From 392ea7ad53845630a185c20dfa4a88c741cdf866 Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Sun, 30 Sep 2018 12:37:00 +0200 Subject: [PATCH] do not normalize non-scalar constants to a ConstValue::ScalarPair --- src/librustc/mir/interpret/value.rs | 15 +++++++++------ src/librustc/mir/mod.rs | 4 ++-- src/librustc_codegen_llvm/mir/operand.rs | 18 +++++++----------- src/librustc_mir/const_eval.rs | 16 +++++++++++++--- src/librustc_mir/hair/pattern/mod.rs | 7 ------- src/librustc_mir/interpret/operand.rs | 2 +- src/librustc_mir/monomorphize/collector.rs | 6 +++--- src/test/ui/consts/const-eval/union-ice.rs | 2 +- src/test/ui/consts/const-eval/union-ice.stderr | 8 +++++--- src/test/ui/issues/issue-54387.rs | 12 ++++++++++++ 10 files changed, 53 insertions(+), 37 deletions(-) create mode 100644 src/test/ui/issues/issue-54387.rs diff --git a/src/librustc/mir/interpret/value.rs b/src/librustc/mir/interpret/value.rs index be7d9b06fb4..bd1061d9bcf 100644 --- a/src/librustc/mir/interpret/value.rs +++ b/src/librustc/mir/interpret/value.rs @@ -24,15 +24,18 @@ pub enum ConstValue<'tcx> { /// to allow HIR creation to happen for everything before needing to be able to run constant /// evaluation Unevaluated(DefId, &'tcx Substs<'tcx>), + /// Used only for types with layout::abi::Scalar ABI and ZSTs /// /// Not using the enum `Value` to encode that this must not be `Undef` Scalar(Scalar), - /// Used only for types with layout::abi::ScalarPair + + /// Used only for *fat pointers* with layout::abi::ScalarPair /// - /// The second field may be undef in case of `Option::None` - ScalarPair(Scalar, ScalarMaybeUndef), - /// Used only for the remaining cases. An allocation + offset into the allocation. + /// Needed for pattern matching code related to slices and strings. + ScalarPair(Scalar, Scalar), + + /// An allocation + offset into the allocation. /// Invariant: The AllocId matches the allocation. ByRef(AllocId, &'tcx Allocation, Size), } @@ -67,12 +70,12 @@ impl<'tcx> ConstValue<'tcx> { ConstValue::ScalarPair(val, Scalar::Bits { bits: len as u128, size: cx.data_layout().pointer_size.bytes() as u8, - }.into()) + }) } #[inline] pub fn new_dyn_trait(val: Scalar, vtable: Pointer) -> Self { - ConstValue::ScalarPair(val, Scalar::Ptr(vtable).into()) + ConstValue::ScalarPair(val, Scalar::Ptr(vtable)) } } diff --git a/src/librustc/mir/mod.rs b/src/librustc/mir/mod.rs index 8fea749e5ab..6ef20f32d15 100644 --- a/src/librustc/mir/mod.rs +++ b/src/librustc/mir/mod.rs @@ -17,7 +17,7 @@ use hir::def::CtorKind; use hir::def_id::DefId; use hir::{self, HirId, InlineAsm}; use middle::region; -use mir::interpret::{ConstValue, EvalErrorKind, Scalar, ScalarMaybeUndef}; +use mir::interpret::{ConstValue, EvalErrorKind, Scalar}; use mir::visit::MirVisitable; use rustc_apfloat::ieee::{Double, Single}; use rustc_apfloat::Float; @@ -2397,7 +2397,7 @@ pub fn fmt_const_val(f: &mut impl Write, const_val: &ty::Const) -> fmt::Result { // print string literals if let ConstValue::ScalarPair(ptr, len) = value { if let Scalar::Ptr(ptr) = ptr { - if let ScalarMaybeUndef::Scalar(Scalar::Bits { bits: len, .. }) = len { + if let Scalar::Bits { bits: len, .. } = len { if let Ref(_, &ty::TyS { sty: Str, .. }, _) = ty.sty { return ty::tls::with(|tcx| { let alloc = tcx.alloc_map.lock().get(ptr.alloc_id); diff --git a/src/librustc_codegen_llvm/mir/operand.rs b/src/librustc_codegen_llvm/mir/operand.rs index bfa0e0a451e..ab43531240f 100644 --- a/src/librustc_codegen_llvm/mir/operand.rs +++ b/src/librustc_codegen_llvm/mir/operand.rs @@ -8,9 +8,8 @@ // option. This file may not be copied, modified, or distributed // except according to those terms. -use rustc::mir::interpret::ConstEvalErr; +use rustc::mir::interpret::{ConstValue, ConstEvalErr}; use rustc::mir; -use rustc::mir::interpret::{ConstValue, ScalarMaybeUndef}; use rustc::ty; use rustc::ty::layout::{self, Align, LayoutOf, TyLayout}; use rustc_data_structures::sync::Lrc; @@ -114,15 +113,12 @@ impl OperandRef<'ll, 'tcx> { layout.scalar_pair_element_llvm_type(bx.cx, 0, true), ); let b_layout = layout.scalar_pair_element_llvm_type(bx.cx, 1, true); - let b_llval = match b { - ScalarMaybeUndef::Scalar(b) => scalar_to_llvm( - bx.cx, - b, - b_scalar, - b_layout, - ), - ScalarMaybeUndef::Undef => C_undef(b_layout), - }; + let b_llval = scalar_to_llvm( + bx.cx, + b, + b_scalar, + b_layout, + ); OperandValue::Pair(a_llval, b_llval) }, ConstValue::ByRef(_, alloc, offset) => { diff --git a/src/librustc_mir/const_eval.rs b/src/librustc_mir/const_eval.rs index 99a49122ef7..07e2cfe1e80 100644 --- a/src/librustc_mir/const_eval.rs +++ b/src/librustc_mir/const_eval.rs @@ -17,7 +17,7 @@ use rustc::hir::{self, def_id::DefId}; use rustc::mir::interpret::ConstEvalErr; use rustc::mir; use rustc::ty::{self, TyCtxt, Instance, query::TyCtxtAt}; -use rustc::ty::layout::{LayoutOf, TyLayout}; +use rustc::ty::layout::{self, LayoutOf, TyLayout}; use rustc::ty::subst::Subst; use rustc_data_structures::indexed_vec::IndexVec; @@ -97,8 +97,18 @@ pub(crate) fn eval_promoted<'a, 'mir, 'tcx>( pub fn op_to_const<'tcx>( ecx: &CompileTimeEvalContext<'_, '_, 'tcx>, op: OpTy<'tcx>, - normalize: bool, + may_normalize: bool, ) -> EvalResult<'tcx, &'tcx ty::Const<'tcx>> { + // We do not normalize just any data. Only scalar layout and fat pointers. + let normalize = may_normalize + && match op.layout.abi { + layout::Abi::Scalar(..) => true, + layout::Abi::ScalarPair(..) => { + // Must be a fat pointer + op.layout.ty.builtin_deref(true).is_some() + }, + _ => false, + }; let normalized_op = if normalize { ecx.try_read_value(op)? } else { @@ -125,7 +135,7 @@ pub fn op_to_const<'tcx>( Ok(Value::Scalar(x)) => ConstValue::Scalar(x.not_undef()?), Ok(Value::ScalarPair(a, b)) => - ConstValue::ScalarPair(a.not_undef()?, b), + ConstValue::ScalarPair(a.not_undef()?, b.not_undef()?), }; Ok(ty::Const::from_const_value(ecx.tcx.tcx, val, op.layout.ty)) } diff --git a/src/librustc_mir/hair/pattern/mod.rs b/src/librustc_mir/hair/pattern/mod.rs index c72f8783685..b22cc4a1a42 100644 --- a/src/librustc_mir/hair/pattern/mod.rs +++ b/src/librustc_mir/hair/pattern/mod.rs @@ -1124,13 +1124,6 @@ pub fn compare_const_vals<'a, 'tcx>( len_b, ), ) if ptr_a.offset.bytes() == 0 && ptr_b.offset.bytes() == 0 => { - let len_a = len_a.not_undef().ok(); - let len_b = len_b.not_undef().ok(); - if len_a.is_none() || len_b.is_none() { - tcx.sess.struct_err("str slice len is undef").delay_as_bug(); - } - let len_a = len_a?; - let len_b = len_b?; if let Ok(len_a) = len_a.to_bits(tcx.data_layout.pointer_size) { if let Ok(len_b) = len_b.to_bits(tcx.data_layout.pointer_size) { if len_a == len_b { diff --git a/src/librustc_mir/interpret/operand.rs b/src/librustc_mir/interpret/operand.rs index fef2f916b41..8efd2c6af67 100644 --- a/src/librustc_mir/interpret/operand.rs +++ b/src/librustc_mir/interpret/operand.rs @@ -490,7 +490,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> Ok(Operand::Indirect(MemPlace::from_ptr(Pointer::new(id, offset), alloc.align))) }, ConstValue::ScalarPair(a, b) => - Ok(Operand::Immediate(Value::ScalarPair(a.into(), b))), + Ok(Operand::Immediate(Value::ScalarPair(a.into(), b.into()))), ConstValue::Scalar(x) => Ok(Operand::Immediate(Value::Scalar(x.into()))), } diff --git a/src/librustc_mir/monomorphize/collector.rs b/src/librustc_mir/monomorphize/collector.rs index ea01d17ac13..b2fa8349384 100644 --- a/src/librustc_mir/monomorphize/collector.rs +++ b/src/librustc_mir/monomorphize/collector.rs @@ -193,7 +193,7 @@ use rustc::hir::itemlikevisit::ItemLikeVisitor; use rustc::hir::Node; use rustc::hir::def_id::DefId; -use rustc::mir::interpret::{AllocId, ConstValue, ScalarMaybeUndef}; +use rustc::mir::interpret::{AllocId, ConstValue}; use rustc::middle::lang_items::{ExchangeMallocFnLangItem, StartFnLangItem}; use rustc::ty::subst::Substs; use rustc::ty::{self, TypeFoldable, Ty, TyCtxt, GenericParamDefKind}; @@ -1263,11 +1263,11 @@ fn collect_const<'a, 'tcx>( }; match val { ConstValue::Unevaluated(..) => bug!("const eval yielded unevaluated const"), - ConstValue::ScalarPair(Scalar::Ptr(a), ScalarMaybeUndef::Scalar(Scalar::Ptr(b))) => { + ConstValue::ScalarPair(Scalar::Ptr(a), Scalar::Ptr(b)) => { collect_miri(tcx, a.alloc_id, output); collect_miri(tcx, b.alloc_id, output); } - ConstValue::ScalarPair(_, ScalarMaybeUndef::Scalar(Scalar::Ptr(ptr))) | + ConstValue::ScalarPair(_, Scalar::Ptr(ptr)) | ConstValue::ScalarPair(Scalar::Ptr(ptr), _) | ConstValue::Scalar(Scalar::Ptr(ptr)) => collect_miri(tcx, ptr.alloc_id, output), diff --git a/src/test/ui/consts/const-eval/union-ice.rs b/src/test/ui/consts/const-eval/union-ice.rs index 0cdb78c9780..5d50004e554 100644 --- a/src/test/ui/consts/const-eval/union-ice.rs +++ b/src/test/ui/consts/const-eval/union-ice.rs @@ -22,7 +22,7 @@ const UNION: DummyUnion = DummyUnion { field1: 1065353216 }; const FIELD3: Field3 = unsafe { UNION.field3 }; //~ ERROR this constant cannot be used -const FIELD_PATH: Struct = Struct { //~ ERROR this constant cannot be used +const FIELD_PATH: Struct = Struct { //~ ERROR this constant likely exhibits undefined behavior a: 42, b: unsafe { UNION.field3 }, }; diff --git a/src/test/ui/consts/const-eval/union-ice.stderr b/src/test/ui/consts/const-eval/union-ice.stderr index e8a7b2f5005..ec51802681e 100644 --- a/src/test/ui/consts/const-eval/union-ice.stderr +++ b/src/test/ui/consts/const-eval/union-ice.stderr @@ -6,14 +6,16 @@ LL | const FIELD3: Field3 = unsafe { UNION.field3 }; //~ ERROR this constant can | = note: #[deny(const_err)] on by default -error: this constant cannot be used +error[E0080]: this constant likely exhibits undefined behavior --> $DIR/union-ice.rs:25:1 | -LL | / const FIELD_PATH: Struct = Struct { //~ ERROR this constant cannot be used +LL | / const FIELD_PATH: Struct = Struct { //~ ERROR this constant likely exhibits undefined behavior LL | | a: 42, LL | | b: unsafe { UNION.field3 }, LL | | }; - | |__^ attempted to read undefined bytes + | |__^ type validation failed: encountered undefined bytes at .b + | + = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior error[E0080]: this constant likely exhibits undefined behavior --> $DIR/union-ice.rs:35:1 diff --git a/src/test/ui/issues/issue-54387.rs b/src/test/ui/issues/issue-54387.rs new file mode 100644 index 00000000000..ac1033add0e --- /dev/null +++ b/src/test/ui/issues/issue-54387.rs @@ -0,0 +1,12 @@ +// compile-pass + +pub struct GstRc { + _obj: *const (), + _borrowed: bool, +} + +const FOO: Option = None; + +fn main() { + let _meh = FOO; +}