give Pointer::into_parts a more scary name and offer a safer alternative

Author: RalfJung

compiler/rustc_codegen_cranelift/src/constant.rs

@@ -133,7 +133,7 @@ pub(crate) fn codegen_const_value<'tcx>(
                 }
             }
             Scalar::Ptr(ptr, _size) => {
-                let (prov, offset) = ptr.into_parts(); // we know the `offset` is relative
+                let (prov, offset) = ptr.prov_and_relative_offset();
                 let alloc_id = prov.alloc_id();
                 let base_addr = match fx.tcx.global_alloc(alloc_id) {
                     GlobalAlloc::Memory(alloc) => {

compiler/rustc_codegen_gcc/src/common.rs

@@ -261,7 +261,7 @@ impl<'gcc, 'tcx> ConstCodegenMethods for CodegenCx<'gcc, 'tcx> {
                 }
             }
             Scalar::Ptr(ptr, _size) => {
-                let (prov, offset) = ptr.into_parts(); // we know the `offset` is relative
+                let (prov, offset) = ptr.prov_and_relative_offset();
                 let alloc_id = prov.alloc_id();
                 let base_addr = match self.tcx.global_alloc(alloc_id) {
                     GlobalAlloc::Memory(alloc) => {

compiler/rustc_codegen_llvm/src/common.rs

@@ -268,7 +268,7 @@ impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> {
                 }
             }
             Scalar::Ptr(ptr, _size) => {
-                let (prov, offset) = ptr.into_parts();
+                let (prov, offset) = ptr.prov_and_relative_offset();
                 let global_alloc = self.tcx.global_alloc(prov.alloc_id());
                 let base_addr = match global_alloc {
                     GlobalAlloc::Memory(alloc) => {

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -209,9 +209,9 @@ pub(super) fn op_to_const<'tcx>(
 
     match immediate {
         Left(ref mplace) => {
-            // We know `offset` is relative to the allocation, so we can use `into_parts`.
-            let (prov, offset) = mplace.ptr().into_parts();
-            let alloc_id = prov.expect("cannot have `fake` place for non-ZST type").alloc_id();
+            let (prov, offset) =
+                mplace.ptr().into_pointer_or_addr().unwrap().prov_and_relative_offset();
+            let alloc_id = prov.alloc_id();
             ConstValue::Indirect { alloc_id, offset }
         }
         // see comment on `let force_as_immediate` above
@@ -232,9 +232,10 @@ pub(super) fn op_to_const<'tcx>(
                     imm.layout.ty,
                 );
                 let msg = "`op_to_const` on an immediate scalar pair must only be used on slice references to the beginning of an actual allocation";
-                // We know `offset` is relative to the allocation, so we can use `into_parts`.
-                let (prov, offset) = a.to_pointer(ecx).expect(msg).into_parts();
-                let alloc_id = prov.expect(msg).alloc_id();
+                let ptr = a.to_pointer(ecx).expect(msg);
+                let (prov, offset) =
+                    ptr.into_pointer_or_addr().expect(msg).prov_and_relative_offset();
+                let alloc_id = prov.alloc_id();
                 let data = ecx.tcx.global_alloc(alloc_id).unwrap_memory();
                 assert!(offset == abi::Size::ZERO, "{}", msg);
                 let meta = b.to_target_usize(ecx).expect(msg);

compiler/rustc_const_eval/src/interpret/machine.rs

@@ -756,8 +756,7 @@ pub macro compile_time_machine(<$tcx: lifetime>) {
         ptr: Pointer<CtfeProvenance>,
         _size: i64,
     ) -> Option<(AllocId, Size, Self::ProvenanceExtra)> {
-        // We know `offset` is relative to the allocation, so we can use `into_parts`.
-        let (prov, offset) = ptr.into_parts();
+        let (prov, offset) = ptr.prov_and_relative_offset();
         Some((prov.alloc_id(), offset, prov.immutable()))
     }
 

compiler/rustc_const_eval/src/interpret/memory.rs

@@ -1596,7 +1596,8 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 Some((alloc_id, offset, extra)) => Ok((alloc_id, offset, extra)),
                 None => {
                     assert!(M::Provenance::OFFSET_IS_ADDR);
-                    let (_, addr) = ptr.into_parts();
+                    // Offset is absolute, as we just asserted.
+                    let (_, addr) = ptr.into_raw_parts();
                     Err(addr.bytes())
                 }
             },

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -868,7 +868,9 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
     fn add_data_range(&mut self, ptr: Pointer<Option<M::Provenance>>, size: Size) {
         if let Some(data_bytes) = self.data_bytes.as_mut() {
             // We only have to store the offset, the rest is the same for all pointers here.
-            let (_prov, offset) = ptr.into_parts();
+            // The logic is agnostic to wether the offset is relative or absolute as long as
+            // it is consistent.
+            let (_prov, offset) = ptr.into_raw_parts();
             // Add this.
             data_bytes.add_range(offset, size);
         };
@@ -894,7 +896,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
             .as_mplace_or_imm()
             .expect_left("place must be in memory")
             .ptr();
-        let (_prov, offset) = ptr.into_parts();
+        let (_prov, offset) = ptr.into_raw_parts();
         offset
     }
 
