Prevent stack overflow for deeply recursive code

rust-lang · Centril · Dec 30, 2019 · Feb 13, 2020 · Mar 8, 2020 · Mar 8, 2020
commit 548b182cf30779b9fa9a159f61c61071c241b492
diff --git a/Cargo.lock b/Cargo.lock
@@ -2580,6 +2580,15 @@ dependencies = [
  "core",
 ]
 
+[[package]]
+name = "psm"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b14fc68b454f875abc8354c2555e1d56596f74833ddc0f77f87f4871ed6a30e0"
+dependencies = [
+ "cc",
+]
+
 [[package]]
 name = "publicsuffix"
 version = "1.5.3"
@@ -3123,6 +3132,7 @@ dependencies = [
  "scoped-tls",
  "serialize",
  "smallvec 1.0.0",
+ "stacker",
 ]
 
 [[package]]
@@ -4542,6 +4552,19 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ffbc596e092fe5f598b12ef46cc03754085ac2f4d8c739ad61c4ae266cc3b3fa"
 
+[[package]]
+name = "stacker"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d96fc4f13a0ac088e9a3cd9af1cc8c5cc1ab5deb2145cef661267dfc9c542f8a"
+dependencies = [
+ "cc",
+ "cfg-if",
+ "libc",
+ "psm",
+ "winapi 0.3.8",
+]
+
 [[package]]
 name = "std"
 version = "0.0.0"

diff --git a/src/librustc/Cargo.toml b/src/librustc/Cargo.toml
@@ -36,3 +36,4 @@ byteorder = { version = "1.3" }
 smallvec = { version = "1.0", features = ["union", "may_dangle"] }
 measureme = "0.7.1"
 rustc_session = { path = "../librustc_session" }
+stacker = "0.1.6"
diff --git a/src/librustc/middle/limits.rs b/src/librustc/middle/limits.rs
@@ -13,6 +13,24 @@ use rustc_span::symbol::{sym, Symbol};
 
 use rustc_data_structures::sync::Once;
 
+// This is the amount of bytes that need to be left on the stack before increasing the size.
+// It must be at least as large as the stack required by any code that does not call
+// `ensure_sufficient_stack`.
+const RED_ZONE: usize = 100 * 1024; // 100k
+
+// Ony the first stack that is pushed, grows exponentially (2^n * STACK_PER_RECURSION) from then
+// on. This flag has performance relevant characteristics. Don't set it too high.
+const STACK_PER_RECURSION: usize = 1 * 1024 * 1024; // 1MB
+
+/// Grows the stack on demand to prevent stack overflow. Call this in strategic locations
+/// to "break up" recursive calls. E.g. almost any call to `visit_expr` or equivalent can benefit
+/// from this.
+///
+/// Should not be sprinkled around carelessly, as it causes a little bit of overhead.
+pub fn ensure_sufficient_stack<R, F: FnOnce() -> R>(f: F) -> R {
+    stacker::maybe_grow(RED_ZONE, STACK_PER_RECURSION, f)
+}
+
 pub fn update_limits(sess: &Session, krate: &ast::Crate) {
     update_limit(sess, krate, &sess.recursion_limit, sym::recursion_limit, 128);
     update_limit(sess, krate, &sess.type_length_limit, sym::type_length_limit, 1048576);

diff --git a/src/librustc/ty/inhabitedness/mod.rs b/src/librustc/ty/inhabitedness/mod.rs
@@ -1,5 +1,6 @@
 pub use self::def_id_forest::DefIdForest;
 
+use crate::middle::limits::ensure_sufficient_stack;
 use crate::ty;
 use crate::ty::context::TyCtxt;
 use crate::ty::TyKind::*;
@@ -196,7 +197,9 @@ impl<'tcx> TyS<'tcx> {
     /// Calculates the forest of `DefId`s from which this type is visibly uninhabited.
     fn uninhabited_from(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> DefIdForest {
         match self.kind {
-            Adt(def, substs) => def.uninhabited_from(tcx, substs, param_env),
+            Adt(def, substs) => {
+                ensure_sufficient_stack(|| def.uninhabited_from(tcx, substs, param_env))
+            }
 
