Commits on Feb 2, 2023

1. Fix profiler sometimes not adding the "In native code" placeholder …

   **What does this PR do?**:
   
   In #2583 we added a very small check to our custom
   `ddtrace_rb_profile_frames` to match a similar fix added to upstream
   Ruby.
   
   But I've just spotted this caused one of the profiling tests to become
   flaky:
   
   ```
   $ bundle exec rspec spec/datadog/profiling --seed 14514
   
   Failures:
   
     1) Datadog::Profiling::Collectors::Stack when sampling a thread with empty locations gathers a one-element stack with a "In native code" placeholder
        Failure/Error: expect(gathered_stack).to contain_exactly({ base_label: '', path: 'In native code', lineno: 0 })
   
          expected collection contained:  [{:base_label=>"", :lineno=>0, :path=>"In native code"}]
          actual collection contained:    []
          the missing elements were:      [{:base_label=>"", :lineno=>0, :path=>"In native code"}]
        # ./spec/datadog/profiling/collectors/stack_spec.rb:373:in `block (3 levels) in <top (required)>'
        # ./spec/spec_helper.rb:220:in `block (2 levels) in <top (required)>'
        # ./spec/spec_helper.rb:112:in `block (2 levels) in <top (required)>'
        # /home/ivo.anjo/.rvm/gems/ruby-2.7.7/gems/webmock-3.13.0/lib/webmock/rspec.rb:37:in `block (2 levels) in <top (required)>'
   
     2) Datadog::Profiling::Collectors::Stack when sampling a thread with empty locations when marking sample as being in garbage collection gathers a two-element stack with a placeholder for "In native code" and another for garbage collection
        Failure/Error:
          expect(gathered_stack).to contain_exactly(
            { base_label: '', path: 'Garbage Collection', lineno: 0 },
            { base_label: '', path: 'In native code', lineno: 0 }
          )
   
          expected collection contained:  [{:base_label=>"", :lineno=>0, :path=>"Garbage Collection"}, {:base_label=>"", :lineno=>0, :path=>"In native code"}]
          actual collection contained:    [{:base_label=>"", :lineno=>0, :path=>"Garbage Collection"}]
          the missing elements were:      [{:base_label=>"", :lineno=>0, :path=>"In native code"}]
        # ./spec/datadog/profiling/collectors/stack_spec.rb:380:in `block (4 levels) in <top (required)>'
        # ./spec/spec_helper.rb:220:in `block (2 levels) in <top (required)>'
        # ./spec/spec_helper.rb:112:in `block (2 levels) in <top (required)>'
        # /home/ivo.anjo/.rvm/gems/ruby-2.7.7/gems/webmock-3.13.0/lib/webmock/rspec.rb:37:in `block (2 levels) in <top (required)>'
   
   Finished in 13.42 seconds (files took 0.44192 seconds to load)
   563 examples, 2 failures, 15 pending
   
   Failed examples:
   
   rspec ./spec/datadog/profiling/collectors/stack_spec.rb:372 # Datadog::Profiling::Collectors::Stack when sampling a thread with empty locations gathers a one-element stack with a "In native code" placeholder
   rspec ./spec/datadog/profiling/collectors/stack_spec.rb:379 # Datadog::Profiling::Collectors::Stack when sampling a thread with empty locations when marking sample as being in garbage collection gathers a two-element stack with a placeholder for "In native code" and another for garbage collection
   ```
   
   This issue was caused by the `cfp == NULL` check being added before the
   `end_cfp == NULL` check we have to detect when we should add the "In
   native code" placeholder.
   
   In some cases, `cfp` is set and the placeholder is added, but in others,
   it's not.
   
   To fix this, I've swapped the order of the checks, so that the check to
   introduce the placeholder gets higher priority.
   
   **Motivation**:
   
   Fix bug (that also causes flaky tests).
   
   **Additional Notes**:
   
   (N/A)
   
   **How to test the change?**:
   
   Validate that running profiling test suite works with for instance
   seed 14154.

   

   ivoanjo committed Feb 2, 2023
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