implement exit

implement exit code via new error kind

rust-version

@@ -1 +1 @@
-130dc3e7dac132cf30272ccf4541b512828e2108
+9224be5fa39f6170f6e046342976efee5453a1ff

src/fn_call.rs

@@ -69,11 +69,15 @@ pub trait EvalContextExt<'a, 'mir, 'tcx: 'a + 'mir>: crate::MiriEvalContextExt<'
         let link_name = link_name.get().trim_end_matches("$UNIX2003");
         let tcx = &{this.tcx.tcx};
 
-        // First: functions that could diverge.
+        // First: functions that diverge.
         match link_name {
             "__rust_start_panic" | "panic_impl" => {
                 return err!(MachineError("the evaluated program panicked".to_string()));
             }
+            "exit" => {
+                let code = this.read_scalar(args[0])?.to_i32()?;
+                return err!(Exit(code));
+            }
             _ => if dest.is_none() {
                 return err!(Unimplemented(
                     format!("can't call diverging foreign function: {}", link_name),

src/lib.rs

@@ -242,6 +242,13 @@ pub fn eval_main<'a, 'tcx: 'a>(
             }
         }
         Err(mut e) => {
+            // Special treatment for some error kinds
+            let msg = match e.kind {
+                InterpError::Exit(code) => std::process::exit(code),
+                InterpError::NoMirFor(..) =>
+                    format!("{}. Did you set `MIRI_SYSROOT` to a Miri-enabled sysroot? You can prepare one with `cargo miri setup`.", e),
+                _ => e.to_string()
+            };
             e.print_backtrace();
             if let Some(frame) = ecx.stack().last() {
                 let block = &frame.mir.basic_blocks()[frame.block];
@@ -251,11 +258,10 @@ pub fn eval_main<'a, 'tcx: 'a>(
                     block.terminator().source_info.span
                 };
 
-                let e = e.to_string();
-                let msg = format!("constant evaluation error: {}", e);
+                let msg = format!("Miri evaluation error: {}", msg);
                 let mut err = struct_error(ecx.tcx.tcx.at(span), msg.as_str());
                 let frames = ecx.generate_stacktrace(None);
-                err.span_label(span, e);
+                err.span_label(span, msg);
                 // We iterate with indices because we need to look at the next frame (the caller).
                 for idx in 0..frames.len() {
                     let frame_info = &frames[idx];
@@ -269,7 +275,7 @@ pub fn eval_main<'a, 'tcx: 'a>(
                 }
                 err.emit();
             } else {
-                ecx.tcx.sess.err(&e.to_string());
+                ecx.tcx.sess.err(&msg);
             }
 
             for (i, frame) in ecx.stack().iter().enumerate() {

tests/run-pass/exit.rs

@@ -0,0 +1,3 @@
+fn main() {
+    std::process::exit(0)
+}