ICE on no_mangle.

[adambirtles]

rustc seems to panic whenever I compile this code:

#![feature(no_std)]
#![feature(lang_items)]

#![no_std]

#[lang = "phantom_fn"]
trait PhantomFn<A: ?Sized, R: ?Sized = ()> { }

#[lang = "sized"]
trait Sized: PhantomFn<Self> { }

#[lang = "copy"]
trait Copy: PhantomFn<Self> { }

#[lang = "sync"]
trait Sync: PhantomFn<Self> { }

#[no_mangle]
pub fn main() {
}

I expected to see the code compile neatly (as it did when I tried yesterday) but this is what I got:

Assertion failed: (isa<X>(Val) && "cast<Ty>() argument of incompatible type!"), function cast, file /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/llvm/include/llvm/Support/Casting.h, line 237.
Abort trap: 6

Meta

rustc --version --verbose:

rustc 1.0.0-nightly (522d09dfe 2015-02-19) (built 2015-02-20)
binary: rustc
commit-hash: 522d09dfecbeca1595f25ac58c6d0178bbd21d7d
commit-date: 2015-02-19
build-date: 2015-02-20
host: x86_64-apple-darwin
release: 1.0.0-nightly

Backtrace:

Assertion failed: (isa<X>(Val) && "cast<Ty>() argument of incompatible type!"), function cast, file /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/llvm/include/llvm/Support/Casting.h, line 237.
Abort trap: 6

[mahkoh]

Dup #18358

[nagisa]

Alternatively dup of #19495, though the assertion differs.

[adambirtles]

The different assertion may be an OS thing, this is what I get from playpen:

rustc: /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/llvm/include/llvm/Support/Casting.h:237: typename llvm::cast_retty<X, Y*>::ret_type llvm::cast(Y*) [with X = llvm::Function; Y = llvm::Value; typename llvm::cast_retty<X, Y*>::ret_type = llvm::Function*]: Assertion `isa<X>(Val) && "cast<Ty>() argument of incompatible type!"' failed.
Aborted (core dumped)
playpen: application terminated with error code 134
Program ended.

[adambirtles]

Does anyone know of a workaround for this?

[nagisa]

Do not #[no_mangle] the main. Use #[main] (to define C-like entry) and #[start] (to define barebones entry) attributes instead. Alternatively you can avoid using attributes completely for fn main.

[nagisa]

The sample in the report now results in

test.rs:19:1: 20:2 error: entry symbol `main` defined multiple times
test.rs:19 pub fn main() {
test.rs:20 }
help: did you use #[no_mangle] on `fn main`? Use #[start] instead
error: aborting due to previous error

So this can be closed.