Raise ArgumentError when ddog_prof_Profile_add returns a failure

This will allow us to have early warning for when we're using the
API incorrectly.

See also DataDog/libdatadog#87 .

ext/ddtrace_profiling_native_extension/stack_recorder.c

@@ -317,9 +317,11 @@ void record_sample(VALUE recorder_instance, ddog_prof_Sample sample) {
 
   struct active_slot_pair active_slot = sampler_lock_active_profile(state);
 
-  ddog_prof_Profile_add(active_slot.profile, sample);
+  uint64_t success = ddog_prof_Profile_add(active_slot.profile, sample);
 
   sampler_unlock_active_profile(active_slot);
+
+  if (!success) rb_raise(rb_eArgError, "Failed to record sample: ddog_prof_Profile_add returned failure status code");
 }
 
 void record_endpoint(VALUE recorder_instance, uint64_t local_root_span_id, ddog_CharSlice endpoint) {

spec/datadog/profiling/stack_recorder_spec.rb

@@ -176,6 +176,21 @@ def sample_types_from(decoded_profile)
       end
     end
 
+    context 'when sample is invalid' do
+      context 'because the local root span id is being defined using a string instead of as a number' do
+        let(:metric_values) { { 'cpu-time' => 123, 'cpu-samples' => 456, 'wall-time' => 789 } }
+
+        it do
+          # We're using `_native_sample` here to test the behavior of `record_sample` in `stack_recorder.c`
+          expect do
+            Datadog::Profiling::Collectors::Stack::Testing._native_sample(
+              Thread.current, stack_recorder, metric_values, { 'local root span id' => 'incorrect' }.to_a, [], 400, false
+            )
+          end.to raise_error(ArgumentError)
+        end
+      end
+    end
+
     describe 'trace endpoint behavior' do
       let(:metric_values) { { 'cpu-time' => 101, 'cpu-samples' => 1, 'wall-time' => 789 } }
       let(:samples) { samples_from_pprof(encoded_pprof) }