Print message when reaching trap

src/abi.rs

@@ -590,7 +590,7 @@ pub fn codegen_terminator_call<'a, 'tcx: 'a>(
         let ret_ebb = fx.get_ebb(dest);
         fx.bcx.ins().jump(ret_ebb, &[]);
     } else {
-        trap_unreachable(&mut fx.bcx);
+        trap_unreachable(fx, "[corruption] Diverging function returned");
     }
 }
 

src/base.rs

@@ -108,9 +108,28 @@ fn trans_fn<'a, 'clif, 'tcx: 'a, B: Backend + 'static>(
             let start_ebb = bcx.create_ebb();
             bcx.append_ebb_params_for_function_params(start_ebb);
             bcx.switch_to_block(start_ebb);
-            crate::trap::trap_unreachable(&mut bcx);
+
-            bcx.seal_all_blocks();
+            let mut fx = FunctionCx {
-            bcx.finalize();
+                tcx,
+                module: cx.module,
+                pointer_type: pointer_ty(tcx),
+
+                instance,
+                mir,
+
+                bcx,
+                ebb_map: HashMap::new(),
+                local_map: HashMap::new(),
+
+                clif_comments: crate::pretty_clif::CommentWriter::new(tcx, instance),
+                constants: &mut cx.ccx,
+                caches: &mut cx.caches,
+                source_info_set: indexmap::IndexSet::new(),
+            };
+
+            crate::trap::trap_unreachable(&mut fx, "[unimplemented] Called function with u128 or i128 as argument.");
+            fx.bcx.seal_all_blocks();
+            fx.bcx.finalize();
 
             // Step 2b3. Define function
             cx.caches.context.func = func;
@@ -254,7 +273,7 @@ fn codegen_fn_content<'a, 'tcx: 'a>(fx: &mut FunctionCx<'a, 'tcx, impl Backend>)
             TerminatorKind::Assert {
                 cond,
                 expected,
-                msg: _,
+                msg,
                 target,
                 cleanup: _,
             } => {
@@ -267,7 +286,7 @@ fn codegen_fn_content<'a, 'tcx: 'a>(fx: &mut FunctionCx<'a, 'tcx, impl Backend>)
                 } else {
                     fx.bcx.ins().brz(cond, target, &[]);
                 };
-                trap_panic(&mut fx.bcx);
+                trap_panic(fx, format!("[panic] Assert {:?} failed.", msg));
             }
 
             TerminatorKind::SwitchInt {
@@ -294,8 +313,11 @@ fn codegen_fn_content<'a, 'tcx: 'a>(fx: &mut FunctionCx<'a, 'tcx, impl Backend>)
             } => {
                 crate::abi::codegen_terminator_call(fx, func, args, destination);
             }
-            TerminatorKind::Resume | TerminatorKind::Abort | TerminatorKind::Unreachable => {
+            TerminatorKind::Resume | TerminatorKind::Abort => {
-                trap_unreachable(&mut fx.bcx);
+                trap_unreachable(fx, "[corruption] Unwinding bb reached.");
+            }
+            TerminatorKind::Unreachable => {
+                trap_unreachable(fx, "[corruption] Hit unreachable code.");
             }
             TerminatorKind::Yield { .. }
             | TerminatorKind::FalseEdges { .. }
@@ -742,7 +764,7 @@ pub fn trans_get_discriminant<'a, 'tcx: 'a>(
     let layout = place.layout();
 
     if layout.abi == layout::Abi::Uninhabited {
-        return trap_unreachable_ret_value(fx, dest_layout);
+        return trap_unreachable_ret_value(fx, dest_layout, "[panic] Tried to get discriminant for uninhabited type.");
     }
 
     let (discr_scalar, discr_kind) = match &layout.variants {

src/constant.rs

@@ -69,7 +69,13 @@ pub fn trans_promoted<'a, 'tcx: 'a>(
             debug_assert_eq!(cplace.layout(), fx.layout_of(dest_ty));
             cplace
         }
-        Err(_) => crate::trap::trap_unreachable_ret_place(fx, fx.layout_of(dest_ty)),
+        Err(_) => {
+            crate::trap::trap_unreachable_ret_place(
+                fx,
+                fx.layout_of(dest_ty),
+                "[panic] Tried to get value of promoted value with errored during const eval.",
+            )
+        }
     }
 }
 

src/intrinsics.rs

@@ -103,10 +103,10 @@ pub fn codegen_intrinsic_call<'a, 'tcx: 'a>(
             // Insert non returning intrinsics here
             match intrinsic {
                 "abort" => {
-                    trap_panic(&mut fx.bcx);
+                    trap_panic(fx, "Called intrinisc::abort.");
                 }
                 "unreachable" => {
-                    trap_unreachable(&mut fx.bcx);
+                    trap_unreachable(fx, "[corruption] Called intrinsic::unreachable.");
                 }
                 _ => unimplemented!("unsupported instrinsic {}", intrinsic),
             }
@@ -339,7 +339,7 @@ pub fn codegen_intrinsic_call<'a, 'tcx: 'a>(
         };
         init, () {
             if ret.layout().abi == Abi::Uninhabited {
-                crate::trap::trap_panic(&mut fx.bcx);
+                crate::trap::trap_panic(fx, "[panic] Called intrinsic::init for uninhabited type.");
                 return;
             }
 
