fixup! Add comments to the test

Author: igorkudrin

lldb/test/API/functionalities/thread/finish-from-empty-func/TestEmptyFuncThreadStepOut.py

@@ -13,12 +13,15 @@ class FinishFromEmptyFunctionTestCase(TestBase):
 
     @skipIf(compiler="clang", compiler_version=['<', '17.0'])
     def test_finish_from_empty_function(self):
-        """Test that when stopped at a breakpoint in an empty function, finish leaves it correctly."""
+        """Test that when stopped at a breakpoint located at the last instruction
+        of a function, finish leaves it correctly."""
         self.build()
         target, _, thread, _ = lldbutil.run_to_source_breakpoint(
             self, "// Set breakpoint here", lldb.SBFileSpec("main.c")
         )
-        # Find the last instruction address of 'done()' and set a breakpoint there.
+        # Find the address of the last instruction of 'done()' and set a breakpoint there.
+        # Even though 'done()' is empty, it may contain prologue and epilogue code, so
+        # simply setting a breakpoint at the function can place it before 'ret'.
         error = lldb.SBError()
         ret_bp_addr = lldb.SBAddress()
         while True:
@@ -28,9 +31,12 @@ def test_finish_from_empty_function(self):
             if "done" in frame.GetFunctionName():
                 ret_bp_addr = frame.GetPCAddress()
             elif ret_bp_addr.IsValid():
+                # The entire function 'done()' has been stepped through, so 'ret_bp_addr'
+                # now contains the address of its last instruction, i.e. 'ret'.
                 break
         ret_bp = target.BreakpointCreateByAddress(ret_bp_addr.GetLoadAddress(target))
         self.assertTrue(ret_bp.IsValid())
+        # Resume the execution and hit the new breakpoint.
         self.runCmd("cont")
         if self.TraceOn():
             self.runCmd("bt")