Code that misuses the `write!` macro hangs rustc for 1 minute and then SIGILLs (OOM)

[japaric]

STR

fn main() {
    let mut v = vec![];
    write!(&v, "Hello world");
}

Output

$ time rustc write.rs
<std macros>:3:24: 3:14 error: cannot borrow immutable dereference of `&`-pointer as mutable
<std macros>:3         let dst = &mut *$dst;
[2]    2803 illegal hardware instruction (core dumped)  rustc write.rs
rustc write.rs  58.66s user 4.81s system 99% cpu 1:03.86 total

Backtrace

#0  0x00007ffff7351560 in oom::h6671a0e79ac45df3RTa () from /usr/lib64/librustrt-4e7c5e5c.so
#1  0x00007ffff499c535 in ?? () from /usr/lib64/libsyntax-4e7c5e5c.so
#2  0x00007ffff4a3fd27 in ?? () from /usr/lib64/libsyntax-4e7c5e5c.so
#3  0x00007ffff4a3b083 in diagnostic::EmitterWriter.Emitter::emit::h8944016a574210b0lrG ()
   from /usr/lib64/libsyntax-4e7c5e5c.so
#4  0x00007ffff4a398f9 in diagnostic::Handler::emit::hef6d94e096dac3f1F8F ()
   from /usr/lib64/libsyntax-4e7c5e5c.so
#5  0x00007ffff4a0c3ed in diagnostic::SpanHandler::span_err::he4174115bd82cc5fEWF ()
   from /usr/lib64/libsyntax-4e7c5e5c.so
#6  0x00007ffff5a77fea in middle::borrowck::BorrowckCtxt$LT$$x27a$C$$x20$x27tcx$GT$::report::h3050434306868883rEh () from /usr/lib64/librustc-4e7c5e5c.so
#7  0x00007ffff5a7d524 in middle::borrowck::gather_loans::GatherLoanCtxt$LT$$x27a$C$$x20$x27tcx$GT$.euv..Delegate$LT$$x27tcx$GT$::borrow::hd3a8e951ce2e3945bef () from /usr/lib64/librustc-4e7c5e5c.so
#8  0x00007ffff5a87421 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#9  0x00007ffff5a83d44 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#10 0x00007ffff5a830d0 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#11 0x00007ffff5a838d7 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#12 0x00007ffff5a876a9 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#13 0x00007ffff5a83091 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#14 0x00007ffff5a7ad31 in middle::borrowck::gather_loans::gather_loans_in_fn::ha2f120a3c6b6b70b96e ()
   from /usr/lib64/librustc-4e7c5e5c.so
#15 0x00007ffff5a9c574 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#16 0x00007ffff5a9961d in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#17 0x00007ffff5a9b666 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#18 0x00007ffff5a9a2f8 in ?? () from /usr/lib64/librustc-4e7c5e5c.so
#19 0x00007ffff5a99cc5 in middle::borrowck::check_crate::h7908f5f01a09671eOPg ()
   from /usr/lib64/librustc-4e7c5e5c.so
#20 0x00007ffff76a9917 in ?? () from /usr/lib64/librustc_trans-4e7c5e5c.so
#21 0x00007ffff7840568 in driver::driver::phase_3_run_analysis_passes::he238813c217c3b94efS ()
   from /usr/lib64/librustc_trans-4e7c5e5c.so
#22 0x00007ffff7833238 in driver::driver::compile_input::h117f94c1b348a398YVR ()
   from /usr/lib64/librustc_trans-4e7c5e5c.so
#23 0x00007ffff78b7cd7 in ?? () from /usr/lib64/librustc_trans-4e7c5e5c.so
#24 0x00007ffff78b62fc in ?? () from /usr/lib64/librustc_trans-4e7c5e5c.so
#25 0x00007ffff76c2f78 in ?? () from /usr/lib64/librustc_trans-4e7c5e5c.so
#26 0x00007ffff76c2e83 in ?? () from /usr/lib64/librustc_trans-4e7c5e5c.so
#27 0x00007ffff7bd6be2 in ?? () from /usr/lib64/libnative-4e7c5e5c.so
#28 0x00007ffff7390fec in ?? () from /usr/lib64/librustrt-4e7c5e5c.so
#29 0x00007ffff7390fd6 in rust_try () from /usr/lib64/librustrt-4e7c5e5c.so
#30 0x00007ffff733f843 in unwind::try::h03ead95328113b2fIZc () from /usr/lib64/librustrt-4e7c5e5c.so
#31 0x00007ffff733f70c in task::Task::run::hed7dc0cf620a0172y5b () from /usr/lib64/librustrt-4e7c5e5c.so
#32 0x00007ffff7bd69e7 in ?? () from /usr/lib64/libnative-4e7c5e5c.so
#33 0x00007ffff7340f35 in ?? () from /usr/lib64/librustrt-4e7c5e5c.so
#34 0x00007ffff1e0e294 in start_thread () from /lib64/libpthread.so.0
#35 0x00007ffff70181ed in clone () from /lib64/libc.so.6

