[lldb] Print the backtrace for all threads if the test breakpoint can't be hit

[teemperor]

Summary

At the moment if a test fails to hits the breakpoint we set in run_to_source_breakpoint
the test suite just prints:

AssertionError: 0 != 1 : Expected 1 thread to stop at breakpoint, 0 did

Often these errors happen because the debuggee crashed before that breakpoint is being
hit or the process failed to launch but it's hard to tell what happened from the current error.

This patch adds that we now print the backtrace of all threads in case the test failed
because we didn't hit the right breakpoint

[mib]

LGTM!

[augusto2112]

LGTM

[JDevlieghere]

LGTM. Are there other places where we check this, either in lldbutil or maybe more generally a pattern in the tests that could be extracted into a helper?

[teemperor]

In D103439#2791298, @JDevlieghere wrote:

LGTM. Are there other places where we check this, either in lldbutil or maybe more generally a pattern in the tests that could be extracted into a helper?

From what I can see all our lldbutil functions that run to a breakpoint end up calling this function so this should cover everything beside the tests that manually do stuff like "continue" and so on. But there might be some utility function for going to the next breakpoint that are missing this. I'll check, thanks!

[jingham]

In D103439#2791324, @teemperor wrote:

In D103439#2791298, @JDevlieghere wrote:

LGTM. Are there other places where we check this, either in lldbutil or maybe more generally a pattern in the tests that could be extracted into a helper?

From what I can see all our lldbutil functions that run to a breakpoint end up calling this function so this should cover everything beside the tests that manually do stuff like "continue" and so on. But there might be some utility function for going to the next breakpoint that are missing this. I'll check, thanks!

You probably also want to do this to "lldbutil.continue_to_breakpoint", except that doesn't actually do any tests. It should really be rewritten to take a TestBase and do the assert's in the function, it is inconvenient to use as currently written.

lldb/packages/Python/lldbsuite/test/lldbutil.py

def get_crashed_threads(test, process):
     threads = []
     if process.GetState() != lldb.eStateStopped:
         return threads
     for thread in process:
         if is_thread_crashed(test, thread):
             threads.append(thread)
     return threads
 
+def get_thread_overview(test):
+    """Returns a string providing an overview over all current threads.
+    Should be used for making test errors more expressive."""
+    test.runCmd("thread backtrace all")
+    return "Current threads:\n" + test.res.GetOutput()
+
 # Helper functions for run_to_{source,name}_breakpoint:
 
 def run_to_breakpoint_make_target(test, exe_name = "a.out", in_cwd = True):
     if in_cwd:
         exe = test.getBuildArtifact(exe_name)
 
     # Create the target
     target = test.dbg.CreateTarget(exe)
def run_to_breakpoint_do_run(test, target, bkpt, launch_info = None,
     test.assertEqual(process.GetState(), lldb.eStateStopped)
 
     # Frame #0 should be at our breakpoint.
     threads = get_threads_stopped_at_breakpoint(
                 process, bkpt)
 
     num_threads = len(threads)
     if only_one_thread:
-        test.assertEqual(num_threads, 1, "Expected 1 thread to stop at breakpoint, %d did."%(num_threads))
-    else:
-        test.assertGreater(num_threads, 0, "No threads stopped at breakpoint")
+        test.assertEqual(num_threads, 1,
+                         "Expected 1 thread to stop at breakpoint, %d did.\n%s"
+                         % (num_threads, get_thread_overview(test)))
+    else:
+        test.assertGreater(num_threads, 0,
+                           "No threads stopped at breakpoint.\n%s" %
+                           (get_thread_overview(test)))
 
     thread = threads[0]
     return (target, process, thread, bkpt)
 
 def run_to_name_breakpoint (test, bkpt_name, launch_info = None,
                             exe_name = "a.out",
                             bkpt_module = None,
                             in_cwd = True,