Panic for size_of_val and align_of_val of extern type

cc rust-lang/rust#118534

Author: bjorn3

src/base.rs

@@ -353,7 +353,7 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
                             fx,
                             rustc_hir::LangItem::PanicBoundsCheck,
                             &[index, len, location],
-                            source_info.span,
+                            Some(source_info.span),
                         );
                     }
                     AssertKind::MisalignedPointerDereference { ref required, ref found } => {
@@ -365,7 +365,7 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
                             fx,
                             rustc_hir::LangItem::PanicMisalignedPointerDereference,
                             &[required, found, location],
-                            source_info.span,
+                            Some(source_info.span),
                         );
                     }
                     _ => {
@@ -945,19 +945,19 @@ pub(crate) fn codegen_panic<'tcx>(
     let msg_len = fx.bcx.ins().iconst(fx.pointer_type, i64::try_from(msg_str.len()).unwrap());
     let args = [msg_ptr, msg_len, location];
 
-    codegen_panic_inner(fx, rustc_hir::LangItem::Panic, &args, source_info.span);
+    codegen_panic_inner(fx, rustc_hir::LangItem::Panic, &args, Some(source_info.span));
 }
 
 pub(crate) fn codegen_panic_nounwind<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     msg_str: &str,
-    source_info: mir::SourceInfo,
+    span: Option<Span>,
 ) {
     let msg_ptr = fx.anonymous_str(msg_str);
     let msg_len = fx.bcx.ins().iconst(fx.pointer_type, i64::try_from(msg_str.len()).unwrap());
     let args = [msg_ptr, msg_len];
 
-    codegen_panic_inner(fx, rustc_hir::LangItem::PanicNounwind, &args, source_info.span);
+    codegen_panic_inner(fx, rustc_hir::LangItem::PanicNounwind, &args, span);
 }
 
 pub(crate) fn codegen_unwind_terminate<'tcx>(
@@ -967,16 +967,16 @@ pub(crate) fn codegen_unwind_terminate<'tcx>(
 ) {
     let args = [];
 
-    codegen_panic_inner(fx, reason.lang_item(), &args, source_info.span);
+    codegen_panic_inner(fx, reason.lang_item(), &args, Some(source_info.span));
 }
 
 fn codegen_panic_inner<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     lang_item: rustc_hir::LangItem,
     args: &[Value],
-    span: Span,
+    span: Option<Span>,
 ) {
-    let def_id = fx.tcx.require_lang_item(lang_item, Some(span));
+    let def_id = fx.tcx.require_lang_item(lang_item, span);
 
     let instance = Instance::mono(fx.tcx, def_id).polymorphize(fx.tcx);
     let symbol_name = fx.tcx.symbol_name(instance).name;

src/intrinsics/mod.rs

@@ -487,13 +487,12 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let layout = fx.layout_of(generic_args.type_at(0));
             // Note: Can't use is_unsized here as truly unsized types need to take the fixed size
             // branch
-            let size = if let Abi::ScalarPair(_, _) = ptr.layout().abi {
-                let (_ptr, info) = ptr.load_scalar_pair(fx);
-                let (size, _align) = crate::unsize::size_and_align_of_dst(fx, layout, info);
-                size
+            let meta = if let Abi::ScalarPair(_, _) = ptr.layout().abi {
+                Some(ptr.load_scalar_pair(fx).1)
             } else {
-                fx.bcx.ins().iconst(fx.pointer_type, layout.size.bytes() as i64)
+                None
             };
+            let (size, _align) = crate::unsize::size_and_align_of(fx, layout, meta);
             ret.write_cvalue(fx, CValue::by_val(size, usize_layout));
         }
         sym::min_align_of_val => {
@@ -502,13 +501,12 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let layout = fx.layout_of(generic_args.type_at(0));
             // Note: Can't use is_unsized here as truly unsized types need to take the fixed size
             // branch
-            let align = if let Abi::ScalarPair(_, _) = ptr.layout().abi {
-                let (_ptr, info) = ptr.load_scalar_pair(fx);
-                let (_size, align) = crate::unsize::size_and_align_of_dst(fx, layout, info);
-                align
+            let meta = if let Abi::ScalarPair(_, _) = ptr.layout().abi {
+                Some(ptr.load_scalar_pair(fx).1)
             } else {
-                fx.bcx.ins().iconst(fx.pointer_type, layout.align.abi.bytes() as i64)
+                None
             };
+            let (_size, align) = crate::unsize::size_and_align_of(fx, layout, meta);
             ret.write_cvalue(fx, CValue::by_val(align, usize_layout));
         }
 
