Auto merge of #1019 - RalfJung:rustup, r=RalfJung

rustup: more flexible write_bytes

avoids allocations and removes itertools dependency

Author: bors

Cargo.lock

@@ -40,7 +40,6 @@ log = "0.4"
 shell-escape = "0.1.4"
 hex = "0.3.2"
 rand = "0.7"
-itertools = "0.8"
 
 # A noop dependency that changes in the Rust repository, it's a bit of a hack.
 # See the `src/tools/rustc-workspace-hack/README.md` file in `rust-lang/rust`

Cargo.toml

@@ -1 +1 @@
-f466f52c1bf8f2e4454e31c683a88625ad4b4033
+55e00631e5bc5b16d40232914e57deeea197a8e4

rust-version

@@ -1,4 +1,4 @@
-use std::mem;
+use std::{mem, iter};
 use std::ffi::{OsStr, OsString};
 
 use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX};
@@ -379,7 +379,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 _ => throw_unsup_format!("The {} error cannot be transformed into a raw os error", e)
             })?
         } else {
-            // FIXME: we have to implement the windows' equivalent of this.
+            // FIXME: we have to implement the Windows equivalent of this.
             throw_unsup_format!("Setting the last OS error from an io::Error is unsupported for {}.", target.target_os)
         };
         this.set_last_error(last_error)
@@ -390,7 +390,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
     /// `Ok(-1)` and sets the last OS error accordingly.
     ///
     /// This function uses `T: From<i32>` instead of `i32` directly because some IO related
-    /// functions return different integer types (like `read`, that returns an `i64`)
+    /// functions return different integer types (like `read`, that returns an `i64`).
     fn try_unwrap_io_result<T: From<i32>>(
         &mut self,
         result: std::io::Result<T>,
@@ -423,12 +423,11 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
     ) -> InterpResult<'tcx, bool> {
         let bytes = os_str_to_bytes(os_str)?;
         // If `size` is smaller or equal than `bytes.len()`, writing `bytes` plus the required null
-        // terminator to memory using the `ptr` pointer would cause an overflow.
+        // terminator to memory using the `ptr` pointer would cause an out-of-bounds access.
         if size <= bytes.len() as u64 {
             return Ok(false);
         }
-        // FIXME: We should use `Iterator::chain` instead when rust-lang/rust#65704 lands.
-        self.eval_context_mut().memory.write_bytes(scalar, [bytes, &[0]].concat())?;
+        self.eval_context_mut().memory.write_bytes(scalar, bytes.iter().copied().chain(iter::once(0u8)))?;
         Ok(true)
     }
 }

src/helpers.rs

@@ -1,3 +1,5 @@
+use std::convert::TryFrom;
+
 use rustc::ty::{Ty, layout::LayoutOf};
 use rustc::mir;
 
@@ -117,8 +119,7 @@ impl<'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'mir, 'tcx> {
         pointee_ty: Ty<'tcx>,
         offset: i64,
     ) -> InterpResult<'tcx, Scalar<Tag>> {
-        // FIXME: assuming here that type size is less than `i64::max_value()`.
-        let pointee_size = self.layout_of(pointee_ty)?.size.bytes() as i64;
+        let pointee_size = i64::try_from(self.layout_of(pointee_ty)?.size.bytes()).unwrap();
         let offset = offset
             .checked_mul(pointee_size)
             .ok_or_else(|| err_panic!(Overflow(mir::BinOp::Mul)))?;

src/operator.rs

@@ -1,4 +1,4 @@
-use std::convert::TryInto;
+use std::{iter, convert::TryInto};
 
 use rustc::hir::def_id::DefId;
 use rustc::mir;
@@ -52,7 +52,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             if zero_init {
                 // We just allocated this, the access is definitely in-bounds.
                 this.memory
-                    .write_bytes(ptr.into(), itertools::repeat_n(0u8, size as usize))
+                    .write_bytes(ptr.into(), iter::repeat(0u8).take(size as usize))
                     .unwrap();
             }
             Scalar::Ptr(ptr)
@@ -227,7 +227,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 );
                 // We just allocated this, the access is definitely in-bounds.
                 this.memory
-                    .write_bytes(ptr.into(), itertools::repeat_n(0u8, size as usize))
+                    .write_bytes(ptr.into(), iter::repeat(0u8).take(size as usize))
                     .unwrap();
                 this.write_scalar(Scalar::Ptr(ptr), dest)?;
             }
@@ -839,7 +839,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 let system_info = this.deref_operand(args[0])?;
                 // Initialize with `0`.
                 this.memory
-                    .write_bytes(system_info.ptr, itertools::repeat_n(0, system_info.layout.size.bytes() as usize))?;
+                    .write_bytes(system_info.ptr, iter::repeat(0u8).take(system_info.layout.size.bytes() as usize))?;
                 // Set number of processors.
                 let dword_size = Size::from_bytes(4);
                 let num_cpus = this.mplace_field(system_info, 6)?;

src/shims/foreign_items.rs

@@ -95,7 +95,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             throw_unsup_format!("unsupported flags {:#x}", flag & !mirror);
         }
 
-        let path: std::path::PathBuf = this.read_os_string_from_c_string(this.read_scalar(path_op)?.not_undef()?)?.into();
+        let path = this.read_os_string_from_c_string(this.read_scalar(path_op)?.not_undef()?)?;
 
         let fd = options.open(path).map(|file| {
             let mut fh = &mut this.machine.file_handler;

src/shims/fs.rs

@@ -1,3 +1,5 @@
+use std::iter;
+
 use rustc_apfloat::Float;
 use rustc::mir;
 use rustc::mir::interpret::{InterpResult, PointerArithmetic};
@@ -357,7 +359,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                             // Do it in memory
                             let mplace = this.force_allocation(dest)?;
                             mplace.meta.unwrap_none(); // must be sized
-                            this.memory.write_bytes(mplace.ptr, itertools::repeat_n(0, dest.layout.size.bytes() as usize))?;
+                            this.memory.write_bytes(mplace.ptr, iter::repeat(0u8).take(dest.layout.size.bytes() as usize))?;
                         }
                     }
                 }
@@ -562,7 +564,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 let ptr = this.read_scalar(args[0])?.not_undef()?;
                 let count = this.read_scalar(args[2])?.to_usize(this)?;
                 let byte_count = ty_layout.size * count;
-                this.memory.write_bytes(ptr, itertools::repeat_n(val_byte, byte_count.bytes() as usize))?;
+                this.memory.write_bytes(ptr, iter::repeat(val_byte).take(byte_count.bytes() as usize))?;
             }
 
             name => throw_unsup_format!("unimplemented intrinsic: {}", name),