Hold the state

src/interpreter/iterator.rs

@@ -0,0 +1,92 @@
+use super::{
+    FnEvalContext,
+    CachedMir,
+    TerminatorTarget,
+};
+use error::EvalResult;
+use rustc::mir::repr as mir;
+
+pub enum Event<'a, 'tcx: 'a> {
+    Assignment(&'a mir::Statement<'tcx>),
+    Terminator(&'a mir::Terminator<'tcx>),
+    Done,
+}
+
+pub struct Stepper<'fncx, 'a: 'fncx, 'b: 'a + 'mir, 'mir: 'fncx, 'tcx: 'b>{
+    fncx: &'fncx mut FnEvalContext<'a, 'b, 'mir, 'tcx>,
+    block: mir::BasicBlock,
+    stmt: usize,
+    mir: CachedMir<'mir, 'tcx>,
+    process: fn (&mut Stepper<'fncx, 'a, 'b, 'mir, 'tcx>) -> EvalResult<()>,
+}
+
+impl<'fncx, 'a, 'b: 'a + 'mir, 'mir, 'tcx: 'b> Stepper<'fncx, 'a, 'b, 'mir, 'tcx> {
+    pub(super) fn new(fncx: &'fncx mut FnEvalContext<'a, 'b, 'mir, 'tcx>) -> Self {
+        Stepper {
+            block: fncx.frame().next_block,
+            mir: fncx.mir(),
+            fncx: fncx,
+            stmt: 0,
+            process: Self::dummy,
+        }
+    }
+    fn dummy(&mut self) -> EvalResult<()> { Ok(()) }
+    fn statement(&mut self) -> EvalResult<()> {
+        let block_data = self.mir.basic_block_data(self.block);
+        let stmt = &block_data.statements[self.stmt];
+        let mir::StatementKind::Assign(ref lvalue, ref rvalue) = stmt.kind;
+        let result = self.fncx.eval_assignment(lvalue, rvalue);
+        self.fncx.maybe_report(stmt.span, result)?;
+        self.stmt += 1;
+        Ok(())
+    }
+    fn terminator(&mut self) -> EvalResult<()> {
+        self.stmt = 0;
+        let term = {
+            let block_data = self.mir.basic_block_data(self.block);
+            let terminator = block_data.terminator();
+            let result = self.fncx.eval_terminator(terminator);
+            self.fncx.maybe_report(terminator.span, result)?
+        };
+        match term {
+            TerminatorTarget::Block(block) => {
+                self.block = block;
+            },
+            TerminatorTarget::Return => {
+                self.fncx.pop_stack_frame();
+                self.fncx.name_stack.pop();
+                if !self.fncx.stack.is_empty() {
+                    self.block = self.fncx.frame().next_block;
+                    self.mir = self.fncx.mir();
+                }
+            },
+            TerminatorTarget::Call => {
+                self.block = self.fncx.frame().next_block;
+                self.mir = self.fncx.mir();
+            },
+        }
+        Ok(())
+    }
+    pub fn step<'step>(&'step mut self) -> EvalResult<Event<'step, 'tcx>> {
+        (self.process)(self)?;
+
+        if self.fncx.stack.is_empty() {
+            // fuse the iterator
+            self.process = Self::dummy;
+            return Ok(Event::Done);
+        }
+
+        let basic_block = self.mir.basic_block_data(self.block);
+
+        if let Some(stmt) = basic_block.statements.get(self.stmt) {
+            self.process = Self::statement;
+            return Ok(Event::Assignment(&stmt));
+        }
+
+        self.process = Self::terminator;
+        Ok(Event::Terminator(basic_block.terminator()))
+    }
+    pub fn block(&self) -> mir::BasicBlock {
+        self.block
+    }
+}

src/interpreter.rs → src/interpreter/mod.rs

@@ -20,6 +20,8 @@ use error::{EvalError, EvalResult};
 use memory::{Memory, Pointer};
 use primval::{self, PrimVal};
 
+mod iterator;
+
 struct GlobalEvalContext<'a, 'tcx: 'a> {
     /// The results of the type checker, from rustc.
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
@@ -135,6 +137,23 @@ impl<'a, 'tcx> GlobalEvalContext<'a, 'tcx> {
             name_stack: Vec::new(),
         }
     }
+
+    fn call(&mut self, mir: &mir::Mir<'tcx>) -> EvalResult<Option<Pointer>> {
+        let mut nested_fecx = FnEvalContext::new(self);
+
+        let return_ptr = match mir.return_ty {
+            ty::FnConverging(ty) => {
+                let size = nested_fecx.type_size(ty);
+                Some(nested_fecx.memory.allocate(size))
+            }
+            ty::FnDiverging => None,
+        };
+
+        let substs = nested_fecx.substs();
+        nested_fecx.push_stack_frame(CachedMir::Ref(mir), substs, return_ptr);
+        nested_fecx.run()?;
+        Ok(return_ptr)
+    }
 }
 
 impl<'a, 'b, 'mir, 'tcx> FnEvalContext<'a, 'b, 'mir, 'tcx> {
@@ -167,55 +186,22 @@ impl<'a, 'b, 'mir, 'tcx> FnEvalContext<'a, 'b, 'mir, 'tcx> {
     }
 
