make return type of get_alloc_info a struct, and reduce some code duplication with validity checking

Author: RalfJung

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -472,8 +472,9 @@ fn report_validation_error<'tcx>(
     backtrace.print_backtrace();
 
     let bytes = ecx.print_alloc_bytes_for_diagnostics(alloc_id);
-    let (size, align, ..) = ecx.get_alloc_info(alloc_id);
-    let raw_bytes = errors::RawBytesNote { size: size.bytes(), align: align.bytes(), bytes };
+    let info = ecx.get_alloc_info(alloc_id);
+    let raw_bytes =
+        errors::RawBytesNote { size: info.size.bytes(), align: info.align.bytes(), bytes };
 
     crate::const_eval::report(
         *ecx.tcx,

compiler/rustc_const_eval/src/interpret/memory.rs

@@ -72,6 +72,21 @@ pub enum AllocKind {
     Dead,
 }
 
+/// Metadata about an `AllocId`.
+#[derive(Copy, Clone, PartialEq, Debug)]
+pub struct AllocInfo {
+    pub size: Size,
+    pub align: Align,
+    pub kind: AllocKind,
+    pub mutbl: Mutability,
+}
+
+impl AllocInfo {
+    fn new(size: Size, align: Align, kind: AllocKind, mutbl: Mutability) -> Self {
+        Self { size, align, kind, mutbl }
+    }
+}
+
 /// The value of a function pointer.
 #[derive(Debug, Copy, Clone)]
 pub enum FnVal<'tcx, Other> {
@@ -524,17 +539,22 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         match self.ptr_try_get_alloc_id(ptr, 0) {
             Err(addr) => is_offset_misaligned(addr, align),
             Ok((alloc_id, offset, _prov)) => {
-                let (_size, alloc_align, kind, _mutbl) = self.get_alloc_info(alloc_id);
-                if let Some(misalign) =
-                    M::alignment_check(self, alloc_id, alloc_align, kind, offset, align)
-                {
+                let alloc_info = self.get_alloc_info(alloc_id);
+                if let Some(misalign) = M::alignment_check(
+                    self,
+                    alloc_id,
+                    alloc_info.align,
+                    alloc_info.kind,
+                    offset,
+                    align,
+                ) {
                     Some(misalign)
                 } else if M::Provenance::OFFSET_IS_ADDR {
                     is_offset_misaligned(ptr.addr().bytes(), align)
                 } else {
                     // Check allocation alignment and offset alignment.
-                    if alloc_align.bytes() < align.bytes() {
-                        Some(Misalignment { has: alloc_align, required: align })
+                    if alloc_info.align.bytes() < align.bytes() {
+                        Some(Misalignment { has: alloc_info.align, required: align })
                     } else {
                         is_offset_misaligned(offset.bytes(), align)
                     }
@@ -818,19 +838,24 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
 
     /// Obtain the size and alignment of an allocation, even if that allocation has
     /// been deallocated.
-    pub fn get_alloc_info(&self, id: AllocId) -> (Size, Align, AllocKind, Mutability) {
+    pub fn get_alloc_info(&self, id: AllocId) -> AllocInfo {
         // # Regular allocations
         // Don't use `self.get_raw` here as that will
         // a) cause cycles in case `id` refers to a static
         // b) duplicate a global's allocation in miri
         if let Some((_, alloc)) = self.memory.alloc_map.get(id) {
-            return (alloc.size(), alloc.align, AllocKind::LiveData, alloc.mutability);
+            return AllocInfo::new(
+                alloc.size(),
+                alloc.align,
+                AllocKind::LiveData,
+                alloc.mutability,
+            );
         }
 
         // # Function pointers
         // (both global from `alloc_map` and local from `extra_fn_ptr_map`)
         if self.get_fn_alloc(id).is_some() {
-            return (Size::ZERO, Align::ONE, AllocKind::Function, Mutability::Not);
+            return AllocInfo::new(Size::ZERO, Align::ONE, AllocKind::Function, Mutability::Not);
         }
 
