Today's nightly (stack probes) causes capnpc to segfault

[FauxFaux]

When capnpc is called from a build script, it segfaults. This did not happen on yesterday's nightly. It doesn't seem to happen outside of build scripts. I don't get why that would be.

Testcase: https://github.com/FauxFaux/capnpc-segfault

You need capnp on your path (although it's irrelevant); apt install capnproto on recent Debian/Ubuntu.

% rustup run nightly-2017-07-06 cargo build
    Finished dev [unoptimized + debuginfo] target(s) in 0.0 secs

% rustup run nightly cargo build 
   Compiling capnpc-segfault v0.1.0 (fi...t)
error: failed to run custom build command for `capnpc-segfault v0.1.0 (fi..t)`
process didn't exit successfully: `...lt/target/debug/build/c...4a/build-script-build` (signal: 11, SIGSEGV: invalid memory reference)

% rustup run nightly rustc --version
rustc 1.20.0-nightly (696412de7 2017-07-06)

% OUT_DIR=/tmp RUST_BACKTRACE=1 rust-gdb --args target/debug/build/*/build-script-build /tmp
...
(gdb) bt
#0  0x000055555567f8ec in compiler_builtins::probestack::__rust_probestack () at /checkout/src/rustc/compiler_builtins_shim/../../libcompiler_builtins/src/probestack.rs:55
#1  0x00005555555f0e31 in capnpc::codegen::generate_node (gen=0x0, node_id=0, node_name="", parent_node_id=core::option::Option::None) at /home/faux/.cargo/registry/src/github.com-1ecc6299db9ec823/capnpc-0.8.5/src/codegen.rs:1014
#2  0x00005555555f166d in capnpc::codegen::generate_node (gen=0x7fffffffc3f0, node_id=12947750709585725918, node_name="entry", parent_node_id=core::option::Option::None)
    at /home/faux/.cargo/registry/src/github.com-1ecc6299db9ec823/capnpc-0.8.5/src/codegen.rs:1030
#3  0x0000555555617988 in capnpc::codegen::main<std::process::ChildStdout> (inp=ChildStdout = {...}, out_dir=0x7ffff6c20038) at /home/faux/.cargo/registry/src/github.com-1ecc6299db9ec823/capnpc-0.8.5/src/codegen.rs:1846
#4  0x0000555555624b44 in capnpc::run_command (command=Command = {...}) at /home/faux/.cargo/registry/src/github.com-1ecc6299db9ec823/capnpc-0.8.5/src/lib.rs:76
#5  0x0000555555625849 in capnpc::CompilerCommand::run (self=0x7fffffffde30) at /home/faux/.cargo/registry/src/github.com-1ecc6299db9ec823/capnpc-0.8.5/src/lib.rs:162
#6  0x0000555555566831 in build_script_build::main () at build.rs:4

The faulting code looks pretty innocent, and we're only two frames down the recursion?

https://github.com/capnproto/capnpc-rust/blob/e775eec5af5eea77e8ed4919a647fab9fc877343/src/codegen.rs#L1019

Presumably related to 5dbd97d / #43052.

Happens on this machine:

• Ubuntu Zesty (17.04); 4.10.0-26-generic #30-Ubuntu amd64, i7 Ivy-Bridge, 24GB RAM.

But not on:

• Ubuntu Trusty (16.04); 4.4.0-79-generic #100-Ubuntu, amd64, E3-1 Xeon, 16GB RAM.

...presumably because the second machine has not been rebooted to pick up the stack guard fixes.

[est31]

I've got a similar issue, see #43102

[alexcrichton]

Ah yes I believe this is the same as #43102 so I'm going to close in favor of that, but thanks for the report @FauxFaux!