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Simplify vtable interning

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oli-obk committed Jun 24, 2019
1 parent 166c49d commit 354163d478a4fc089af07203948036c4b1e237d3
@@ -3,7 +3,6 @@
//! After a const evaluation has computed a value, before we destroy the const evaluator's session
//! memory, we need to extract all memory allocations to the global memory pool so they stay around.

use rustc::ty::layout::LayoutOf;
use rustc::ty::{Ty, TyCtxt, ParamEnv, self};
use rustc::mir::interpret::{
InterpResult, ErrorHandled,
@@ -143,21 +142,18 @@ for
// Handle Reference types, as these are the only relocations supported by const eval.
// Raw pointers (and boxes) are handled by the `leftover_relocations` logic.
let ty = mplace.layout.ty;
if let ty::Ref(_, _, mutability) = ty.sty {
if let ty::Ref(_, referenced_ty, mutability) = ty.sty {
let value = self.ecx.read_immediate(mplace.into())?;
// Handle trait object vtables
if let Ok(meta) = value.to_meta() {
let layout = self.ecx.layout_of(ty.builtin_deref(true).unwrap().ty)?;
if layout.is_unsized() {
if let ty::Dynamic(..) = self.ecx.tcx.struct_tail(layout.ty).sty {
if let ty::Dynamic(..) = self.ecx.tcx.struct_tail(referenced_ty).sty {
if let Ok(vtable) = meta.unwrap().to_ptr() {
// explitly choose `Immutable` here, since vtables are immutable, even
// if the reference of the fat pointer is mutable
self.intern_shallow(vtable, Mutability::Immutable)?;
}
}
}
}
let mplace = self.ecx.ref_to_mplace(value)?;
// Check if we have encountered this pointer+layout combination before.
// Only recurse for allocation-backed pointers.
@@ -3,6 +3,7 @@
// rustc-env:RUST_BACKTRACE=0
// normalize-stderr-test "note: rustc 1.* running on .*" -> "note: rustc VERSION running on TARGET"
// normalize-stderr-test "note: compiler flags: .*" -> "note: compiler flags: FLAGS"
// normalize-stderr-test "src/librustc_mir/interpret/intern.rs:[0-9]*:[0-9]*" -> "src/librustc_mir/interpret/intern.rs:LL:CC"

#![allow(const_err)]

@@ -1,12 +1,12 @@
warning: skipping const checks
--> $DIR/mutable_references_ice.rs:26:9
--> $DIR/mutable_references_ice.rs:27:9
|
LL | *MUH.x.get() = 99;
| ^^^^^^^^^^^^^^^^^

thread 'rustc' panicked at 'assertion failed: `(left != right)`
left: `Const`,
right: `Const`: UnsafeCells are not allowed behind references in constants. This should have been prevented statically by const qualification. If this were allowed one would be able to change a constant at one use site and other use sites may arbitrarily decide to change, too.', src/librustc_mir/interpret/intern.rs:127:17
right: `Const`: UnsafeCells are not allowed behind references in constants. This should have been prevented statically by const qualification. If this were allowed one would be able to change a constant at one use site and other use sites may arbitrarily decide to change, too.', src/librustc_mir/interpret/intern.rs:LL:CC
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.

error: internal compiler error: unexpected panic

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