> On Jan 14, 2022, at 10:13 AM, fhjiwerfghr fhiewrgfheir via lldb-dev
> <lldb-dev@lists.llvm.org> wrote:
>
> I'm sorry in advance, if it's not a correct mailing list, there doesn't seem
> to be lldb-usage mailing list.
>
> I'm writing a pretty-printer python script, which - to cut to the chase,
> pretty prints members of a class by using EvaluateExpression and creating new
> object inside it. It doesn't seem to work - i'm getting "<could not resolve
> type>" error. Should my idea work in a first place and i't s a bug or it
> shouldn't and i need to find a different solution?
This might be a case where -flimit-debug-info, the default setting for things
on linux, is getting in the way. Can you try specifying -glldb on the command
line and see if that fixes things? The default case for linux is for the
compiler to not emit debug info for types that might exist in other frameworks.
This was an effort to reduce .o file sizes. In this case, you might be running
into a case where the debug info for std::string_view is being emitted as a
forward declarartion, so the expression parser can't end up using it. The best
way to tell is to make a local "std::string_view" object that has valid
contents and see if you can expand the variable in the debugger. I am not a fan
of this approach of omitting debug info that the debugger needs, but it is
unfortunately the default setting for linux compiles.
The other thing to mention is it is a really bad idea to run expressions as
part of data formatters or summary providers. Why? Expressions can end up
resuming all threads if the expression deadlocks for any reason or if the
expression doesn't complete. Of course if you have properties that are
generated, you don't have much of a choice, so try to only use expressions if
you know the expression won't ever deadlock due to another thread holding a
mutex or other locking mechanism. If you can, best to try and just access
existing data within an object if at all possible.
>
> I'm attaching a repro case:
>
> clang++ q.cpp -g -o o -std=c++20
> lldb o
> command script import lldb_script.py
> br set --file q.cpp --line 19
> r
> print c
>
>
> it prints:
> (lldb) print c
> (C) $0 = CCC {
> = <could not resolve type>
> }
>
> it should something akin to:
> (lldb) print c
> (C) $0 = CCC {
> b = B {
> a = A {
> id = "qwerty"
> }
> }
> }
>
>
>
> <q.cpp><lldb_script.py>_______________________________________________
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