Compiler crashes on inline asssembly

[joshlf]

When compiling the following program:

#![feature(asm)]

fn main() {
    unsafe { asm!("callq $0" : : "0"(foo)) };
}

extern "C" {
    fn foo(a: usize);
}

I get the following failure:

thread '<unnamed>' panicked at 'called `Option::unwrap()` on a `None` value', libcore/option.rs:345:21
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
   1: std::sys_common::backtrace::print
   2: std::panicking::default_hook::{{closure}}
   3: std::panicking::default_hook
   4: rustc::util::common::panic_hook
   5: std::panicking::rust_panic_with_hook
   6: std::panicking::continue_panic_fmt
   7: rust_begin_unwind
   8: core::panicking::panic_fmt
   9: core::panicking::panic
  10: rustc_codegen_llvm::llvm::diagnostic::Diagnostic::unpack
  11: rustc_codegen_llvm::back::write::diagnostic_handler
  12: _ZN4llvm17DiagnosticHandler17handleDiagnosticsERKNS_14DiagnosticInfoE
  13: _ZN4llvm11LLVMContext8diagnoseERKNS_14DiagnosticInfoE
  14: _ZN4llvm11LLVMContext9emitErrorEjRKNS_5TwineE
  15: _ZNK4llvm10AsmPrinter13EmitInlineAsmEPKNS_12MachineInstrE
  16: _ZN4llvm10AsmPrinter16EmitFunctionBodyEv
  17: _ZN4llvm13X86AsmPrinter20runOnMachineFunctionERNS_15MachineFunctionE
  18: _ZN4llvm19MachineFunctionPass13runOnFunctionERNS_8FunctionE
  19: _ZN4llvm13FPPassManager13runOnFunctionERNS_8FunctionE
  20: _ZN4llvm13FPPassManager11runOnModuleERNS_6ModuleE
  21: _ZN4llvm6legacy15PassManagerImpl3runERNS_6ModuleE
  22: LLVMRustWriteOutputFile
  23: rustc_codegen_llvm::back::write::write_output_file
  24: rustc_codegen_llvm::back::write::codegen::{{closure}}
  25: rustc::util::common::time_ext
  26: rustc_codegen_llvm::back::write::codegen
  27: rustc_codegen_llvm::back::write::execute_work_item
query stack during panic:
end of query stack
error: aborting due to worker thread failure

error: aborting due to previous error

Playground link

$ rustc --version
rustc 1.30.0-nightly (90d36fb59 2018-09-13)

[paoloteti]

Your asm code is wrong. You need an immediate value or %eax with callq. This is the root-casue and you may experice the same issue with probably any asm (malformed) code. In a sense this is a well-known issue.

[joshlf]

Your asm code is wrong. You need an immediate value or %eax with callq. This is the root-casue and you may experice the same issue with probably any asm (malformed) code. In a sense this is a well-known issue.

I figured it was invalid, but the compiler still shouldn't crash :)

[paoloteti]

Yes! My remarks was "is a well-known issue". So most likely is a duplicate.

[joshlf]

It doesn't look like a duplicate of any of the existing inline assembly ICEs; this is the only issue I've found which manifests as an unwrap on a None value.

[levex]

This will be fixed by #54568, which checks whether the constraints make sense for the inline assembly.

$ rustc +stage1 54376.rs
error[E0668]: malformed inline assembly
 --> 54376.rs:4:14
  |
4 |     unsafe { asm!("callq $0" : : "0"(foo)) };
  |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0668`.

Although, it looks like the error message isn't particularly helpful at this point.

[varkor]

Fixed by #54568.