@@ -688,7 +686,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
                             }
                         })
                     });
-                    crate::base::codegen_panic_nounwind(fx, &msg_str, source_info);
+                    crate::base::codegen_panic_nounwind(fx, &msg_str, Some(source_info.span));
                     return;
                 }
             }

src/unsize.rs

@@ -2,6 +2,9 @@
 //!
 //! [`PointerCoercion::Unsize`]: `rustc_middle::ty::adjustment::PointerCoercion::Unsize`
 
+use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
+
+use crate::base::codegen_panic_nounwind;
 use crate::prelude::*;
 
 // Adapted from https://github.com/rust-lang/rust/blob/2a663555ddf36f6b041445894a8c175cd1bc718c/src/librustc_codegen_ssa/base.rs#L159-L307
@@ -187,27 +190,62 @@ pub(crate) fn coerce_dyn_star<'tcx>(
 
 // Adapted from https://github.com/rust-lang/rust/blob/2a663555ddf36f6b041445894a8c175cd1bc718c/src/librustc_codegen_ssa/glue.rs
 
-pub(crate) fn size_and_align_of_dst<'tcx>(
+pub(crate) fn size_and_align_of<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     layout: TyAndLayout<'tcx>,
-    info: Value,
+    info: Option<Value>,
 ) -> (Value, Value) {
-    assert!(layout.is_unsized() || layout.abi == Abi::Uninhabited);
-    match layout.ty.kind() {
+    if layout.is_sized() {
+        return (
+            fx.bcx.ins().iconst(fx.pointer_type, layout.size.bytes() as i64),
+            fx.bcx.ins().iconst(fx.pointer_type, layout.align.abi.bytes() as i64),
+        );
+    }
+
+    let ty = layout.ty;
+    match ty.kind() {
         ty::Dynamic(..) => {
             // load size/align from vtable
-            (crate::vtable::size_of_obj(fx, info), crate::vtable::min_align_of_obj(fx, info))
+            (
+                crate::vtable::size_of_obj(fx, info.unwrap()),
+                crate::vtable::min_align_of_obj(fx, info.unwrap()),
+            )
         }
         ty::Slice(_) | ty::Str => {
             let unit = layout.field(fx, 0);
             // The info in this case is the length of the str, so the size is that
             // times the unit size.
             (
-                fx.bcx.ins().imul_imm(info, unit.size.bytes() as i64),
+                fx.bcx.ins().imul_imm(info.unwrap(), unit.size.bytes() as i64),
                 fx.bcx.ins().iconst(fx.pointer_type, unit.align.abi.bytes() as i64),
             )
         }
-        _ => {
+        ty::Foreign(_) => {
+            let trap_block = fx.bcx.create_block();
+            let true_ = fx.bcx.ins().iconst(types::I8, 1);
+            let next_block = fx.bcx.create_block();
+            fx.bcx.ins().brif(true_, trap_block, &[], next_block, &[]);
+            fx.bcx.seal_block(trap_block);
+            fx.bcx.seal_block(next_block);
+            fx.bcx.switch_to_block(trap_block);
+
+            // `extern` type. We cannot compute the size, so panic.
+            let msg_str = with_no_visible_paths!({
+                with_no_trimmed_paths!({
+                    format!("attempted to compute the size or alignment of extern type `{ty}`")
+                })
+            });
+
+            codegen_panic_nounwind(fx, &msg_str, None);
+
+            fx.bcx.switch_to_block(next_block);
+
+            // This function does not return so we can now return whatever we want.
+            let size = fx.bcx.ins().iconst(fx.pointer_type, 42);
+            let align = fx.bcx.ins().iconst(fx.pointer_type, 42);
+            (size, align)
+        }
+        ty::Adt(..) | ty::Tuple(..) => {
             // First get the size of all statically known fields.
             // Don't use size_of because it also rounds up to alignment, which we
             // want to avoid, as the unsized field's alignment could be smaller.
@@ -221,7 +259,7 @@ pub(crate) fn size_and_align_of_dst<'tcx>(
             // Recurse to get the size of the dynamically sized field (must be
             // the last field).
             let field_layout = layout.field(fx, i);
-            let (unsized_size, mut unsized_align) = size_and_align_of_dst(fx, field_layout, info);
+            let (unsized_size, mut unsized_align) = size_and_align_of(fx, field_layout, info);
 