         // # Statics
@@ -852,7 +877,10 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                     // succeeds, as the query is fed at DefId creation time, so no
                     // evaluation actually occurs.
                     let alloc = self.tcx.eval_static_initializer(def_id).unwrap();
-                    (alloc.0.size(), alloc.0.align, alloc.0.mutability)
+                    // Nested statics in a `static` are never interior mutable, so just use the
+                    // declared mutability, which should be equal to the allocation's mutability.
+                    assert_eq!(mutability, alloc.0.mutability);
+                    (alloc.0.size(), alloc.0.align, mutability)
                 } else {
                     // Use size and align of the type for everything else. We need
                     // to do that to
@@ -873,20 +901,20 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                     };
                     (layout.size, layout.align.abi, mutability)
                 };
-                (size, align, AllocKind::LiveData, mutability)
+                AllocInfo::new(size, align, AllocKind::LiveData, mutability)
             }
             Some(GlobalAlloc::Memory(alloc)) => {
                 // Need to duplicate the logic here, because the global allocations have
                 // different associated types than the interpreter-local ones.
                 let alloc = alloc.inner();
-                (alloc.size(), alloc.align, AllocKind::LiveData, alloc.mutability)
+                AllocInfo::new(alloc.size(), alloc.align, AllocKind::LiveData, alloc.mutability)
             }
             Some(GlobalAlloc::Function { .. }) => {
                 bug!("We already checked function pointers above")
             }
             Some(GlobalAlloc::VTable(..)) => {
                 // No data to be accessed here. But vtables are pointer-aligned.
-                return (
+                return AllocInfo::new(
                     Size::ZERO,
                     self.tcx.data_layout.pointer_align.abi,
                     AllocKind::VTable,
@@ -902,7 +930,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                     .dead_alloc_map
                     .get(&id)
                     .expect("deallocated pointers should all be recorded in `dead_alloc_map`");
-                (size, align, AllocKind::Dead, Mutability::Not)
+                AllocInfo::new(size, align, AllocKind::Dead, Mutability::Not)
             }
         }
     }
@@ -913,11 +941,11 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         id: AllocId,
         msg: CheckInAllocMsg,
     ) -> InterpResult<'tcx, (Size, Align)> {
-        let (size, align, kind, _mutbl) = self.get_alloc_info(id);
-        if matches!(kind, AllocKind::Dead) {
+        let info = self.get_alloc_info(id);
+        if matches!(info.kind, AllocKind::Dead) {
             throw_ub!(PointerUseAfterFree(id, msg))
         }
-        interp_ok((size, align))
+        interp_ok((info.size, info.align))
     }
 
     fn get_fn_alloc(&self, id: AllocId) -> Option<FnVal<'tcx, M::ExtraFnVal>> {
@@ -1469,7 +1497,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 let ptr = scalar.to_pointer(self)?;
                 match self.ptr_try_get_alloc_id(ptr, 0) {
                     Ok((alloc_id, offset, _)) => {
-                        let (size, _align, _kind, _mutbl) = self.get_alloc_info(alloc_id);
+                        let size = self.get_alloc_info(alloc_id).size;
                         // If the pointer is out-of-bounds, it may be null.
                         // Note that one-past-the-end (offset == size) is still inbounds, and never null.
                         offset > size

compiler/rustc_const_eval/src/interpret/mod.rs

@@ -31,7 +31,7 @@ pub use self::intern::{
 };
 pub(crate) use self::intrinsics::eval_nullary_intrinsic;
 pub use self::machine::{AllocMap, Machine, MayLeak, ReturnAction, compile_time_machine};
-pub use self::memory::{AllocKind, AllocRef, AllocRefMut, FnVal, Memory, MemoryKind};
+pub use self::memory::{AllocInfo, AllocKind, AllocRef, AllocRefMut, FnVal, Memory, MemoryKind};
 use self::operand::Operand;
 pub use self::operand::{ImmTy, Immediate, OpTy};
 pub use self::place::{MPlaceTy, MemPlaceMeta, PlaceTy, Writeable};

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -29,7 +29,6 @@ use rustc_middle::ty::{self, Ty};
 use rustc_span::symbol::{Symbol, sym};
 use tracing::trace;
 
-use super::machine::AllocMap;
 use super::{
     AllocId, AllocKind, CheckInAllocMsg, GlobalAlloc, ImmTy, Immediate, InterpCx, InterpResult,
     MPlaceTy, Machine, MemPlaceMeta, PlaceTy, Pointer, Projectable, Scalar, ValueVisitor, err_ub,
@@ -594,8 +593,8 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
                     }
 
                     // Dangling and Mutability check.
-                    let (size, _align, alloc_kind, _mutbl) = self.ecx.get_alloc_info(alloc_id);
-                    if alloc_kind == AllocKind::Dead {
+                    let info = self.ecx.get_alloc_info(alloc_id);
+                    if info.kind == AllocKind::Dead {
                         // This can happen for zero-sized references. We can't have *any* references to
                         // non-existing allocations in const-eval though, interning rejects them all as
                         // the rest of rustc isn't happy with them... so we throw an error, even though
@@ -618,7 +617,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
                             }
                         };
                         // Determine what it actually points to.
-                        let alloc_actual_mutbl = mutability(self.ecx, alloc_id);
+                        let alloc_actual_mutbl = info.mutbl;
                         // Mutable pointer to immutable memory is no good.
                         if ptr_expected_mutbl == Mutability::Mut
                             && alloc_actual_mutbl == Mutability::Not
@@ -844,7 +843,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
     fn in_mutable_memory(&self, val: &PlaceTy<'tcx, M::Provenance>) -> bool {
         if let Some(mplace) = val.as_mplace_or_local().left() {
             if let Some(alloc_id) = mplace.ptr().provenance.and_then(|p| p.get_alloc_id()) {
-                mutability(self.ecx, alloc_id).is_mut()
+                self.ecx.get_alloc_info(alloc_id).mutbl.is_mut()
             } else {
                 // No memory at all.
                 false
@@ -1016,53 +1015,6 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
     }
 }
 
