fix for infallible allocation

README.md

@@ -90,15 +90,15 @@ things (like adding support for a new intrinsic) can be done by working just on
 the miri side.
 
 To prepare, make sure you are using a nightly Rust compiler.  You also need to
-set up a libstd that enables execution with miri:
+set up a libstd that enables execution with Miri:
 
 ```sh
 rustup override set nightly # or the nightly in `rust-version`
 cargo run --bin cargo-miri -- miri setup
 ```
 
 The last command should end in printing the directory where the libstd was
-built.  Set that as your MIRI_SYSROOT environment variable:
+built.  Set that as your `MIRI_SYSROOT` environment variable:
 
 ```sh
 export MIRI_SYSROOT=~/.cache/miri/HOST # or whatever the previous command said
@@ -109,7 +109,7 @@ export MIRI_SYSROOT=~/.cache/miri/HOST # or whatever the previous command said
 Now you can run Miri directly, without going through `cargo miri`:
 
 ```sh
-cargo run tests/run-pass-fullmir/format.rs # or whatever test you like
+cargo run tests/run-pass/format.rs # or whatever test you like
 ```
 
 You can also run the test suite with `cargo test --release`.  `cargo test
@@ -120,14 +120,33 @@ less time.
 
 Now you are set up!  You can write a failing test case, and tweak miri until it
 fails no more.
+You can get a trace of which MIR statements are being executed by setting the
+`MIRI_LOG` environment variable.  For example:
+
+```sh
+MIRI_LOG=info cargo run tests/run-pass/vecs.rs
+```
+
+Setting `MIRI_LOG` like this will configure logging for miri itself as well as
+the `rustc::mir::interpret` and `rustc_mir::interpret` modules in rustc.  You
+can also do more targeted configuration, e.g. to debug the stacked borrows
+implementation:
+```sh
+MIRI_LOG=rustc_mir::interpret=info,miri::stacked_borrows cargo run tests/run-pass/vecs.rs
+```
+
+In addition, you can set `MIRI_BACKTRACE=1` to get a backtrace of where an
+evaluation error was originally created.
+
 
 ### Using a locally built rustc
 
 Since the heart of Miri (the main interpreter engine) lives in rustc, working on
 Miri will often require using a locally built rustc.  The bug you want to fix
 may actually be on the rustc side, or you just need to get more detailed trace
-of the execution -- in both cases, you should develop miri against a rustc you
-compiled yourself, with debug assertions (and hence tracing) enabled.
+of the execution than what is possible with release builds -- in both cases, you
+should develop miri against a rustc you compiled yourself, with debug assertions
+(and hence tracing) enabled.
 
 The setup for a local rustc works as follows:
 ```sh
@@ -149,22 +168,6 @@ rustup override set custom
 With this, you should now have a working development setup!  See
 ["Testing Miri"](#testing-miri) above for how to proceed.
 
-Moreover, you can now run Miri with a trace of all execution steps:
-```sh
-MIRI_LOG=debug cargo run tests/run-pass/vecs.rs
-```
-
-Setting `MIRI_LOG` like this will configure logging for miri itself as well as
-the `rustc::mir::interpret` and `rustc_mir::interpret` modules in rustc.  You
-can also do more targeted configuration, e.g. to debug the stacked borrows
-implementation:
-```sh
-MIRI_LOG=rustc_mir::interpret=debug,miri::stacked_borrows cargo run tests/run-pass/vecs.rs
-```
-
-In addition, you can set `MIRI_BACKTRACE=1` to get a backtrace of where an
-evaluation error was originally created.
-
 ### Miri `-Z` flags and environment variables
 
 Several `-Z` flags are relevant for Miri:

rust-version

@@ -1 +1 @@
-nightly-2018-12-22
+nightly-2018-12-24

src/fn_call.rs

@@ -84,7 +84,7 @@ pub trait EvalContextExt<'a, 'mir, 'tcx: 'a+'mir>: crate::MiriEvalContextExt<'a,
                     this.write_null(dest)?;
                 } else {
                     let align = this.tcx.data_layout.pointer_align.abi;
-                    let ptr = this.memory_mut().allocate(Size::from_bytes(size), align, MiriMemoryKind::C.into())?;
+                    let ptr = this.memory_mut().allocate(Size::from_bytes(size), align, MiriMemoryKind::C.into());
                     this.write_scalar(Scalar::Ptr(ptr.with_default_tag()), dest)?;
                 }
             }
@@ -114,7 +114,7 @@ pub trait EvalContextExt<'a, 'mir, 'tcx: 'a+'mir>: crate::MiriEvalContextExt<'a,
                         Size::from_bytes(size),
                         Align::from_bytes(align).unwrap(),
                         MiriMemoryKind::Rust.into()
-                    )?
+                    )
                     .with_default_tag();
                 this.write_scalar(Scalar::Ptr(ptr), dest)?;
             }
@@ -132,7 +132,7 @@ pub trait EvalContextExt<'a, 'mir, 'tcx: 'a+'mir>: crate::MiriEvalContextExt<'a,
                         Size::from_bytes(size),
                         Align::from_bytes(align).unwrap(),
                         MiriMemoryKind::Rust.into()
-                    )?
+                    )
                     .with_default_tag();
                 this.memory_mut()
                     .get_mut(ptr.alloc_id)?
@@ -358,7 +358,7 @@ pub trait EvalContextExt<'a, 'mir, 'tcx: 'a+'mir>: crate::MiriEvalContextExt<'a,
                         Size::from_bytes((value.len() + 1) as u64),
                         Align::from_bytes(1).unwrap(),
                         MiriMemoryKind::Env.into(),
-                    )?.with_default_tag();
+                    ).with_default_tag();
                     {
                         let alloc = this.memory_mut().get_mut(value_copy.alloc_id)?;
                         alloc.write_bytes(tcx, value_copy, &value)?;