             // FIXME (#26403, #27023): We should be adding padding
             // to `sized_size` (to accommodate the `unsized_align`
@@ -262,5 +300,6 @@ pub(crate) fn size_and_align_of_dst<'tcx>(
 
             (size, align)
         }
+        _ => bug!("size_and_align_of_dst: {ty} not supported"),
     }
 }

src/value_and_place.rs

@@ -20,34 +20,29 @@ fn codegen_field<'tcx>(
         (base.offset_i64(fx, i64::try_from(field_offset.bytes()).unwrap()), field_layout)
     };
 
-    if let Some(extra) = extra {
-        if field_layout.is_sized() {
-            return simple(fx);
+    if field_layout.is_sized() {
+        return simple(fx);
+    }
+    match field_layout.ty.kind() {
+        ty::Slice(..) | ty::Str => simple(fx),
+        ty::Adt(def, _) if def.repr().packed() => {
+            assert_eq!(layout.align.abi.bytes(), 1);
+            simple(fx)
         }
-        match field_layout.ty.kind() {
-            ty::Slice(..) | ty::Str | ty::Foreign(..) => simple(fx),
-            ty::Adt(def, _) if def.repr().packed() => {
-                assert_eq!(layout.align.abi.bytes(), 1);
-                simple(fx)
-            }
-            _ => {
-                // We have to align the offset for DST's
-                let unaligned_offset = field_offset.bytes();
-                let (_, unsized_align) =
-                    crate::unsize::size_and_align_of_dst(fx, field_layout, extra);
+        _ => {
+            // We have to align the offset for DST's
+            let unaligned_offset = field_offset.bytes();
+            let (_, unsized_align) = crate::unsize::size_and_align_of(fx, field_layout, extra);
 
-                let one = fx.bcx.ins().iconst(fx.pointer_type, 1);
-                let align_sub_1 = fx.bcx.ins().isub(unsized_align, one);
-                let and_lhs = fx.bcx.ins().iadd_imm(align_sub_1, unaligned_offset as i64);
-                let zero = fx.bcx.ins().iconst(fx.pointer_type, 0);
-                let and_rhs = fx.bcx.ins().isub(zero, unsized_align);
-                let offset = fx.bcx.ins().band(and_lhs, and_rhs);
+            let one = fx.bcx.ins().iconst(fx.pointer_type, 1);
+            let align_sub_1 = fx.bcx.ins().isub(unsized_align, one);
+            let and_lhs = fx.bcx.ins().iadd_imm(align_sub_1, unaligned_offset as i64);
+            let zero = fx.bcx.ins().iconst(fx.pointer_type, 0);
+            let and_rhs = fx.bcx.ins().isub(zero, unsized_align);
+            let offset = fx.bcx.ins().band(and_lhs, and_rhs);
 
-                (base.offset_value(fx, offset), field_layout)
-            }
+            (base.offset_value(fx, offset), field_layout)
         }
-    } else {
-        simple(fx)
     }
 }
 
@@ -731,13 +726,8 @@ impl<'tcx> CPlace<'tcx> {
         };
 
         let (field_ptr, field_layout) = codegen_field(fx, base, extra, layout, field);
-        if field_layout.is_unsized() {
-            if let ty::Foreign(_) = field_layout.ty.kind() {
-                assert!(extra.is_none());
-                CPlace::for_ptr(field_ptr, field_layout)
-            } else {
-                CPlace::for_ptr_with_extra(field_ptr, extra.unwrap(), field_layout)
-            }
+        if has_ptr_meta(fx.tcx, field_layout.ty) {
+            CPlace::for_ptr_with_extra(field_ptr, extra.unwrap(), field_layout)
         } else {
             CPlace::for_ptr(field_ptr, field_layout)
         }