Add hint about the return code of panic!

[dns2utf8]

I hope the link works on all cases, since the unreachable doc is copied to std:: as well.

[rust-highfive]

r? @sfackler

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[sfackler]

r? @steveklabnik

cc @rust-lang/docs

[frewsxcv]

Is this something that is guaranteed to happen across all platforms?

[steveklabnik]

it's currently hard-coded; I don't know if we want to commit to this

@rust-lang/lang

[steveklabnik]

This seems fine but I'm not sure we want to lock into 101

[steveklabnik]

it's currently hard-coded; I don't know if we want to commit to this

@rust-lang/lang

[dns2utf8]

Is there a particular reason for this return code?
I could add a hint like "this is an implementaiton detail and may change"

[frewsxcv]

Something also to consider: although unusual, it's possible to catch panics, in which case this error code mention doesn't really apply

[withoutboats]

Seems like we can't change the default, people may be relying on it. Someday maybe we could let you set the error code, no idea how though.

[alexcrichton]

This seems like a case where we want to document the current behavior but not commit to it. We've done this a few other places in libstd, can we say what happens today and then explicitly state that it may change in the future?

[steveklabnik]

@alexcrichton yeah we've done

/// # Current Implementation

in the past, could do that here as well. See https://doc.rust-lang.org/stable/std/primitive.slice.html#current-implementation

[steveklabnik]

@dns2utf8 ping! Any chance to update this PR according to the most recent comments?

[dns2utf8]

Yes, I will make it according to "current implementation"

[dns2utf8]

I think setting the error code could be done with the macro. Maybe something like this:

panic!("my {} panic","fancy" -> 23);

Where 23 would be the returned error code. The std::panic::set_hook would then also require the function to return a number.

[dns2utf8]

I noticed something odd std::sys::unix::abort_internal() is implemented with libc::abort() which just exports the function from libc.

Using the following program but the return code is 134. Do you know why?

#include<stdlib.h>intmain() {
// this will make the programm return 134 on linux-amd64 platformabort();
return42;
}

[joshtriplett]

@dns2utf8 134 is the return code for a SIGABRT:

/tmp$ (sleep 1000 ; echo return code: $?) &
[1] 3006
/tmp$ pidof sleep
3008
/tmp$ kill -ABRT 3008
bash: line 6: 3008 Aborted sleep 1000
return code: 134
[1]+ Done ( sleep 1000; echo return code: $? )

[dns2utf8]

Interesting, I did not know that.
Should I rebase the PR before merge? Would you like me to change something else?

[arielb1]

You have an overly-long line, please fix:

[00:02:23] tidy error: /checkout/src/libstd/macros.rs:29: line longer than 100 chars

I'll also ping @steveklabnik for a review.

[dns2utf8]

Cool, thank you.

[steveklabnik]

@bors: r+ rollup

[bors]

📌 Commit 133c1bc has been approved by steveklabnik