Add test and fix parsing/gating

Author: saethlin

src/cargo/core/compiler/mod.rs

@@ -1234,6 +1234,9 @@ fn build_base_args(
     if *panic != PanicStrategy::Unwind {
         cmd.arg("-C").arg(format!("panic={}", panic));
     }
+    if *panic == PanicStrategy::ImmediateAbort {
+        cmd.arg("-Z").arg("unstable-options");
+    }
 
     cmd.args(&lto_args(build_runner, unit));
 

src/cargo/core/features.rs

@@ -890,6 +890,7 @@ unstable_cli_options!(
     skip_rustdoc_fingerprint: bool,
     target_applies_to_host: bool = ("Enable the `target-applies-to-host` key in the .cargo/config.toml file"),
     trim_paths: bool = ("Enable the `trim-paths` option in profiles"),
+    panic_immediate_abort: bool = ("Enable setting `panic = \"immediate-abort\"` in profiles"),
     unstable_options: bool = ("Allow the usage of unstable options"),
     warnings: bool = ("Allow use of the build.warnings config key"),
 );
@@ -1420,6 +1421,7 @@ impl CliUnstable {
             "skip-rustdoc-fingerprint" => self.skip_rustdoc_fingerprint = parse_empty(k, v)?,
             "script" => self.script = parse_empty(k, v)?,
             "target-applies-to-host" => self.target_applies_to_host = parse_empty(k, v)?,
+            "panic-immediate-abort" => self.panic_immediate_abort = parse_empty(k, v)?,
             "unstable-options" => self.unstable_options = parse_empty(k, v)?,
             "warnings" => self.warnings = parse_empty(k, v)?,
             _ => bail!(

src/cargo/util/toml/mod.rs

@@ -2550,10 +2550,10 @@ pub fn validate_profile(
     }
 
     if let Some(panic) = &root.panic {
-        if panic != "unwind" && panic != "abort" {
+        if panic != "unwind" && panic != "abort" && panic != "immediate-abort" {
             bail!(
                 "`panic` setting of `{}` is not a valid setting, \
-                     must be `unwind` or `abort`",
+                     must be `unwind`, `abort`, or `immediate-abort`.",
                 panic
             );
         }
@@ -2607,6 +2607,15 @@ fn validate_profile_layer(
             _ => {}
         }
     }
+    if profile.panic.as_deref() == Some("immediate-abort") {
+        match (
+            features.require(Feature::panic_immediate_abort()),
+            cli_unstable.panic_immediate_abort,
+        ) {
+            (Err(e), false) => return Err(e),
+            _ => {}
+        }
+    }
     Ok(())
 }
 

tests/testsuite/main.rs

@@ -150,6 +150,7 @@ mod proc_macro;
 mod profile_config;
 mod profile_custom;
 mod profile_overrides;
+mod profile_panic_immediate_abort;
 mod profile_targets;
 mod profile_trim_paths;
 mod profiles;