-/// Returns whether the allocation is mutable, and whether it's actually a static.
-/// For "root" statics we look at the type to account for interior
-/// mutability; for nested statics we have no type and directly use the annotated mutability.
-fn mutability<'tcx>(ecx: &InterpCx<'tcx, impl Machine<'tcx>>, alloc_id: AllocId) -> Mutability {
-    // Let's see what kind of memory this points to.
-    // We're not using `try_global_alloc` since dangling pointers have already been handled.
-    match ecx.tcx.global_alloc(alloc_id) {
-        GlobalAlloc::Static(did) => {
-            let DefKind::Static { safety: _, mutability, nested } = ecx.tcx.def_kind(did) else {
-                bug!()
-            };
-            if nested {
-                assert!(
-                    ecx.memory.alloc_map.get(alloc_id).is_none(),
-                    "allocations of nested statics are already interned: {alloc_id:?}, {did:?}"
-                );
-                // Nested statics in a `static` are never interior mutable,
-                // so just use the declared mutability.
-                mutability
-            } else {
-                let mutability = match mutability {
-                    Mutability::Not
-                        if !ecx
-                            .tcx
-                            .type_of(did)
-                            .no_bound_vars()
-                            .expect("statics should not have generic parameters")
-                            .is_freeze(*ecx.tcx, ty::ParamEnv::reveal_all()) =>
-                    {
-                        Mutability::Mut
-                    }
-                    _ => mutability,
-                };
-                if let Some((_, alloc)) = ecx.memory.alloc_map.get(alloc_id) {
-                    assert_eq!(alloc.mutability, mutability);
-                }
-                mutability
-            }
-        }
-        GlobalAlloc::Memory(alloc) => alloc.inner().mutability,
-        GlobalAlloc::Function { .. } | GlobalAlloc::VTable(..) => {
-            // These are immutable, we better don't allow mutable pointers here.
-            Mutability::Not
-        }
-    }
-}
-
 impl<'rt, 'tcx, M: Machine<'tcx>> ValueVisitor<'tcx, M> for ValidityVisitor<'rt, 'tcx, M> {
     type V = PlaceTy<'tcx, M::Provenance>;
 

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

@@ -134,7 +134,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 // entered for addresses that are not the base address, so even zero-sized
                 // allocations will get recognized at their base address -- but all other
                 // allocations will *not* be recognized at their "end" address.
-                let size = ecx.get_alloc_info(alloc_id).0;
+                let size = ecx.get_alloc_info(alloc_id).size;
                 if offset < size.bytes() { Some(alloc_id) } else { None }
             }
         }?;
@@ -157,25 +157,25 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
     ) -> InterpResult<'tcx, u64> {
         let ecx = self.eval_context_ref();
         let mut rng = ecx.machine.rng.borrow_mut();
-        let (size, align, kind, _mutbl) = ecx.get_alloc_info(alloc_id);
+        let info = ecx.get_alloc_info(alloc_id);
         // This is either called immediately after allocation (and then cached), or when
         // adjusting `tcx` pointers (which never get freed). So assert that we are looking
         // at a live allocation. This also ensures that we never re-assign an address to an
         // allocation that previously had an address, but then was freed and the address
         // information was removed.
-        assert!(!matches!(kind, AllocKind::Dead));
+        assert!(!matches!(info.kind, AllocKind::Dead));
 
