codelldb with cpp can't access element in an array

[vladisaev12]

OS: Ubuntu Server 24.04
VSCode version: 1.105.1
CodeLLDB version: 1.11.8
Compiler: clang++-18/lld++-18
Debuggee: Elf64/x86_64-linux-gnu exec

Reproduction steps:

1. Make a simple cpp program that makes a std::array.
2. Add a breakpoint anywhere after the initialization of the array.
3. Add any element of the array to the watch list.

Expected:
Shows the value of the element.
Actually:
Errors out with a IndexError.

Details

Is a crash, but the crash seems intentional. Logs:

LLDB.log

[vadimcn]

Do you mean code like this?

std::array<unsigned char, 100> a = { 1, 2, 3, 4, 5};

This works fine for me. But in any case, CodeLLDB relies on the underlying LLDB engine to read variable values. The exception basically indicates that LLDB could not access that element for some reason. Are you compiling with optimizations?
Try frame variable a._M_elems[0] command, does it fail as well?

[vladisaev12]

Do you mean code like this?

std::array<unsigned char, 100> a = { 1, 2, 3, 4, 5};

Yes, but I'm pretty sure any array should work.

This works fine for me. But in any case, CodeLLDB relies on the underlying LLDB engine to read variable values. The exception basically indicates that LLDB could not access that element for some reason. Are you compiling with optimizations?

No, I do not have any optimization flags set.

I should have mentioned that I'm using ubuntu repo's lldb-server exec/lib, since my pc is too old for the lldb-server packaged with codelldb.

Try frame variable a._M_elems[0] command, does it fail as well?

Is there any difference between frame variable a._M_elems[0] and just a._M_elems[0]?

[vadimcn]

Is there any difference between frame variable a._M_elems[0] and just a._M_elems[0]?

The former is a LLDB command you enter in the Debug Console (same as one would use in CLI lldb). See this, though, and make sure you are executing a command, not evaluating an expression.
The latter is an expression evaluated by CodeLLDB on VSCode request. In the end, it ends up on the same codepath within LLDB as frame variable, but there are extra things that happen before that; so I asked you to try the command to narrow down the root cause.

I should have mentioned that I'm using ubuntu repo's lldb-server exec/lib, since my pc is too old for the lldb-server packaged with codelldb.

Usually lldb is backwards compatible with older lldb-servers, but who knows... You might want to try the same frame variable ... in the CLI lldb to see if it has the same problem.

[vladisaev12]

I should have mentioned that I'm using ubuntu repo's lldb-server exec/lib, since my pc is too old for the lldb-server packaged with codelldb.

Usually lldb is backwards compatible with older lldb-servers, but who knows... You might want to try the same frame variable ... in the CLI lldb to see if it has the same problem.

lldb-server-18.so.1 has some features that my cpu is missing and causes codelldb to crash.
I'm using a custom lldb-server, because of subversion specifics. This is its own issue where you use a specific version of lldb instead of a more general one, aka lldb-server-18 instead of lldb-server-18.1.3.