give extra context to ABI mismatch errors

compiler/rustc_const_eval/src/errors.rs

@@ -482,6 +482,9 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> {
         use UndefinedBehaviorInfo::*;
         match self {
             Ub(msg) => msg.clone().into(),
+            Custom(x) => (x.msg)(),
+            ValidationError(e) => e.diagnostic_message(),
+
             Unreachable => const_eval_unreachable,
             BoundsCheckFailed { .. } => const_eval_bounds_check_failed,
             DivisionByZero => const_eval_division_by_zero,
@@ -513,8 +516,8 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> {
             ScalarSizeMismatch(_) => const_eval_scalar_size_mismatch,
             UninhabitedEnumVariantWritten(_) => const_eval_uninhabited_enum_variant_written,
             UninhabitedEnumVariantRead(_) => const_eval_uninhabited_enum_variant_read,
-            ValidationError(e) => e.diagnostic_message(),
-            Custom(x) => (x.msg)(),
+            AbiMismatchArgument { .. } => const_eval_incompatible_types,
+            AbiMismatchReturn { .. } => const_eval_incompatible_return_types,
         }
     }
 
@@ -525,8 +528,15 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> {
     ) {
         use UndefinedBehaviorInfo::*;
         match self {
-            Ub(_)
-            | Unreachable
+            Ub(_) => {}
+            Custom(custom) => {
+                (custom.add_args)(&mut |name, value| {
+                    builder.set_arg(name, value);
+                });
+            }
+            ValidationError(e) => e.add_args(handler, builder),
+
+            Unreachable
             | DivisionByZero
             | RemainderByZero
             | DivisionOverflow
@@ -593,11 +603,10 @@ impl<'a> ReportErrorExt for UndefinedBehaviorInfo<'a> {
                 builder.set_arg("target_size", info.target_size);
                 builder.set_arg("data_size", info.data_size);
             }
-            ValidationError(e) => e.add_args(handler, builder),
-            Custom(custom) => {
-                (custom.add_args)(&mut |name, value| {
-                    builder.set_arg(name, value);
-                });
+            AbiMismatchArgument { caller_ty, callee_ty }
+            | AbiMismatchReturn { caller_ty, callee_ty } => {
+                builder.set_arg("caller_ty", caller_ty.to_string());
+                builder.set_arg("callee_ty", callee_ty.to_string());
             }
         }
     }

compiler/rustc_const_eval/src/interpret/terminator.rs

@@ -439,13 +439,10 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
         // Check compatibility
         if !self.check_argument_compat(caller_abi, callee_abi)? {
-            let callee_ty = format!("{}", callee_ty);
-            let caller_ty = format!("{}", caller_arg.layout().ty);
-            throw_ub_custom!(
-                fluent::const_eval_incompatible_types,
-                callee_ty = callee_ty,
-                caller_ty = caller_ty,
-            )
+            throw_ub!(AbiMismatchArgument {
+                caller_ty: caller_abi.layout.ty,
+                callee_ty: callee_abi.layout.ty
+            });
         }
         // We work with a copy of the argument for now; if this is in-place argument passing, we
         // will later protect the source it comes from. This means the callee cannot observe if we
@@ -712,13 +709,10 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     }
                     // Don't forget to check the return type!
                     if !self.check_argument_compat(&caller_fn_abi.ret, &callee_fn_abi.ret)? {
-                        let callee_ty = format!("{}", callee_fn_abi.ret.layout.ty);
-                        let caller_ty = format!("{}", caller_fn_abi.ret.layout.ty);
-                        throw_ub_custom!(
-                            fluent::const_eval_incompatible_return_types,
-                            callee_ty = callee_ty,
-                            caller_ty = caller_ty,
-                        )
+                        throw_ub!(AbiMismatchReturn {
+                            caller_ty: caller_fn_abi.ret.layout.ty,
+                            callee_ty: callee_fn_abi.ret.layout.ty
+                        });
                     }
                     // Ensure the return place is aligned and dereferenceable, and protect it for
                     // in-place return value passing.