             Never => DefIdForest::full(tcx),
 

diff --git a/src/librustc/ty/query/plumbing.rs b/src/librustc/ty/query/plumbing.rs
@@ -321,7 +321,9 @@ impl<'tcx> TyCtxt<'tcx> {
             };
 
             // Use the `ImplicitCtxt` while we execute the query.
-            tls::enter_context(&new_icx, |_| compute(self))
+            tls::enter_context(&new_icx, |_| {
+                crate::middle::limits::ensure_sufficient_stack(|| compute(self))
+            })
         })
     }
 

diff --git a/src/librustc_ast_lowering/expr.rs b/src/librustc_ast_lowering/expr.rs
@@ -1,6 +1,7 @@
 use super::{ImplTraitContext, LoweringContext, ParamMode, ParenthesizedGenericArgs};
 
 use rustc::bug;
+use rustc::middle::limits::ensure_sufficient_stack;
 use rustc_ast::ast::*;
 use rustc_ast::attr;
 use rustc_ast::ptr::P as AstP;
@@ -22,6 +23,37 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     pub(super) fn lower_expr_mut(&mut self, e: &Expr) -> hir::Expr<'hir> {
         let kind = match e.kind {
+            ExprKind::Paren(ref ex) => {
+                let mut ex = self.lower_expr_mut(ex);
+                // Include parens in span, but only if it is a super-span.
+                if e.span.contains(ex.span) {
+                    ex.span = e.span;
+                }
+                // Merge attributes into the inner expression.
+                let mut attrs = e.attrs.clone();
+                attrs.extend::<Vec<_>>(ex.attrs.into());
+                ex.attrs = attrs;
+                return ex;
+            }
+
+            // Desugar `ExprForLoop`
+            // from: `[opt_ident]: for <pat> in <head> <body>`
+            ExprKind::ForLoop(ref pat, ref head, ref body, opt_label) => {
+                return self.lower_expr_for(e, pat, head, body, opt_label);
+            }
+            _ => ensure_sufficient_stack(|| self.lower_expr_kind(e)),
+        };
+
+        hir::Expr {
+            hir_id: self.lower_node_id(e.id),
+            kind,
+            span: e.span,
+            attrs: e.attrs.iter().map(|a| self.lower_attr(a)).collect::<Vec<_>>().into(),
+        }
+    }
+
+    fn lower_expr_kind(&mut self, e: &Expr) -> hir::ExprKind<'hir> {
+        match e.kind {
             ExprKind::Box(ref inner) => hir::ExprKind::Box(self.lower_expr(inner)),
             ExprKind::Array(ref exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)),
             ExprKind::Repeat(ref expr, ref count) => {
@@ -175,37 +207,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     maybe_expr,
                 )
             }
-            ExprKind::Paren(ref ex) => {
-                let mut ex = self.lower_expr_mut(ex);
-                // Include parens in span, but only if it is a super-span.
-                if e.span.contains(ex.span) {
-                    ex.span = e.span;
-                }
-                // Merge attributes into the inner expression.
-                let mut attrs = e.attrs.clone();
-                attrs.extend::<Vec<_>>(ex.attrs.into());
-                ex.attrs = attrs;
-                return ex;
-            }
-
             ExprKind::Yield(ref opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()),
-
             ExprKind::Err => hir::ExprKind::Err,
-
-            // Desugar `ExprForLoop`
-            // from: `[opt_ident]: for <pat> in <head> <body>`
-            ExprKind::ForLoop(ref pat, ref head, ref body, opt_label) => {
-                return self.lower_expr_for(e, pat, head, body, opt_label);
-            }
             ExprKind::Try(ref sub_expr) => self.lower_expr_try(e.span, sub_expr),
-            ExprKind::MacCall(_) => panic!("Shouldn't exist here"),
-        };
 