@@ -377,7 +377,7 @@ pub fn codegen_intrinsic_call<'a, 'tcx: 'a>(
         };
         uninit, <T> () {
             if ret.layout().abi == Abi::Uninhabited {
-                crate::trap::trap_panic(&mut fx.bcx);
+                crate::trap::trap_panic(fx, "[panic] Called intrinsic::uninit for uninhabited type.");
                 return;
             }
 
@@ -412,7 +412,7 @@ pub fn codegen_intrinsic_call<'a, 'tcx: 'a>(
         };
         panic_if_uninhabited, <T> () {
             if fx.layout_of(T).abi.is_uninhabited() {
-                crate::trap::trap_panic(&mut fx.bcx);
+                crate::trap::trap_panic(fx, "[panic] Called intrinsic::panic_if_uninhabited for uninhabited type.");
                 return;
             }
         };
@@ -492,6 +492,6 @@ pub fn codegen_intrinsic_call<'a, 'tcx: 'a>(
         let ret_ebb = fx.get_ebb(dest);
         fx.bcx.ins().jump(ret_ebb, &[]);
     } else {
-        trap_unreachable(&mut fx.bcx);
+        trap_unreachable(fx, "[corruption] Diverging intrinsic returned.");
     }
 }

src/trap.rs

@@ -1,23 +1,51 @@
 use crate::prelude::*;
 
+fn codegen_print(fx: &mut FunctionCx<'_, '_, impl cranelift_module::Backend>, msg: &str) {
+    let puts = fx.module.declare_function("puts", Linkage::Import, &Signature {
+        call_conv: CallConv::SystemV,
+        params: vec![AbiParam::new(pointer_ty(fx.tcx))],
+        returns: vec![],
+    }).unwrap();
+    let puts = fx.module.declare_func_in_func(puts, &mut fx.bcx.func);
+
+    let symbol_name = fx.tcx.symbol_name(fx.instance);
+    let msg_bytes = format!("trap at {:?} ({}): {}\0", fx.instance, symbol_name, msg).into_bytes().into_boxed_slice();
+    let mut data_ctx = DataContext::new();
+    data_ctx.define(msg_bytes);
+    let msg_id = fx.module.declare_data(&(symbol_name.as_str().to_string() + msg), Linkage::Local, false).unwrap();
+
+    // Ignore DuplicateDefinition error, as the data will be the same
+    let _ = fx.module.define_data(msg_id, &data_ctx);
+
+    let local_msg_id = fx.module.declare_data_in_func(msg_id, fx.bcx.func);
+    let msg_ptr = fx.bcx.ins().global_value(pointer_ty(fx.tcx), local_msg_id);
+    fx.bcx.ins().call(puts, &[msg_ptr]);
+}
+
 /// Trap code: user0
-pub fn trap_panic(bcx: &mut FunctionBuilder) {
+pub fn trap_panic(fx: &mut FunctionCx<'_, '_, impl cranelift_module::Backend>, msg: impl AsRef<str>) {
-    bcx.ins().trap(TrapCode::User(0));
+    codegen_print(fx, msg.as_ref());
+    fx.bcx.ins().trap(TrapCode::User(0));
 }
 
 /// Trap code: user65535
-pub fn trap_unreachable(bcx: &mut FunctionBuilder) {
+pub fn trap_unreachable(fx: &mut FunctionCx<'_, '_, impl cranelift_module::Backend>, msg: impl AsRef<str>) {
-    bcx.ins().trap(TrapCode::User(!0));
+    codegen_print(fx, msg.as_ref());
+    fx.bcx.ins().trap(TrapCode::User(!0));
 }
 
-pub fn trap_unreachable_ret_value<'tcx>(fx: &mut FunctionCx<'_, 'tcx, impl cranelift_module::Backend>, dest_layout: TyLayout<'tcx>) -> CValue<'tcx> {
+/// Trap code: user65535
+pub fn trap_unreachable_ret_value<'tcx>(fx: &mut FunctionCx<'_, 'tcx, impl cranelift_module::Backend>, dest_layout: TyLayout<'tcx>, msg: impl AsRef<str>) -> CValue<'tcx> {
+    codegen_print(fx, msg.as_ref());
     let true_ = fx.bcx.ins().iconst(types::I32, 1);
     fx.bcx.ins().trapnz(true_, TrapCode::User(!0));
     let zero = fx.bcx.ins().iconst(fx.pointer_type, 0);
     CValue::ByRef(zero, dest_layout)
 }
 
-pub fn trap_unreachable_ret_place<'tcx>(fx: &mut FunctionCx<'_, 'tcx, impl cranelift_module::Backend>, dest_layout: TyLayout<'tcx>) -> CPlace<'tcx> {
+/// Trap code: user65535
+pub fn trap_unreachable_ret_place<'tcx>(fx: &mut FunctionCx<'_, 'tcx, impl cranelift_module::Backend>, dest_layout: TyLayout<'tcx>, msg: impl AsRef<str>) -> CPlace<'tcx> {
+    codegen_print(fx, msg.as_ref());
     let true_ = fx.bcx.ins().iconst(types::I32, 1);
     fx.bcx.ins().trapnz(true_, TrapCode::User(!0));
     let zero = fx.bcx.ins().iconst(fx.pointer_type, 0);