Put checks that detect UB under their own flag below debug_assertions

3 files changed, 13 insertions, 0 deletions

diff --git a/compiler/rustc_session/src/config/cfg.rs b/compiler/rustc_session/src/config/cfg.rs
index 337019f720b..34dcd0cf598 100644
--- a/compiler/rustc_session/src/config/cfg.rs
+++ b/compiler/rustc_session/src/config/cfg.rs
@@ -212,6 +212,10 @@ pub(crate) fn default_configuration(sess: &Session) -> Cfg {
         ins_none!(sym::test);
     }
 
+    if sess.ub_checks() {
+        ins_none!(sym::ub_checks);
+    }
+
     ret
 }
 
@@ -367,6 +371,8 @@ impl CheckCfg {
 
         ins!(sym::test, no_values);
 
+        ins!(sym::ub_checks, no_values);
+
         ins!(sym::unix, no_values);
         ins!(sym::windows, no_values);
     }
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index a76eb6b06aa..5e7c2465097 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -1992,6 +1992,9 @@ written to standard error output)"),
         "in diagnostics, use heuristics to shorten paths referring to items"),
     tune_cpu: Option<String> = (None, parse_opt_string, [TRACKED],
         "select processor to schedule for (`rustc --print target-cpus` for details)"),
+    #[rustc_lint_opt_deny_field_access("use `Session::ub_checks` instead of this field")]
+    ub_checks: Option<bool> = (None, parse_opt_bool, [TRACKED],
+        "emit runtime checks for Undefined Behavior (default: -Cdebug-assertions)"),
     ui_testing: bool = (false, parse_bool, [UNTRACKED],
         "emit compiler diagnostics in a form suitable for UI testing (default: no)"),
     uninit_const_chunk_threshold: usize = (16, parse_number, [TRACKED],
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 55fff4421ae..22ca8a3cf3e 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -735,6 +735,10 @@ impl Session {
         self.opts.cg.overflow_checks.unwrap_or(self.opts.debug_assertions)
     }
 
+    pub fn ub_checks(&self) -> bool {
+        self.opts.unstable_opts.ub_checks.unwrap_or(self.opts.debug_assertions)
+    }
+
     pub fn relocation_model(&self) -> RelocModel {
         self.opts.cg.relocation_model.unwrap_or(self.target.relocation_model)
     }