-        hir::Expr {
-            hir_id: self.lower_node_id(e.id),
-            kind,
-            span: e.span,
-            attrs: e.attrs.iter().map(|a| self.lower_attr(a)).collect::<Vec<_>>().into(),
+            ExprKind::ForLoop(..) | ExprKind::Paren(_) => {
+                span_bug!(e.span, "Should be handled by `lower_expr`")
+            }
+            ExprKind::MacCall(_) => span_bug!(e.span, "Shouldn't exist here"),
         }
     }
 

diff --git a/src/librustc_ast_lowering/pat.rs b/src/librustc_ast_lowering/pat.rs
@@ -1,5 +1,6 @@
 use super::{ImplTraitContext, LoweringContext, ParamMode};
 
+use rustc::{middle::limits::ensure_sufficient_stack, span_bug};
 use rustc_ast::ast::*;
 use rustc_ast::ptr::P;
 use rustc_hir as hir;
@@ -9,6 +10,16 @@ use rustc_span::{source_map::Spanned, Span};
 impl<'a, 'hir> LoweringContext<'a, 'hir> {
     crate fn lower_pat(&mut self, p: &Pat) -> &'hir hir::Pat<'hir> {
         let node = match p.kind {
+            // FIXME: consider not using recursion to lower this.
+            PatKind::Paren(ref inner) => return self.lower_pat(inner),
+            _ => ensure_sufficient_stack(|| self.lower_pat_kind(p)),
+        };
+
+        self.pat_with_node_id_of(p, node)
+    }
+
+    fn lower_pat_kind(&mut self, p: &Pat) -> hir::PatKind<'hir> {
+        match p.kind {
             PatKind::Wild => hir::PatKind::Wild,
             PatKind::Ident(ref binding_mode, ident, ref sub) => {
                 let lower_sub = |this: &mut Self| sub.as_ref().map(|s| this.lower_pat(&*s));
@@ -74,11 +85,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 // If we reach here the `..` pattern is not semantically allowed.
                 self.ban_illegal_rest_pat(p.span)
             }
-            PatKind::Paren(ref inner) => return self.lower_pat(inner),
-            PatKind::MacCall(_) => panic!("Shouldn't exist here"),
-        };
-
-        self.pat_with_node_id_of(p, node)
+            PatKind::Paren(_) => span_bug!(p.span, "Should be handled by `lower_pat`"),
+            PatKind::MacCall(_) => span_bug!(p.span, "Shouldn't exist here"),
+        }
     }
 
     fn lower_pat_tuple(

diff --git a/src/librustc_interface/util.rs b/src/librustc_interface/util.rs
@@ -83,14 +83,7 @@ pub fn create_session(
     (Lrc::new(sess), Lrc::new(codegen_backend), source_map)
 }
 
-// Temporarily have stack size set to 32MB to deal with various crates with long method
-// chains or deep syntax trees, except when on Haiku.
-// FIXME(oli-obk): get https://github.com/rust-lang/rust/pull/55617 the finish line
-#[cfg(not(target_os = "haiku"))]
-const STACK_SIZE: usize = 32 * 1024 * 1024;
-
-#[cfg(target_os = "haiku")]
-const STACK_SIZE: usize = 16 * 1024 * 1024;
+const STACK_SIZE: usize = 2 * 1024 * 1024;
 
 fn get_stack_size() -> Option<usize> {
     // FIXME: Hacks on hacks. If the env is trying to override the stack size

diff --git a/src/librustc_mir/monomorphize/collector.rs b/src/librustc_mir/monomorphize/collector.rs
@@ -368,7 +368,9 @@ fn collect_items_rec<'tcx>(
             recursion_depth_reset = Some(check_recursion_limit(tcx, instance, recursion_depths));
             check_type_length_limit(tcx, instance);
 
