Auto merge of #111769 - saethlin:ctfe-backtrace-ctrlc, r=RalfJung

Print a backtrace in const eval if interrupted

Demo:
```rust
#![feature(const_eval_limit)]
#![const_eval_limit = "0"]

const OW: u64 = {
    let mut res: u64 = 0;
    let mut i = 0;
    while i < u64::MAX {
        res = res.wrapping_add(i);
        i += 1;
    }
    res
};

fn main() {
    println!("{}", OW);
}
```
```
╭ ➜ ben@archlinux:~/rust
╰ ➤ rustc +stage1 spin.rs
^Cerror[E0080]: evaluation of constant value failed
 --> spin.rs:8:33
  |
8 |         res = res.wrapping_add(i);
  |                                 ^ Compilation was interrupted

note: erroneous constant used
  --> spin.rs:15:20
   |
15 |     println!("{}", OW);
   |                    ^^

note: erroneous constant used
  --> spin.rs:15:20
   |
15 |     println!("{}", OW);
   |                    ^^
   |
   = note: this note originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (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 E0080`.
```

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -1,3 +1,5 @@
+use std::sync::atomic::Ordering::Relaxed;
+
 use either::{Left, Right};
 
 use rustc_hir::def::DefKind;
@@ -22,6 +24,7 @@ use crate::interpret::{
     InternKind, InterpCx, InterpError, InterpResult, MPlaceTy, MemoryKind, OpTy, RefTracking,
     StackPopCleanup,
 };
+use crate::CTRL_C_RECEIVED;
 
 // Returns a pointer to where the result lives
 #[instrument(level = "trace", skip(ecx, body))]
@@ -79,7 +82,11 @@ fn eval_body_using_ecx<'mir, 'tcx, R: InterpretationResult<'tcx>>(
     ecx.storage_live_for_always_live_locals()?;
 
     // The main interpreter loop.
-    while ecx.step()? {}
+    while ecx.step()? {
+        if CTRL_C_RECEIVED.load(Relaxed) {
+            throw_exhaust!(Interrupted);
+        }
+    }
 
     // Intern the result
     intern_const_alloc_recursive(ecx, intern_kind, &ret)?;

compiler/rustc_const_eval/src/errors.rs

@@ -884,6 +884,7 @@ impl ReportErrorExt for ResourceExhaustionInfo {
             ResourceExhaustionInfo::StackFrameLimitReached => const_eval_stack_frame_limit_reached,
             ResourceExhaustionInfo::MemoryExhausted => const_eval_memory_exhausted,
             ResourceExhaustionInfo::AddressSpaceFull => const_eval_address_space_full,
+            ResourceExhaustionInfo::Interrupted => const_eval_interrupted,
         }
     }
     fn add_args<G: EmissionGuarantee>(self, _: &mut Diag<'_, G>) {}

compiler/rustc_const_eval/src/lib.rs

@@ -32,6 +32,8 @@ pub mod interpret;
 pub mod transform;
 pub mod util;
 
+use std::sync::atomic::AtomicBool;
+
 pub use errors::ReportErrorExt;
 
 use rustc_middle::{ty, util::Providers};
@@ -58,3 +60,8 @@ pub fn provide(providers: &mut Providers) {
         util::check_validity_requirement(tcx, init_kind, param_env_and_ty)
     };
 }
+
+/// `rustc_driver::main` installs a handler that will set this to `true` if
+/// the compiler has been sent a request to shut down, such as by a Ctrl-C.
+/// This static lives here because it is only read by the interpreter.
+pub static CTRL_C_RECEIVED: AtomicBool = AtomicBool::new(false);