Populate rb_errinfo when rb_protect captures a ruby exception.

(cherry picked from commit 6a1aaa7)

Author: aardvark179

lib/truffle/truffle/cext.rb

@@ -992,6 +992,7 @@ def rb_protect(function, arg, write_status, status)
     unless Primitive.object_equal(nil, e)
       store = (Thread.current[:__stored_exceptions__] ||= [])
       pos = store.push(e).size
+      Primitive.thread_set_exception(extract_ruby_exception(e))
     end
 
     Truffle::Interop.execute_without_conversion(write_status, status, pos)

src/main/java/org/truffleruby/cext/CExtNodes.java

@@ -1185,6 +1185,23 @@ protected Object executeWithProtect(RubyProc block,
         }
     }
 
+    @CoreMethod(names = "extract_ruby_exception", onSingleton = true, required = 1)
+    public abstract static class ExtractRubyException extends CoreMethodArrayArgumentsNode {
+
+        /** Profiled version of {@link ExceptionOperations#rethrow(Throwable)} */
+        @Specialization
+        protected Object executeThrow(CapturedException captured,
+                @Cached ConditionProfile rubyExceptionProfile,
+                @Cached ConditionProfile errorProfile) {
+            final Throwable e = captured.getException();
+            if (rubyExceptionProfile.profile(e instanceof RaiseException)) {
+                return ((RaiseException) e).getException();
+            } else {
+                return nil;
+            }
+        }
+    }
+
     @CoreMethod(names = "raise_exception", onSingleton = true, required = 1)
     public abstract static class RaiseExceptionNode extends CoreMethodArrayArgumentsNode {