@@ -903,7 +905,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
         // Our value must be in memory, otherwise we would not have set up `data_bytes`.
         let mplace = self.ecx.force_allocation(place)?;
         // Determine starting offset and size.
-        let (_prov, start_offset) = mplace.ptr().into_parts();
+        let (_prov, start_offset) = mplace.ptr().into_raw_parts();
         let (size, _align) = self
             .ecx
             .size_and_align_of_val(&mplace)?

compiler/rustc_middle/src/mir/consts.rs

@@ -168,8 +168,9 @@ impl<'tcx> ConstValue<'tcx> {
                     return Some(&[]);
                 }
                 // Non-empty slice, must have memory. We know this is a relative pointer.
-                let (inner_prov, offset) = ptr.into_parts();
-                let data = tcx.global_alloc(inner_prov?.alloc_id()).unwrap_memory();
+                let (inner_prov, offset) =
+                    ptr.into_pointer_or_addr().ok()?.prov_and_relative_offset();
+                let data = tcx.global_alloc(inner_prov.alloc_id()).unwrap_memory();
                 (data, offset.bytes(), offset.bytes() + len)
             }
         };

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

@@ -526,7 +526,7 @@ impl Allocation {
             let ptr_bytes = &mut bytes[idx..idx + ptr_size];
             let bits = read_target_uint(endian, ptr_bytes).unwrap();
             let (ptr_prov, ptr_offset) =
-                adjust_ptr(Pointer::new(alloc_id, Size::from_bytes(bits)))?.into_parts();
+                adjust_ptr(Pointer::new(alloc_id, Size::from_bytes(bits)))?.into_raw_parts();
             write_target_uint(endian, ptr_bytes, ptr_offset.bytes().into()).unwrap();
             new_provenance.push((offset, ptr_prov));
         }
@@ -769,7 +769,7 @@ impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes>
         // as-is into memory. This also double-checks that `val.size()` matches `range.size`.
         let (bytes, provenance) = match val.to_bits_or_ptr_internal(range.size)? {
             Right(ptr) => {
-                let (provenance, offset) = ptr.into_parts();
+                let (provenance, offset) = ptr.into_raw_parts();
                 (u128::from(offset.bytes()), Some(provenance))
             }
             Left(data) => (data, None),

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

@@ -288,7 +288,7 @@ impl From<CtfeProvenance> for Pointer {
 impl<Prov> From<Pointer<Prov>> for Pointer<Option<Prov>> {
     #[inline(always)]
     fn from(ptr: Pointer<Prov>) -> Self {
-        let (prov, offset) = ptr.into_parts();
+        let (prov, offset) = ptr.into_raw_parts();
         Pointer::new(Some(prov), offset)
     }
 }
@@ -314,9 +314,7 @@ impl<Prov> Pointer<Option<Prov>> {
         assert!(Prov::OFFSET_IS_ADDR);
         self.offset
     }
-}
 
-impl<Prov> Pointer<Option<Prov>> {
     /// Creates a pointer to the given address, with invalid provenance (i.e., cannot be used for
     /// any memory access).
     #[inline(always)]
@@ -336,11 +334,11 @@ impl<Prov> Pointer<Prov> {
         Pointer { provenance, offset }
     }
 
-    /// Obtain the constituents of this pointer. Not that the meaning of the offset depends on the type `Prov`!
-    /// This function must only be used in the implementation of `Machine::ptr_get_alloc`,
-    /// and when a `Pointer` is taken apart to be stored efficiently in an `Allocation`.
+    /// Obtain the constituents of this pointer. Not that the meaning of the offset depends on the
+    /// type `Prov`! This is a low-level function that should only be used when absolutely
+    /// necessary. Prefer `prov_and_relative_offset` if possible.
     #[inline(always)]
-    pub fn into_parts(self) -> (Prov, Size) {
+    pub fn into_raw_parts(self) -> (Prov, Size) {
         (self.provenance, self.offset)
     }
 
@@ -361,3 +359,12 @@ impl<Prov> Pointer<Prov> {
         self.wrapping_offset(Size::from_bytes(i as u64), cx)
     }
 }
+
+impl Pointer<CtfeProvenance> {
+    /// Return the provenance and relative offset stored in this pointer. Safer alternative to
+    /// `into_raw_parts` since the type ensures that the offset is indeed relative.
+    #[inline(always)]
+    pub fn prov_and_relative_offset(self) -> (CtfeProvenance, Size) {
+        (self.provenance, self.offset)
+    }
+}