src/lib.rs

@@ -101,7 +101,7 @@ pub fn create_ecx<'a, 'mir: 'a, 'tcx: 'mir>(
 
     // Return value (in static memory so that it does not count as leak)
     let ret = ecx.layout_of(start_mir.return_ty())?;
-    let ret_ptr = ecx.allocate(ret, MiriMemoryKind::MutStatic.into())?;
+    let ret_ptr = ecx.allocate(ret, MiriMemoryKind::MutStatic.into());
 
     // Push our stack frame
     ecx.push_stack_frame(
@@ -125,7 +125,7 @@ pub fn create_ecx<'a, 'mir: 'a, 'tcx: 'mir>(
     ecx.write_scalar(argc, dest)?;
     // Store argc for macOS _NSGetArgc
     {
-        let argc_place = ecx.allocate(dest.layout, MiriMemoryKind::Env.into())?;
+        let argc_place = ecx.allocate(dest.layout, MiriMemoryKind::Env.into());
         ecx.write_scalar(argc, argc_place.into())?;
         ecx.machine.argc = Some(argc_place.ptr.to_ptr()?);
     }
@@ -136,14 +136,14 @@ pub fn create_ecx<'a, 'mir: 'a, 'tcx: 'mir>(
     let dest = ecx.eval_place(&mir::Place::Local(args.next().unwrap()))?;
     let cmd = ecx.memory_mut().allocate_static_bytes(CMD.as_bytes()).with_default_tag();
     let raw_str_layout = ecx.layout_of(ecx.tcx.mk_imm_ptr(ecx.tcx.types.u8))?;
-    let cmd_place = ecx.allocate(raw_str_layout, MiriMemoryKind::Env.into())?;
+    let cmd_place = ecx.allocate(raw_str_layout, MiriMemoryKind::Env.into());
     ecx.write_scalar(Scalar::Ptr(cmd), cmd_place.into())?;
     ecx.memory_mut().mark_immutable(cmd_place.to_ptr()?.alloc_id)?;
     // Store argv for macOS _NSGetArgv
     {
         let argv = cmd_place.ptr;
         ecx.write_scalar(argv, dest)?;
-        let argv_place = ecx.allocate(dest.layout, MiriMemoryKind::Env.into())?;
+        let argv_place = ecx.allocate(dest.layout, MiriMemoryKind::Env.into());
         ecx.write_scalar(argv, argv_place.into())?;
         ecx.machine.argv = Some(argv_place.ptr.to_ptr()?);
     }
@@ -155,7 +155,7 @@ pub fn create_ecx<'a, 'mir: 'a, 'tcx: 'mir>(
             Size::from_bytes(cmd_utf16.len() as u64 * 2),
             Align::from_bytes(2).unwrap(),
             MiriMemoryKind::Env.into(),
-        )?.with_default_tag();
+        ).with_default_tag();
         ecx.machine.cmd_line = Some(cmd_ptr);
         // store the UTF-16 string
         let char_size = Size::from_bytes(2);
@@ -516,13 +516,13 @@ impl<'a, 'mir, 'tcx> Machine<'a, 'mir, 'tcx> for Evaluator<'tcx> {
         ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
         ptr: Pointer,
         kind: MemoryKind<Self::MemoryKinds>,
-    ) -> EvalResult<'tcx, Pointer<Borrow>> {
+    ) -> Pointer<Borrow> {
         if !ecx.machine.validate {
             // No tracking
-            Ok(ptr.with_default_tag())
+            ptr.with_default_tag()
         } else {
             let tag = ecx.tag_new_allocation(ptr.alloc_id, kind);
-            Ok(Pointer::new_with_tag(ptr.alloc_id, ptr.offset, tag))
+            Pointer::new_with_tag(ptr.alloc_id, ptr.offset, tag)
         }
     }