[lldb] [test] Improve comment on expr-after-step-after-crash tests

[mgorny]

Summary

Make the comment indicate more strongly that this behavior
is Darwin-specific and it is not a bug for other platforms to behave
differently.

[emaste]

How does Windows fit into this? Other than that Q, LGTM.

[mgorny]

In D90876#2377541, @emaste wrote:

How does Windows fit into this? Other than that Q, LGTM.

@labath, any clue?

[labath]

In D90876#2377544, @mgorny wrote:

In D90876#2377541, @emaste wrote:

How does Windows fit into this? Other than that Q, LGTM.

@labath, any clue?

I don't know... Since the test is not annotated, I guess it somehow makes this work, but I haven't been able to find the code that makes it happen.

The problem with this test is that the behavior it prescribes is not compatible with applications that handle SIGSEGV themselves. People have complained about that, including on macos (see D89315). If we were able to tell that the application will not actually handle the SEGV (or other signal), then displaying the process as "crashed" would actually be a good signal to the user. But I don't know of a reasonable way to check whether injecting a signal will cause the app to exit. The situation is probably the same on windows, as it also allows apps to handle their own exceptions (unless we're actually checking whether the application will handle it, which I doubt) , but noone probably noticed it yet...

[mgorny]

@zturner, could you tell us what is the expected behavior on Windows? Is it the same as Darwin (i.e. as expected by this test), or do you consider it incidental and would prefer skipping the test on Windows too?

[labath]

Zach is pretty much inactive. @amccarth is a better windows contact these days.

[labath]

Getting this off my queue. I think the change is fine, but I can also live with the original comment.

[emaste]

Fine with me, or maybe "A test for Darwin- (and prehaps Windows-)specific behavior."

[emaste]

ping

lldb/test/API/functionalities/inferior-crashing/TestInferiorCrashingStep.py

class CrashingInferiorStepTestCase(TestBase):
 
     @skipIfTargetAndroid()  # debuggerd interferes with this test on Android
     @expectedFailureAll(oslist=["windows"], bugnumber="llvm.org/pr24778")
     def test_inferior_crashing_step_after_break(self):
         """Test that lldb functions correctly after stepping through a crash."""
         self.build()
         self.inferior_crashing_step_after_break()
 
-    # Inferior exits after stepping after a segfault. This is working as
-    # intended IMHO.
+    # A test for Darwin-specific behavior.  On other platforms, inferior
+    # exits after stepping after a segfault.
     @skipIf(oslist=["freebsd", "linux", "netbsd"])
     def test_inferior_crashing_expr_step_and_expr(self):
         """Test that lldb expressions work before and after stepping after a crash."""
         self.build()
         self.inferior_crashing_expr_step_expr()
 
     def set_breakpoint(self, line):
         lldbutil.run_break_set_by_file_and_line(

lldb/test/API/functionalities/inferior-crashing/recursive-inferior/TestRecursiveInferiorStep.py

class CrashingRecursiveInferiorStepTestCase(TestBase):
 
     @skipIfTargetAndroid()  # debuggerd interferes with this test on Android
     @expectedFailureAll(oslist=["windows"], bugnumber="llvm.org/pr24778")
     def test_recursive_inferior_crashing_step_after_break(self):
         """Test that lldb functions correctly after stepping through a crash."""
         self.build()
         self.recursive_inferior_crashing_step_after_break()
 
-    # Inferior exits after stepping after a segfault. This is working as
-    # intended IMHO.
+    # A test for Darwin-specific behavior.  On other platforms, inferior
+    # exits after stepping after a segfault.
     @skipIf(oslist=["freebsd", "linux", "netbsd"])
     def test_recursive_inferior_crashing_expr_step_and_expr(self):
         """Test that lldb expressions work before and after stepping after a crash."""
         self.build()
         self.recursive_inferior_crashing_expr_step_expr()
 
     def set_breakpoint(self, line):
         lldbutil.run_break_set_by_file_and_line(