Version

1d81776

Can anyone reproduce? I find this bizarre...

cc @alexcrichton @jakub- @sfackler

[barosl]

Same here. The error message is completely different from that of the old compiler.

• 336349c 2014-11-17 20:37:19 +0000:

test.rs:3:12: 3:14 error: type `&collections::vec::Vec<_>` does not implement any method in scope named `write_fmt`
test.rs:3     write!(&v, "Hello world");

• 399ff25 2014-11-20 00:27:07 +0000:

<std macros>:3:24: 3:14 error: cannot borrow immutable dereference of `&`-pointer as mutable
<std macros>:3         let dst = &mut *$dst;

[barosl]

This is a duplicate of #19155, by the way.

[sfackler]

I don't think this is a dup of that. The compiler doesn't OOM in my bug.

[barosl]

Oh, then it is a separate one. To be accurate, my test above also consumed the entire memory and died.

[kmcallister]

Fail to reproduce on Linux with rustc 1.0.0-dev (4e4e8cf 2015-01-24 22:14:14 +0000).

[japaric]

The write! macro has changed since I opened this issue. I sort-of replicated the old write! macro but couldn't reproduce the bug:

macro_rules! mywrite {
    ($dst:expr, $($arg:tt)*) => ({
        let dst = &mut *$dst;  //~ error: cannot borrow immutable borrowed content as mutable
        (|&mut: args| { dst.write_fmt(args) })(format_args!($($arg)*))
    })
}

fn main() {
    let mut v = vec![];
    mywrite!(&v, "Hello world");
}

We should add a test to avoid regressions.

The subtlety with write! is that it's defined in an external crate so a potential test should ideally reflect that. :)

[kmcallister]

Still no hang with

// mywrite.rs
#![crate_type="lib"]

#[macro_export]
macro_rules! mywrite {
    ($dst:expr, $($arg:tt)*) => ({
        let dst = &mut *$dst;  //~ error: cannot borrow immutable borrowed content as mutable
        (|&mut: args| { dst.write_fmt(args) })(format_args!($($arg)*))
    })
}

and

// main.rs
$ cat main.rs
#[macro_use] extern crate mywrite;

fn main() {
    let mut v = vec![];
    mywrite!(&v, "Hello world");
}

Result:

$ rustc --version
rustc 1.0.0-dev (4e4e8cff1 2015-01-24 22:14:14 +0000)

$ rustc -L . mywrite.rs 

$ time rustc -L . main.rs 
<mywrite macros>:3:17: 5:16 error: cannot borrow immutable borrowed content as mutable
<mywrite macros>:3 let dst = & mut * $ dst ; ( | & mut : args | { dst . write_fmt ( args ) } ) (
<mywrite macros>:4 format_args ! ( $ ( $ arg ) * ) ) } )
<mywrite macros>:1:1: 4:38 note: in expansion of mywrite!
main.rs:5:5: 5:33 note: expansion site
error: aborting due to previous error

real    0m0.066s
user    0m0.056s
sys     0m0.008s