         // This allocation does not have a base address yet, pick or reuse one.
         if ecx.machine.native_lib.is_some() {
             // In native lib mode, we use the "real" address of the bytes for this allocation.
             // This ensures the interpreted program and native code have the same view of memory.
-            let base_ptr = match kind {
+            let base_ptr = match info.kind {
                 AllocKind::LiveData => {
                     if ecx.tcx.try_get_global_alloc(alloc_id).is_some() {
                         // For new global allocations, we always pre-allocate the memory to be able use the machine address directly.
-                        let prepared_bytes = MiriAllocBytes::zeroed(size, align)
+                        let prepared_bytes = MiriAllocBytes::zeroed(info.size, info.align)
                             .unwrap_or_else(|| {
-                                panic!("Miri ran out of memory: cannot create allocation of {size:?} bytes")
+                                panic!("Miri ran out of memory: cannot create allocation of {size:?} bytes", size = info.size)
                             });
                         let ptr = prepared_bytes.as_ptr();
                         // Store prepared allocation space to be picked up for use later.
@@ -204,7 +204,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
         }
         // We are not in native lib mode, so we control the addresses ourselves.
         if let Some((reuse_addr, clock)) =
-            global_state.reuse.take_addr(&mut *rng, size, align, memory_kind, ecx.active_thread())
+            global_state.reuse.take_addr(&mut *rng, info.size, info.align, memory_kind, ecx.active_thread())
         {
             if let Some(clock) = clock {
                 ecx.acquire_clock(&clock);
@@ -220,14 +220,14 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 .next_base_addr
                 .checked_add(slack)
                 .ok_or_else(|| err_exhaust!(AddressSpaceFull))?;
-            let base_addr = align_addr(base_addr, align.bytes());
+            let base_addr = align_addr(base_addr, info.align.bytes());
 
             // Remember next base address.  If this allocation is zero-sized, leave a gap of at
             // least 1 to avoid two allocations having the same base address. (The logic in
             // `alloc_id_from_addr` assumes unique addresses, and different function/vtable pointers
             // need to be distinguishable!)
             global_state.next_base_addr = base_addr
-                .checked_add(max(size.bytes(), 1))
+                .checked_add(max(info.size.bytes(), 1))
                 .ok_or_else(|| err_exhaust!(AddressSpaceFull))?;
             // Even if `Size` didn't overflow, we might still have filled up the address space.
             if global_state.next_base_addr > ecx.target_usize_max() {

src/tools/miri/src/borrow_tracker/mod.rs

@@ -363,7 +363,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             // If it does exist, then we have the guarantee that the
             // pointer is readable, and the implicit read access inserted
             // will never cause UB on the pointer itself.
-            let (_, _, kind, _mutbl) = this.get_alloc_info(*alloc_id);
+            let kind = this.get_alloc_info(*alloc_id).kind;
             if matches!(kind, AllocKind::LiveData) {
                 let alloc_extra = this.get_alloc_extra(*alloc_id)?; // can still fail for `extern static`
                 let alloc_borrow_tracker = &alloc_extra.borrow_tracker.as_ref().unwrap();

src/tools/miri/src/borrow_tracker/stacked_borrows/mod.rs

@@ -626,7 +626,7 @@ trait EvalContextPrivExt<'tcx, 'ecx>: crate::MiriInterpCxExt<'tcx> {
                 return interp_ok(())
             };
 
-            let (_size, _align, alloc_kind, _mutbl) = this.get_alloc_info(alloc_id);
+            let alloc_kind = this.get_alloc_info(alloc_id).kind;
             match alloc_kind {
                 AllocKind::LiveData => {
                     // This should have alloc_extra data, but `get_alloc_extra` can still fail
@@ -1017,7 +1017,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         // Function pointers and dead objects don't have an alloc_extra so we ignore them.
         // This is okay because accessing them is UB anyway, no need for any Stacked Borrows checks.
         // NOT using `get_alloc_extra_mut` since this might be a read-only allocation!
-        let (_size, _align, kind, _mutbl) = this.get_alloc_info(alloc_id);
+        let kind = this.get_alloc_info(alloc_id).kind;
         match kind {
             AllocKind::LiveData => {
                 // This should have alloc_extra data, but `get_alloc_extra` can still fail

src/tools/miri/src/borrow_tracker/tree_borrows/mod.rs

@@ -274,7 +274,7 @@ trait EvalContextPrivExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 .insert(new_tag, protect);
         }
 
-        let alloc_kind = this.get_alloc_info(alloc_id).2;
+        let alloc_kind = this.get_alloc_info(alloc_id).kind;
         if !matches!(alloc_kind, AllocKind::LiveData) {
             assert_eq!(ptr_size, Size::ZERO); // we did the deref check above, size has to be 0 here
             // There's not actually any bytes here where accesses could even be tracked.
@@ -538,7 +538,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         // Function pointers and dead objects don't have an alloc_extra so we ignore them.
         // This is okay because accessing them is UB anyway, no need for any Tree Borrows checks.
         // NOT using `get_alloc_extra_mut` since this might be a read-only allocation!
-        let (_size, _align, kind, _mutbl) = this.get_alloc_info(alloc_id);
+        let kind = this.get_alloc_info(alloc_id).kind;
         match kind {
             AllocKind::LiveData => {
                 // This should have alloc_extra data, but `get_alloc_extra` can still fail