unsafe: Handle multi unsafe contexts by using stack

Co-authored-by: philberty <philip.herron@embecosm.com>

3 files changed, 60 insertions, 7 deletions

diff --git a/gcc/rust/checks/errors/rust-unsafe-checker.cc b/gcc/rust/checks/errors/rust-unsafe-checker.cc
index d79254c..def3cc1 100644
--- a/gcc/rust/checks/errors/rust-unsafe-checker.cc
+++ b/gcc/rust/checks/errors/rust-unsafe-checker.cc
@@ -36,6 +36,29 @@ UnsafeChecker::go (HIR::Crate &crate)
 }
 
 void
+UnsafeChecker::push_unsafe (HirId id)
+{
+  unsafe_contexts.emplace_back (id);
+}
+
+HirId
+UnsafeChecker::pop_unsafe ()
+{
+  rust_assert (!unsafe_contexts.empty ());
+
+  auto last = unsafe_contexts.back ();
+  unsafe_contexts.pop_back ();
+
+  return last;
+}
+
+bool
+UnsafeChecker::is_unsafe_context ()
+{
+  return !unsafe_contexts.empty ();
+}
+
+void
 UnsafeChecker::visit (IdentifierExpr &ident_expr)
 {}
 
@@ -94,7 +117,7 @@ UnsafeChecker::visit (DereferenceExpr &expr)
   rust_assert (context.lookup_type (to_deref, &to_deref_type));
 
   if (to_deref_type->get_kind () == TyTy::TypeKind::POINTER
-      && !in_unsafe_context)
+      && !is_unsafe_context ())
     rust_error_at (expr.get_locus (), "dereference of raw pointer requires "
 				      "unsafe function or block");
 }
@@ -320,11 +343,11 @@ UnsafeChecker::visit (ReturnExpr &expr)
 void
 UnsafeChecker::visit (UnsafeBlockExpr &expr)
 {
-  in_unsafe_context = true;
+  push_unsafe (expr.get_mappings ().get_hirid ());
 
   expr.get_block_expr ()->accept_vis (*this);
 
-  in_unsafe_context = false;
+  pop_unsafe ();
 }
 
 void
@@ -485,11 +508,15 @@ UnsafeChecker::visit (UseDeclaration &use_decl)
 void
 UnsafeChecker::visit (Function &function)
 {
-  in_unsafe_context = function.get_qualifiers ().is_unsafe ();
+  auto is_unsafe_fn = function.get_qualifiers ().is_unsafe ();
+
+  if (is_unsafe_fn)
+    push_unsafe (function.get_mappings ().get_hirid ());
 
   function.get_definition ()->accept_vis (*this);
 
-  in_unsafe_context = false;
+  if (is_unsafe_fn)
+    pop_unsafe ();
 }
 
 void
diff --git a/gcc/rust/checks/errors/rust-unsafe-checker.h b/gcc/rust/checks/errors/rust-unsafe-checker.h
index de122cb..3c81707 100644
--- a/gcc/rust/checks/errors/rust-unsafe-checker.h
+++ b/gcc/rust/checks/errors/rust-unsafe-checker.h
@@ -32,8 +32,24 @@ public:
   void go (HIR::Crate &crate);
 
 private:
-  /* Are we currently in an unsafe function or block ? */
-  bool in_unsafe_context;
+  /* Stack of unsafe contexts */
+  std::vector<HirId> unsafe_contexts;
+
+  /**
+   * Add an unsafe context to the stack. To call when entering unsafe blocks
+   */
+  void push_unsafe (HirId id);
+
+  /**
+   * Remove an unsafe context from the stack. Call this when exiting unsafe
+   * blocks
+   */
+  HirId pop_unsafe ();
+
+  /**
+   * Are we currently in an unsafe context or not
+   */
+  bool is_unsafe_context ();
 
   Resolver::TypeCheckContext &context;
 
@@ -170,6 +186,7 @@ private:
   virtual void visit (InferredType &type) override;
   virtual void visit (BareFunctionType &type) override;
 };
+
 } // namespace HIR
 } // namespace Rust
 
diff --git a/gcc/testsuite/rust/compile/unsafe4.rs b/gcc/testsuite/rust/compile/unsafe4.rs
index 06cdb4a..7d1356b 100644
--- a/gcc/testsuite/rust/compile/unsafe4.rs
+++ b/gcc/testsuite/rust/compile/unsafe4.rs
@@ -18,3 +18,12 @@ fn baz() -> i32 {
 
     *p_a // { dg-error "dereference of raw pointer" }
 }
+
+unsafe fn qux() -> i32 {
+    let a = 15;
+    let p_a = &a as *const i32;
+
+    unsafe {}
+
+    *p_a
+}