compiler/rustc_middle/src/mir/interpret/error.rs

@@ -255,9 +255,16 @@ impl_into_diagnostic_arg_through_debug! {
 
 /// Error information for when the program caused Undefined Behavior.
 #[derive(Debug)]
-pub enum UndefinedBehaviorInfo<'a> {
+pub enum UndefinedBehaviorInfo<'tcx> {
     /// Free-form case. Only for errors that are never caught! Used by miri
     Ub(String),
+    // FIXME(fee1-dead) these should all be actual variants of the enum instead of dynamically
+    // dispatched
+    /// A custom (free-form) fluent-translated error, created by `err_ub_custom!`.
+    Custom(crate::error::CustomSubdiagnostic<'tcx>),
+    /// Validation error.
+    ValidationError(ValidationErrorInfo<'tcx>),
+
     /// Unreachable code was executed.
     Unreachable,
     /// A slice/array index projection went out-of-bounds.
@@ -319,12 +326,10 @@ pub enum UndefinedBehaviorInfo<'a> {
     UninhabitedEnumVariantWritten(VariantIdx),
     /// An uninhabited enum variant is projected.
     UninhabitedEnumVariantRead(VariantIdx),
-    /// Validation error.
-    ValidationError(ValidationErrorInfo<'a>),
-    // FIXME(fee1-dead) these should all be actual variants of the enum instead of dynamically
-    // dispatched
-    /// A custom (free-form) error, created by `err_ub_custom!`.
-    Custom(crate::error::CustomSubdiagnostic<'a>),
+    /// ABI-incompatible argument types.
+    AbiMismatchArgument { caller_ty: Ty<'tcx>, callee_ty: Ty<'tcx> },
+    /// ABI-incompatible return types.
+    AbiMismatchReturn { caller_ty: Ty<'tcx>, callee_ty: Ty<'tcx> },
 }
 
 #[derive(Debug, Clone, Copy)]

src/tools/miri/src/diagnostics.rs

@@ -199,6 +199,7 @@ pub fn report_error<'tcx, 'mir>(
     e: InterpErrorInfo<'tcx>,
 ) -> Option<(i64, bool)> {
     use InterpError::*;
+    use UndefinedBehaviorInfo::*;
 
     let mut msg = vec![];
 
@@ -271,7 +272,7 @@ pub fn report_error<'tcx, 'mir>(
         (title, helps)
     } else {
         let title = match e.kind() {
-            UndefinedBehavior(UndefinedBehaviorInfo::ValidationError(validation_err))
+            UndefinedBehavior(ValidationError(validation_err))
                 if matches!(
                     validation_err.kind,
                     ValidationErrorKind::PointerAsInt { .. } | ValidationErrorKind::PartialPointer
@@ -299,7 +300,7 @@ pub fn report_error<'tcx, 'mir>(
         let helps = match e.kind() {
             Unsupported(_) =>
                 vec![(None, format!("this is likely not a bug in the program; it indicates that the program performed an operation that the interpreter does not support"))],
-            UndefinedBehavior(UndefinedBehaviorInfo::AlignmentCheckFailed { .. })
+            UndefinedBehavior(AlignmentCheckFailed { .. })
                 if ecx.machine.check_alignment == AlignmentCheck::Symbolic
             =>
                 vec![
@@ -311,7 +312,8 @@ pub fn report_error<'tcx, 'mir>(
                     (None, format!("this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior")),
                     (None, format!("see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information")),
                 ];
-                if let UndefinedBehaviorInfo::PointerUseAfterFree(alloc_id, _) | UndefinedBehaviorInfo::PointerOutOfBounds { alloc_id, .. } = info {
+                match info {
+                    PointerUseAfterFree(alloc_id, _) | PointerOutOfBounds { alloc_id, .. } => {
                         if let Some(span) = ecx.machine.allocated_span(*alloc_id) {
                             helps.push((Some(span), format!("{:?} was allocated here:", alloc_id)));
                         }
@@ -319,6 +321,12 @@ pub fn report_error<'tcx, 'mir>(
                             helps.push((Some(span), format!("{:?} was deallocated here:", alloc_id)));
                         }
                     }
+                    AbiMismatchArgument { .. } | AbiMismatchReturn { .. } => {
+                        helps.push((None, format!("this means these two types are not *guaranteed* to be ABI-compatible across all targets")));
+                        helps.push((None, format!("if you think this code should be accepted anyway, please report an issue")));
+                    }
+                    _ => {},
+                }
                 helps
             }
             InvalidProgram(
@@ -339,7 +347,7 @@ pub fn report_error<'tcx, 'mir>(
     // We want to dump the allocation if this is `InvalidUninitBytes`. Since `format_error` consumes `e`, we compute the outut early.
     let mut extra = String::new();
     match e.kind() {
-        UndefinedBehavior(UndefinedBehaviorInfo::InvalidUninitBytes(Some((alloc_id, access)))) => {
+        UndefinedBehavior(InvalidUninitBytes(Some((alloc_id, access)))) => {
             writeln!(
                 extra,
                 "Uninitialized memory occurred at {alloc_id:?}{range:?}, in this allocation:",

