[gcc/devel/rust/master] Add a recursion-limit when resolving Parameter Types

[Thomas Schwinge <tschwinge@gcc.gnu.org>]

https://gcc.gnu.org/g:c6dc53f9e2e95295936c970019c8cbd573a8e4f6

commit c6dc53f9e2e95295936c970019c8cbd573a8e4f6
Author: Philip Herron <philip.herron@embecosm.com>
Date:   Wed Nov 3 14:37:52 2021 +0000

    Add a recursion-limit when resolving Parameter Types
    
    This limit is likely way too low but its ok for now to get decent
    backtraces for the test-cases we are working with right now.

Diff:
---
 gcc/rust/backend/rust-compile-context.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/gcc/rust/backend/rust-compile-context.h b/gcc/rust/backend/rust-compile-context.h
index 551e0413007..396cb10c263 100644
--- a/gcc/rust/backend/rust-compile-context.h
+++ b/gcc/rust/backend/rust-compile-context.h
@@ -367,6 +367,9 @@ public:
 
   void visit (const TyTy::ParamType &param) override
   {
+    recursion_count++;
+    rust_assert (recursion_count < kDefaultRecusionLimit);
+
     param.resolve ()->accept_vis (*this);
   }
 
@@ -670,12 +673,16 @@ public:
 
 private:
   TyTyResolveCompile (Context *ctx, bool trait_object_mode)
-    : ctx (ctx), trait_object_mode (trait_object_mode), translated (nullptr)
+    : ctx (ctx), trait_object_mode (trait_object_mode), translated (nullptr),
+      recursion_count (0)
   {}
 
   Context *ctx;
   bool trait_object_mode;
   ::Btype *translated;
+  size_t recursion_count;
+
+  static const size_t kDefaultRecusionLimit = 5;
 };
 
 } // namespace Compile