Push a real iseq in rb_vm_push_frame_fname()

Previously, vm_make_env_each() (used during proc
creation and for the debug inspector C API) picked up the
non-GC-allocated iseq that rb_vm_push_frame_fname() creates,
which led to a SEGV when the GC tried to mark the non GC object.

Put a real iseq imemo instead. Speed should be about the same since
the old code also did a imemo allocation and a malloc allocation.

Real iseq allows ironing out the special-casing of dummy frames in
rb_execution_context_mark() and rb_execution_context_update(). A check
is added to RubyVM::ISeq#eval, though, to stop attempts to run dummy
iseqs.

[Bug #21180]

Co-authored-by: Aaron Patterson <tenderlove@ruby-lang.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/test/fiber/test_scheduler.rb b/test/fiber/test_scheduler.rb
index 62424fc489..81d4581bea 100644
--- a/test/fiber/test_scheduler.rb
+++ b/test/fiber/test_scheduler.rb
@@ -139,6 +139,19 @@ class TestFiberScheduler < Test::Unit::TestCase
     end
   end
 
+  def test_iseq_compile_under_gc_stress_bug_21180
+    Thread.new do
+      scheduler = Scheduler.new
+      Fiber.set_scheduler scheduler
+
+      Fiber.schedule do
+        EnvUtil.under_gc_stress do
+          RubyVM::InstructionSequence.compile_file(File::NULL)
+        end
+      end
+    end.join
+  end
+
   def test_deadlock
     mutex = Thread::Mutex.new
     condition = Thread::ConditionVariable.new