src/tools/miri/tests/fail/function_pointers/abi_mismatch_array_vs_struct.stderr

@@ -6,6 +6,8 @@ LL |     g(Default::default())
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = help: this means these two types are not *guaranteed* to be ABI-compatible across all targets
+   = help: if you think this code should be accepted anyway, please report an issue
    = note: BACKTRACE:
    = note: inside `main` at $DIR/abi_mismatch_array_vs_struct.rs:LL:CC
 

src/tools/miri/tests/fail/function_pointers/abi_mismatch_int_vs_float.stderr

@@ -6,6 +6,8 @@ LL |     g(42)
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = help: this means these two types are not *guaranteed* to be ABI-compatible across all targets
+   = help: if you think this code should be accepted anyway, please report an issue
    = note: BACKTRACE:
    = note: inside `main` at $DIR/abi_mismatch_int_vs_float.rs:LL:CC
 

src/tools/miri/tests/fail/function_pointers/abi_mismatch_raw_pointer.stderr

@@ -6,6 +6,8 @@ LL |     g(&42 as *const i32)
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = help: this means these two types are not *guaranteed* to be ABI-compatible across all targets
+   = help: if you think this code should be accepted anyway, please report an issue
    = note: BACKTRACE:
    = note: inside `main` at $DIR/abi_mismatch_raw_pointer.rs:LL:CC
 

src/tools/miri/tests/fail/function_pointers/abi_mismatch_return_type.stderr

@@ -6,6 +6,8 @@ LL |     g()
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = help: this means these two types are not *guaranteed* to be ABI-compatible across all targets
+   = help: if you think this code should be accepted anyway, please report an issue
    = note: BACKTRACE:
    = note: inside `main` at $DIR/abi_mismatch_return_type.rs:LL:CC
 

src/tools/miri/tests/fail/function_pointers/abi_mismatch_simple.stderr

@@ -6,6 +6,8 @@ LL |     g(42)
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = help: this means these two types are not *guaranteed* to be ABI-compatible across all targets
+   = help: if you think this code should be accepted anyway, please report an issue
    = note: BACKTRACE:
    = note: inside `main` at $DIR/abi_mismatch_simple.rs:LL:CC
 

src/tools/miri/tests/fail/function_pointers/abi_mismatch_vector.stderr

@@ -6,6 +6,8 @@ LL |     g(Default::default())
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = help: this means these two types are not *guaranteed* to be ABI-compatible across all targets
+   = help: if you think this code should be accepted anyway, please report an issue
    = note: BACKTRACE:
    = note: inside `main` at $DIR/abi_mismatch_vector.rs:LL:CC