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

@@ -109,7 +109,7 @@ impl<Prov> Scalar<Prov> {
     /// Create a Scalar from a pointer with an `Option<_>` provenance (where `None` represents a
     /// plain integer / "invalid" pointer).
     pub fn from_maybe_pointer(ptr: Pointer<Option<Prov>>, cx: &impl HasDataLayout) -> Self {
-        match ptr.into_parts() {
+        match ptr.into_raw_parts() {
             (Some(prov), offset) => Scalar::from_pointer(Pointer::new(prov, offset), cx),
             (None, offset) => {
                 Scalar::Int(ScalarInt::try_from_uint(offset.bytes(), cx.pointer_size()).unwrap())
@@ -299,7 +299,7 @@ impl<'tcx, Prov: Provenance> Scalar<Prov> {
                     Ok(ScalarInt::try_from_uint(ptr.offset.bytes(), Size::from_bytes(sz)).unwrap())
                 } else {
                     // We know `offset` is relative, since `OFFSET_IS_ADDR == false`.
-                    let (prov, offset) = ptr.into_parts();
+                    let (prov, offset) = ptr.into_raw_parts();
                     // Because `OFFSET_IS_ADDR == false`, this unwrap can never fail.
                     Err(Scalar::Ptr(Pointer::new(prov.get_alloc_id().unwrap(), offset), sz))
                 }

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -1755,7 +1755,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
     ) -> Result<(), PrintError> {
         define_scoped_cx!(self);
 
-        let (prov, offset) = ptr.into_parts();
+        let (prov, offset) = ptr.prov_and_relative_offset();
         match ty.kind() {
             // Byte strings (&[u8; N])
             ty::Ref(_, inner, _) => {

compiler/rustc_mir_transform/src/gvn.rs

@@ -1636,7 +1636,7 @@ fn op_to_prop_const<'tcx>(
         }
 
         let pointer = mplace.ptr().into_pointer_or_addr().ok()?;
-        let (prov, offset) = pointer.into_parts();
+        let (prov, offset) = pointer.prov_and_relative_offset();
         let alloc_id = prov.alloc_id();
         intern_const_alloc_for_constprop(ecx, alloc_id).discard_err()?;
 

src/tools/miri/src/alloc_addresses/mod.rs

@@ -390,7 +390,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     ) -> InterpResult<'tcx, interpret::Pointer<Provenance>> {
         let this = self.eval_context_ref();
 
-        let (prov, offset) = ptr.into_parts(); // offset is relative (AllocId provenance)
+        let (prov, offset) = ptr.prov_and_relative_offset();
         let alloc_id = prov.alloc_id();
 
         // Get a pointer to the beginning of this allocation.
@@ -447,7 +447,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
     ) -> Option<(AllocId, Size)> {
         let this = self.eval_context_ref();
 
-        let (tag, addr) = ptr.into_parts(); // addr is absolute (Tag provenance)
+        let (tag, addr) = ptr.into_raw_parts(); // addr is absolute (Miri provenance)
 
         let alloc_id = if let Provenance::Concrete { alloc_id, .. } = tag {
             alloc_id

src/tools/miri/src/machine.rs

@@ -285,7 +285,7 @@ impl interpret::Provenance for Provenance {
     }
 
     fn fmt(ptr: &interpret::Pointer<Self>, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let (prov, addr) = ptr.into_parts(); // address is absolute
+        let (prov, addr) = ptr.into_raw_parts(); // offset is absolute address
         write!(f, "{:#x}", addr.bytes())?;
         if f.alternate() {
             write!(f, "{prov:#?}")?;

src/tools/miri/src/provenance_gc.rs

@@ -68,15 +68,13 @@ impl VisitProvenance for Provenance {
 
 impl VisitProvenance for StrictPointer {
     fn visit_provenance(&self, visit: &mut VisitWith<'_>) {
-        let (prov, _offset) = self.into_parts();
-        prov.visit_provenance(visit);
+        self.provenance.visit_provenance(visit);
     }
 }
 
 impl VisitProvenance for Pointer {
     fn visit_provenance(&self, visit: &mut VisitWith<'_>) {
-        let (prov, _offset) = self.into_parts();
-        prov.visit_provenance(visit);
+        self.provenance.visit_provenance(visit);
     }
 }
 

src/tools/miri/src/shims/foreign_items.rs

@@ -411,7 +411,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                         AlignFromBytesError::TooLarge(_) => Align::MAX,
                     }
                 });
-                let (_, addr) = ptr.into_parts(); // we know the offset is absolute
+                let addr = ptr.addr();
                 // Cannot panic since `align` is a power of 2 and hence non-zero.
                 if addr.bytes().strict_rem(align.bytes()) != 0 {
                     throw_unsup_format!(