[Lldb-commits] [PATCH] D76814: Preserve ThreadPlanStacks for unreported threads

Fri Mar 27 02:38:11 PDT 2020

labath added inline comments.

================
Comment at: lldb/source/Target/TargetProperties.td:183
     Desc<"A path to a python OS plug-in module file that contains a OperatingSystemPlugIn class.">;
+  def PluginReportsAllThreads: Property<"plugin-reports-all-threads", "Boolean">,
+    Global,
----------------
jingham wrote:
> labath wrote:
> > If this is relevant only for os plugins, then it would be good to reflect that in the name as well.
> I thought about that.  In the future a regular Process plugin might decide it was too expensive to report all threads as well.  There's nothing in this patch that wouldn't "just work" with that case as well.  Leaving the OS out was meant to indicate this was about how the Process plugin OR any of its helpers (e.g. the OS Plugin) produces threads.
Well, I am hoping that if we ever extend this support to the regular process plugins, we will implement it in a way where the plugin itself can tell us whether it is operating/supporting this mode (which I guess would involve a new gdb-remote packet and some specification of what exactly should happen when it gets sent), instead of relying on the user to set this correctly.

I mean, in an ideal world this is I would want to happen with the python plugins as well, but it seems that we are stuck with some existing plugins which already do that. However, I wouldn't want to plan on the same thing happening again. :)

================
Comment at: lldb/test/API/functionalities/thread_plan/TestThreadPlanCommands.py:23
+
+    def check_list_output(self, command, active_plans = [], completed_plans = [], discarded_plans = []):
+        # Check the "thread plan list" output against a list of active & completed and discarded plans.
----------------
jingham wrote:
> labath wrote:
> > this looks like a model example for using `self.filecheck`
> I don't see that.  Do you mean write a file check matching file with the contents of the three arrays in this function, and then run file check on that?  Or did you mean convert the call sites into embedded patterns and then call file check on myself?  But then I'd have to also embed the headers in the body such that they came in the right order for all the tests.  Neither of these seem like attractive options to me.  It doesn't seem like it will be hard to maintain this little checker, and I don't see what I would gain by using file check instead.
What I meant was doing doing something like:
```
self.filecheck("thread plan list %d"%(current_id), __file__, "--check-prefix=CHECK1")
# CHECK1:      Active plan stack:
# CHECK1-NEXT: Element 0: Base thread plan
# CHECK1-NEXT: Element 1: Stepping over line main.c
# CHECK1-EMPTY:
```
instead of `self.check_list_output(..., [], ["Stepping over line main.c"])`

The main advantage of that I see is in the error messages it produces. If anything goes wrong, the most likely error message we're going to get is "9 != 10, Too many elements in match arrays".  The second most likely error message is "False is not True, Didn't find active plan Stepping over line main.c". If the same happens while using filecheck, it would print the string it is trying to match, the line it is trying to match it against, and the line of a "possible intended match", which makes it much easier to figure out what is going on without debugging the test. Now you could embed all of that into this matcher function, but then you're sort of reinventing FileCheck.

The second advantage is that it is easier to see what is the "expected" output supposed to be when it is layout out like this, instead of embedded in the logic of the matcher. That may introduce some amount of repetition for specifying the common parts of the output, but that is not necessarily bad (because it's more readable). If there is a huge amount of repetition, then there are ways to avoid that via using multiple prefixes:
```
FileCheck --check-prefixes=ALL,FIRST
...
FileCheck --check-prefixes=ALL,SECOND
# ALL: Active plan stack:
# ALL: Element 0: Base thread plan
# FIRST: Element 1: Stepping over line main.c
# SECOND: Element 1: ???
```
But that again makes it harder to see the expected output, so it should be balanced against that.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D76814/new/

https://reviews.llvm.org/D76814