-            collect_neighbours(tcx, instance, &mut neighbors);
+            rustc::middle::limits::ensure_sufficient_stack(|| {
+                collect_neighbours(tcx, instance, &mut neighbors);
+            });
         }
         MonoItem::GlobalAsm(..) => {
             recursion_depth_reset = None;
@@ -1134,7 +1136,9 @@ fn collect_miri<'tcx>(tcx: TyCtxt<'tcx>, alloc_id: AllocId, output: &mut Vec<Mon
         Some(GlobalAlloc::Memory(alloc)) => {
             trace!("collecting {:?} with {:#?}", alloc_id, alloc);
             for &((), inner) in alloc.relocations().values() {
-                collect_miri(tcx, inner, output);
+                rustc::middle::limits::ensure_sufficient_stack(|| {
+                    collect_miri(tcx, inner, output);
+                });
             }
         }
         Some(GlobalAlloc::Function(fn_instance)) => {

diff --git a/src/librustc_mir_build/build/expr/as_temp.rs b/src/librustc_mir_build/build/expr/as_temp.rs
@@ -3,7 +3,7 @@
 use crate::build::scope::DropKind;
 use crate::build::{BlockAnd, BlockAndExtension, Builder};
 use crate::hair::*;
-use rustc::middle::region;
+use rustc::middle::{region, limits::ensure_sufficient_stack};
 use rustc::mir::*;
 use rustc_hir as hir;
 use rustc_span::symbol::sym;
@@ -22,7 +22,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         M: Mirror<'tcx, Output = Expr<'tcx>>,
     {
         let expr = self.hir.mirror(expr);
-        self.expr_as_temp(block, temp_lifetime, expr, mutability)
+        //
+        // this is the only place in mir building that we need to truly need to worry about
+        // infinite recursion. Everything else does recurse, too, but it always gets broken up
+        // at some point by inserting an intermediate temporary
+        ensure_sufficient_stack(|| self.expr_as_temp(block, temp_lifetime, expr, mutability))
     }
 
     fn expr_as_temp(

diff --git a/src/librustc_trait_selection/traits/project.rs b/src/librustc_trait_selection/traits/project.rs
@@ -17,6 +17,7 @@ use super::{VtableClosureData, VtableFnPointerData, VtableGeneratorData, VtableI
 use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use crate::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime};
 use crate::traits::error_reporting::InferCtxtExt;
+use rustc::middle::limits::ensure_sufficient_stack;
 use rustc::ty::fold::{TypeFoldable, TypeFolder};
 use rustc::ty::subst::{InternalSubsts, Subst};
 use rustc::ty::{self, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, WithConstness};
@@ -261,7 +262,7 @@ where
 {
     debug!("normalize_with_depth(depth={}, value={:?})", depth, value);
     let mut normalizer = AssocTypeNormalizer::new(selcx, param_env, cause, depth, obligations);
-    let result = normalizer.fold(value);
+    let result = ensure_sufficient_stack(|| normalizer.fold(value));
     debug!(
         "normalize_with_depth: depth={} result={:?} with {} obligations",
         depth,

diff --git a/src/librustc_trait_selection/traits/query/normalize.rs b/src/librustc_trait_selection/traits/query/normalize.rs
@@ -7,6 +7,7 @@ use crate::infer::canonical::OriginalQueryValues;
 use crate::infer::{InferCtxt, InferOk};
 use crate::traits::error_reporting::InferCtxtExt;
 use crate::traits::{Obligation, ObligationCause, PredicateObligation, Reveal};
+use rustc::middle::limits::ensure_sufficient_stack;
 use rustc::ty::fold::{TypeFoldable, TypeFolder};
 use rustc::ty::subst::Subst;
 use rustc::ty::{self, Ty, TyCtxt};
@@ -120,7 +121,7 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for QueryNormalizer<'cx, 'tcx> {
                                 ty
                             );
                         }
-                        let folded_ty = self.fold_ty(concrete_ty);
+                        let folded_ty = ensure_sufficient_stack(|| self.fold_ty(concrete_ty));
                         self.anon_depth -= 1;
                         folded_ty
                     }