Avoid creating a second UnwindContext in finalize_definitions

Once UnwindContext sets the personality function it will need to define
a DW.ref.rust_eh_personality function which would cause a duplicate
definition if UnwindContext is called a second time.

Author: bjorn3

src/driver/jit.rs

@@ -84,7 +84,7 @@ pub(crate) fn run_jit(tcx: TyCtxt<'_>, jit_args: Vec<String>) -> ! {
 
     tcx.dcx().abort_if_errors();
 
-    jit_module.finalize_definitions();
+    let mut jit_module = jit_module.finalize_definitions();
 
     println!(
         "Rustc codegen cranelift will JIT run the executable, because -Cllvm-args=mode=jit was passed"
@@ -104,7 +104,7 @@ pub(crate) fn run_jit(tcx: TyCtxt<'_>, jit_args: Vec<String>) -> ! {
         call_conv: jit_module.target_config().default_call_conv,
     };
     let start_func_id = jit_module.declare_function("main", Linkage::Import, &start_sig).unwrap();
-    let finalized_start: *const u8 = jit_module.module.get_finalized_function(start_func_id);
+    let finalized_start: *const u8 = jit_module.get_finalized_function(start_func_id);
 
     let f: extern "C" fn(c_int, *const *const c_char) -> c_int =
         unsafe { ::std::mem::transmute(finalized_start) };

src/unwind_module.rs

@@ -33,13 +33,10 @@ impl UnwindModule<ObjectModule> {
 
 #[cfg(feature = "jit")]
 impl UnwindModule<cranelift_jit::JITModule> {
-    pub(crate) fn finalize_definitions(&mut self) {
+    pub(crate) fn finalize_definitions(mut self) -> cranelift_jit::JITModule {
         self.module.finalize_definitions().unwrap();
-        let prev_unwind_context = std::mem::replace(
-            &mut self.unwind_context,
-            UnwindContext::new(&mut self.module, false),
-        );
-        unsafe { prev_unwind_context.register_jit(&self.module) };
+        unsafe { self.unwind_context.register_jit(&self.module) };
+        self.module
     }
 }