add a Miri extern fn to mark an allocation as being a static root for leak checking

Author: RalfJung

src/eval.rs

@@ -5,6 +5,7 @@ use std::ffi::OsStr;
 
 use rand::rngs::StdRng;
 use rand::SeedableRng;
+use log::info;
 
 use rustc_hir::def_id::DefId;
 use rustc_middle::ty::{self, layout::LayoutCx, TyCtxt};
@@ -195,8 +196,8 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
 /// Returns `Some(return_code)` if program executed completed.
 /// Returns `None` if an evaluation error occured.
 pub fn eval_main<'tcx>(tcx: TyCtxt<'tcx>, main_id: DefId, config: MiriConfig) -> Option<i64> {
-    // FIXME: on Windows, we ignore leaks (https://github.com/rust-lang/miri/issues/1302).
-    let ignore_leaks = config.ignore_leaks || tcx.sess.target.target.target_os == "windows";
+    // Copy setting before we move `config`.
+    let ignore_leaks = config.ignore_leaks;
 
     let (mut ecx, ret_place) = match create_ecx(tcx, main_id, config) {
         Ok(v) => v,
@@ -244,7 +245,8 @@ pub fn eval_main<'tcx>(tcx: TyCtxt<'tcx>, main_id: DefId, config: MiriConfig) ->
     match res {
         Ok(return_code) => {
             if !ignore_leaks {
-                let leaks = ecx.memory.leak_report();
+                info!("Additonal static roots: {:?}", ecx.machine.static_roots);
+                let leaks = ecx.memory.leak_report(&ecx.machine.static_roots);
                 if leaks != 0 {
                     tcx.sess.err("the evaluated program leaked memory");
                     // Ignore the provided return code - let the reported error

src/machine.rs

@@ -262,6 +262,9 @@ pub struct Evaluator<'mir, 'tcx> {
 
     /// Precomputed `TyLayout`s for primitive data types that are commonly used inside Miri.
     pub(crate) layouts: PrimitiveLayouts<'tcx>,
+
+    /// Allocations that are considered roots of static memory (that may leak).
+    pub(crate) static_roots: Vec<AllocId>,
 }
 
 impl<'mir, 'tcx> Evaluator<'mir, 'tcx> {
@@ -289,6 +292,7 @@ impl<'mir, 'tcx> Evaluator<'mir, 'tcx> {
             time_anchor: Instant::now(),
             layouts,
             threads: ThreadManager::default(),
+            static_roots: Vec::new(),
         }
     }
 }

src/shims/foreign_items.rs

@@ -197,6 +197,17 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         // Here we dispatch all the shims for foreign functions. If you have a platform specific
         // shim, add it to the corresponding submodule.
         match link_name {
+            // Miri-specific extern functions
+            "miri_static_root" => {
+                let &[ptr] = check_arg_count(args)?;
+                let ptr = this.read_scalar(ptr)?.not_undef()?;
+                let ptr = this.force_ptr(ptr)?;
+                if ptr.offset != Size::ZERO {
+                    throw_unsup_format!("Pointer passed to miri_static_root must point to beginning of an allocated block");
+                }
+                this.machine.static_roots.push(ptr.alloc_id);
+            }
+
             // Standard C allocation
             "malloc" => {
                 let &[size] = check_arg_count(args)?;