Failing to build on nightly

[nelhage]

I'm getting build errors on Rust nightly, using this minimal test case:

[nelhage@monolithique:/tmp/probetest]$ cargo +nightly build
   Compiling probetest v0.1.0 (/tmp/probetest)
error[E0660]: malformed inline assembly
 --> main.rs:4:5
  |
4 |     probe!(test_probe, entry);
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

warning: use of deprecated item 'asm': the syntax of asm! will change soon, use llvm_asm! to avoid breakage
 --> main.rs:4:5
  |
4 |     probe!(test_probe, entry);
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(deprecated)]` on by default
  = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to previous error; 1 warning emitted

For more information about this error, try `rustc --explain E0660`.
error: could not compile `probetest`.

To learn more, run the command again with --verbose.

I'm seeing this error on a nightly pulled from rustup just now, as well as on nightly-2020-04-08-x86_64-unknown-linux-gnu, although that doesn't give the warning:

[nelhage@monolithique:/tmp/probetest]$ cargo +nightly-2020-04-08-x86_64-unknown-linux-gnu build
   Compiling probetest v0.1.0 (/tmp/probetest)
error[E0660]: malformed inline assembly
 --> main.rs:4:5
  |
4 |     probe!(test_probe, entry);
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to previous error

For more information about this error, try `rustc --explain E0660`.
error: could not compile `probetest`.

To learn more, run the command again with --verbose.

[cuviper]

Rust is transitioning from the old asm! syntax (now llvm_asm! -- rust-lang/rust#70173) to a new syntax (rust-lang/rust#72016), and I converted to the new in probe 0.2. I doubt that will work on a nightly as old as 2020-04-08, but I don't know why it wouldn't work when you pulled a current nightly. Your reproducer works for me with:

rustc 1.45.0-nightly (f93bb2a50 2020-05-25)
binary: rustc
commit-hash: f93bb2a50b37bc8bafe4d960e2afd839eaa854ed
commit-date: 2020-05-25
host: x86_64-unknown-linux-gnu
release: 1.45.0-nightly
LLVM version: 10.0

[cuviper]

FWIW, I could publish a 0.1 update to use llvm_asm! if necessary, but I'm not sure it's needed. There is one downside to the new asm in that it only supports register constraints, which means I had to use isize for arguments instead of i64, since 32-bit platforms can't generally put i64 in registers. Previously, those could be stored as memory operands.

[nelhage]

Ah, darn, my bad -- I ran a rustup update but that seems to have actually gotten a two-week-old build because of some issue related to rls-preview and rustfmt. Grabbing the actual latest nightly fixes it. Sorry for the noise!