     fn run(&mut self) -> EvalResult<()> {
-        'outer: while !self.stack.is_empty() {
-            let mut current_block = self.frame().next_block;
+        let mut stepper = iterator::Stepper::new(self);
+        'outer: loop {
+            use self::iterator::Event::*;
+            trace!("// {:?}", stepper.block());
 
             loop {
-                trace!("// {:?}", current_block);
-                let current_mir = self.mir().clone(); // Cloning a reference.
-                let block_data = current_mir.basic_block_data(current_block);
-
-                for stmt in &block_data.statements {
-                    trace!("{:?}", stmt);
-                    let mir::StatementKind::Assign(ref lvalue, ref rvalue) = stmt.kind;
-                    let result = self.eval_assignment(lvalue, rvalue);
-                    self.maybe_report(stmt.span, result)?;
-                }
-
-                let terminator = block_data.terminator();
-                trace!("{:?}", terminator.kind);
-
-                let result = self.eval_terminator(terminator);
-                match self.maybe_report(terminator.span, result)? {
-                    TerminatorTarget::Block(block) => current_block = block,
-                    TerminatorTarget::Return => {
-                        self.pop_stack_frame();
-                        self.name_stack.pop();
+                match stepper.step()? {
+                    Assignment(statement) => trace!("{:?}", statement),
+                    Terminator(terminator) => {
+                        trace!("{:?}", terminator.kind);
                         continue 'outer;
-                    }
-                    TerminatorTarget::Call => continue 'outer,
+                    },
+                    Done => return Ok(()),
                 }
             }
         }
-
-        Ok(())
-    }
-
-    fn call_nested(&mut self, mir: &mir::Mir<'tcx>) -> EvalResult<Option<Pointer>> {
-        let mut nested_fecx = FnEvalContext::new(self.gecx);
-
-        let return_ptr = match mir.return_ty {
-            ty::FnConverging(ty) => {
-                let size = nested_fecx.type_size(ty);
-                Some(nested_fecx.memory.allocate(size))
-            }
-            ty::FnDiverging => None,
-        };
-
-        let substs = nested_fecx.substs();
-        nested_fecx.push_stack_frame(CachedMir::Ref(mir), substs, return_ptr);
-        nested_fecx.run()?;
-        Ok(return_ptr)
     }
 
     fn push_stack_frame(&mut self, mir: CachedMir<'mir, 'tcx>, substs: &'tcx Substs<'tcx>,
@@ -996,13 +982,13 @@ impl<'a, 'b, 'mir, 'tcx> FnEvalContext<'a, 'b, 'mir, 'tcx> {
                 use rustc::mir::repr::Literal::*;
                 match *literal {
                     Value { ref value } => Ok(self.const_to_ptr(value)?),
-                    Item { .. } => unimplemented!(),
+                    Item { .. } => Err(EvalError::Unimplemented(format!("function pointers are unimplemented"))),
                     Promoted { index } => {
                         // TODO(solson): Mark constants and statics as read-only and cache their
                         // values.
                         let current_mir = self.mir();
                         let mir = &current_mir.promoted[index];
-                        self.call_nested(mir).map(Option::unwrap)
+                        self.gecx.call(mir).map(Option::unwrap)
                     }
                 }
             }
@@ -1021,7 +1007,7 @@ impl<'a, 'b, 'mir, 'tcx> FnEvalContext<'a, 'b, 'mir, 'tcx> {
             Static(def_id) => {
                 // TODO(solson): Mark constants and statics as read-only and cache their values.
                 let mir = self.load_mir(def_id);
-                self.call_nested(&mir)?.unwrap()
+                self.gecx.call(&mir)?.unwrap()
             }
 
             Projection(ref proj) => {
@@ -1426,10 +1412,9 @@ pub fn interpret_start_points<'a, 'tcx>(
                 debug!("Interpreting: {}", item.name);
 
                 let mut gecx = GlobalEvalContext::new(tcx, mir_map);
-                let mut fecx = FnEvalContext::new(&mut gecx);
-                match fecx.call_nested(mir) {
+                match gecx.call(mir) {
                     Ok(Some(return_ptr)) => if log_enabled!(::log::LogLevel::Debug) {
-                        fecx.memory.dump(return_ptr.alloc_id);
+                        gecx.memory.dump(return_ptr.alloc_id);
                     },
                     Ok(None) => warn!("diverging function returned"),
                     Err(_e) => {

src/lib.rs

@@ -6,6 +6,7 @@
     filling_drop,
     question_mark,
     rustc_private,
+    pub_restricted,
 )]
 
 // From rustc.

tests/compile-fail/unimplemented.rs

@@ -0,0 +1,16 @@
+#![feature(custom_attribute)]
+#![allow(dead_code, unused_attributes)]
+
+//error-pattern:function pointers are unimplemented
+
+static mut X: usize = 5;
+
+#[miri_run]
+fn static_mut() {
+    unsafe {
+        X = 6;
+        assert_eq!(X, 6);
+    }
+}
+
+fn main() {}