What language is this?
It’s C, but the unusual look of having two semicolons is the reason why I prefer it over
while (True). It feels more like “here is the weird part”.And the rare
do { /*loop*/ } while(1);Gotcha, thank you. I mostly code in bash or python.
The compiler (in C) is allowed to assume that infinite loops eventually terminate. This can lead to these kinds of loops not actually running forever when built with an optimizing compiler.
ISO/IEC 9899:2017 §6.8.5 “Iteration statements”, paragraph 6:
“An iteration statement may be assumed by the implementation to terminate if its controlling expression is not a constant expression, and none of the following operations are performed in its body, controlling expression or (in the case of a for statement) its expression-3: – input/output operations – accessing a volatile object – synchronization or atomic operations."
It can, for example, simply optimize it away, assuming non-productive infinite loops are stupid and not reflective of what the code will actually do.
if its controlling expression is not a constant expression
Pretty big caveat. If I’m reading this right
truedefinitely qualifies as a constant expression and the loop in the meme would therefore not be optimized away.There’s also this part of the standard that throws a wrench into this hypothesis:
§5.1.2.3/4: (Program execution, Observable behavior):
Accesses to volatile objects and calls to library I/O functions are observable behavior. The implementation may perform any transformation of a program, provided that the resulting program’s observable behavior is not changed.
So it seems that running forever isn’t an observable property that must be preserved when code is transformed.
Still, I think compilers try to not surprise the developer too badly and would recognize a trivial loop most of the time.
for example, simply optimize it away
Yeah, that example makes it reasonable. But the optimizer can do ridiculous stuff when it proves the loop never terminates and also assume it terminates.
The most famous example of UB bullshit is when some compilers run code that is impossible to reach just because there’s an infinite loop on the file (not even in the same function).
The lovely part about UB is it’s non-causal. The compiler can go back in time and steal Halloween candy from you when you were five and still comply with the specification.
Cute — though the visual gag fits a little better with infinite recursion that infinite loop.
Long ago, I made a four line recursive HTML that did this with frames. Browsers didn’t have protection against that at the time, so if you opened it and let it run, your machine would lock up.
Ah, the Wild Wild Web
CPU temp will be my break statement.
Let your CPU sleep.
Always check for infinite cat girl errors.
ahem Catgirls in great quantities are a feature!
The good old fork bomb.
function f while true; do f; donenot sure but for it to be a fork bomb you need something like
&in ur pseudo code to go on to the next callrn the first call of
fwithin the loop never compiles so the second doesn’t happen. So this is “just” infinite recursionpls don’t scream at me should i be wrong.
On my computer, this pushes one core to ~60%, eats ~40MB of memory over the course of about a minute and then segfaults.
I did make one small change to the condition which would mean that it would bail out if available memory got too low, but 40MB barely even registered so it was basically true the whole time. In retrospect, I probably should have been monitoring process count instead (or done both), but I guess I got away with it.
As OP says, you need to create subprocesses with
&to cause real problems.*Bash 5.2.15 / LMDE6 / who knows what other factors. Try these things at your own risk. Or better, just don’t.
You can have a non-infinite loop without a break statement, you just need a return statement in it. Also
for(;;)is much faster to write thanwhile(true).Sometimes break is undesirable. But if you want an infinite loop, please please please include a sleep. Not doing this is why my CPU stays at 100%.
