Avoid underflow of rb_yjit_live_iseq_count

This value is only incremented when rb_iseq_translate_threaded_code is
called, which doesn't happen for iseqs which result in a syntax error.

This is easy to hit by running a debug build with RUBY_FREE_AT_EXIT=1,
but any build and options could underflow this value by running enough
evals.

1 files changed, 10 insertions, 0 deletions

diff --git a/bootstraptest/test_eval.rb b/bootstraptest/test_eval.rb
index a9f389c673..47e2924846 100644
--- a/bootstraptest/test_eval.rb
+++ b/bootstraptest/test_eval.rb
@@ -227,6 +227,16 @@ assert_equal %q{[10, main]}, %q{
   }, '[ruby-dev:31372]'
 end
 
+assert_normal_exit %{
+  $stderr = STDOUT
+  5000.times do
+    begin
+      eval "0 rescue break"
+    rescue SyntaxError
+    end
+  end
+}
+
 assert_normal_exit %q{
   $stderr = STDOUT
   class Foo