Clear and restore errinfo on entry to and normal return from C.

Author: aardvark179

CHANGELOG.md

@@ -10,6 +10,7 @@ Bug fixes:
 * Show the interleaved host and guest stacktrace for host exceptions (#2226).
 * Fix the label of the first location reported by `Thread#backtrace_locations` (#2229).
 * Fix `Thread.handle_interrupt` to defer non-pure interrupts until the end of the `handle_interrupt` block (#2219).
+* Clear and restore errinfo on entry and normal return from methods in C extensions (#2227).
 
 Compatibility:
 

lib/truffle/truffle/cext_ruby.rb

@@ -31,12 +31,16 @@ def rb_define_method(mod, name, function, argc)
         args = [Primitive.cext_wrap(self), *args.map! { |arg| Primitive.cext_wrap(arg) }]
       end
 
+      exc = $!
+      Truffle::Type.set_last_exception(nil)
       # Using raw execute instead of #call here to avoid argument conversion
 
       # We must set block argument if given here so that the
       # `rb_block_*` functions will be able to find it by walking the
       # stack.
-      Primitive.cext_unwrap(Primitive.call_with_c_mutex_and_frame(function, args, block))
+      res = Primitive.cext_unwrap(Primitive.call_with_c_mutex_and_frame(function, args, block))
+      Truffle::Type.set_last_exception(exc)
+      res
     end
 
     mod.define_method(name, method_body)

spec/ruby/optional/capi/exception_spec.rb

@@ -38,6 +38,26 @@
     end
   end
 
+  describe "rb_errinfo" do
+    it "is cleared when entering a C method" do
+      begin
+        raise StandardError
+      rescue
+        $!.class.should == StandardError
+        @s.rb_errinfo().should == nil
+      end
+    end
+
+    it "does not clear $! in the calling method" do
+      begin
+        raise StandardError
+      rescue
+        @s.rb_errinfo()
+        $!.class.should == StandardError
+      end
+    end
+  end
+
   describe "rb_set_errinfo" do
     after :each do
       @s.rb_set_errinfo(nil)

spec/ruby/optional/capi/ext/exception_spec.c

@@ -8,6 +8,10 @@
 extern "C" {
 #endif
 
+VALUE exception_spec_rb_errinfo(VALUE self) {
+  return rb_errinfo();
+}
+
 VALUE exception_spec_rb_exc_new(VALUE self, VALUE str) {
   char *cstr = StringValuePtr(str);
   return rb_exc_new(rb_eException, cstr, strlen(cstr));
@@ -41,6 +45,7 @@ VALUE exception_spec_rb_make_exception(VALUE self, VALUE ary) {
 
 void Init_exception_spec(void) {
   VALUE cls = rb_define_class("CApiExceptionSpecs", rb_cObject);
+  rb_define_method(cls, "rb_errinfo", exception_spec_rb_errinfo, 0);
   rb_define_method(cls, "rb_exc_new", exception_spec_rb_exc_new, 1);
   rb_define_method(cls, "rb_exc_new2", exception_spec_rb_exc_new2, 1);
   rb_define_method(cls, "rb_exc_new3", exception_spec_rb_exc_new3, 1);