rust-lldb: cannot get backtrace on macOS

[alexreg]

I have a breakpoint set on rust_panic, but when I hit this and then do bt, I get:

error: need to add support for DW_TAG_base_type '()' encoded with DW_ATE = 0x7, bit_size = 0
Traceback (most recent call last):
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 89, in print_val
    is_tuple_like = False)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 210, in print_struct_val
    body = separator.join([render_child(idx) for idx in range(field_start_index, len(fields))])
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 203, in render_child
    return this + print_val(field_val.get_wrapped_value(), internal_dict)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 89, in print_val
    is_tuple_like = False)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 210, in print_struct_val
    body = separator.join([render_child(idx) for idx in range(field_start_index, len(fields))])
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 203, in render_child
    return this + print_val(field_val.get_wrapped_value(), internal_dict)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 89, in print_val
    is_tuple_like = False)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 210, in print_struct_val
    body = separator.join([render_child(idx) for idx in range(field_start_index, len(fields))])
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 203, in render_child
    return this + print_val(field_val.get_wrapped_value(), internal_dict)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 89, in print_val
    is_tuple_like = False)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 210, in print_struct_val
    body = separator.join([render_child(idx) for idx in range(field_start_index, len(fields))])
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 203, in render_child
    return this + print_val(field_val.get_wrapped_value(), internal_dict)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 89, in print_val
    is_tuple_like = False)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 210, in print_struct_val
    body = separator.join([render_child(idx) for idx in range(field_start_index, len(fields))])
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 203, in render_child
    return this + print_val(field_val.get_wrapped_value(), internal_dict)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 89, in print_val
    is_tuple_like = False)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 210, in print_struct_val
    body = separator.join([render_child(idx) for idx in range(field_start_index, len(fields))])
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 203, in render_child
    return this + print_val(field_val.get_wrapped_value(), internal_dict)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 89, in print_val
    is_tuple_like = False)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 210, in print_struct_val
    body = separator.join([render_child(idx) for idx in range(field_start_index, len(fields))])
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 203, in render_child
    return this + print_val(field_val.get_wrapped_value(), internal_dict)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 89, in print_val
    is_tuple_like = False)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 210, in print_struct_val
    body = separator.join([render_child(idx) for idx in range(field_start_index, len(fields))])
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 203, in render_child
    return this + print_val(field_val.get_wrapped_value(), internal_dict)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 105, in print_val
    return print_std_vec_val(val, internal_dict)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 254, in print_std_vec_val
    internal_dict)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 289, in print_array_of_values
    return ', '.join([render_element(i) for i in range(length)])
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 287, in render_element
    return print_val(element_val, internal_dict)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 89, in print_val
    is_tuple_like = False)
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 210, in print_struct_val
    body = separator.join([render_child(idx) for idx in range(field_start_index, len(fields))])
  File "/Users/alex/Software/rust-devel/src/etc/lldb_rust_formatters.py", line 203, in render_child
    return this + print_val(field_val.get_wrapped_value(), internal_dict)
TypeError: cannot concatenate 'str' and 'NoneType' objects
error: librustc_driver-f561ecb0e4be7b67.dylib DWARF DIE at 0x076fab13 (class closure) has a member variable 0x076fab1a (__0) whose type is a forward declaration, not a complete definition.
Try compiling the source file with -fstandalone-debug
Illegal instruction: 4

[nbigaouette]

I have a similar (the same?) issue when trying to print a PathBuf when debugging.

This issue looks quite similar to #48462, probably a duplicate? Searching issues/pr for lldb_rust_formatters.py typeerror reveals a couple of hits.

I can see the vec![] content of the PathBuf if I print directory.inner.inner.

[nbigaouette]

Similarly to #22656 here's a MRE:

debug.rs:

fn main() {
    let v = vec![1, 2, 3];
    let p = std::path::PathBuf::from("/usr/bin");
    println!("v: {:?}", v);
    println!("p: {:?}", p);
}

rustc -g debug.rs
rust-lldb debug

Now from inside rust-lldb:

(lldb) b debug.rs:4
Breakpoint 1: 2 locations.
(lldb) r
Process 70294 launched: '/var/folders/3z/mjcq38mx3610kl4gnt9zw3gw0000gn/T/tmp.GzBm67H2/debugtest/main' (x86_64)
Process 70294 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
    frame #0: 0x0000000100002ad3 main`main::main::h9e0ea2b04575dfdb at main.rs:4:4
   1   	fn main() {
   2   	    let v = vec![1, 2, 3];
   3   	    let p = std::path::PathBuf::from("/usr/bin");
-> 4   	    println!("v: {:?}", v);
   5   	    println!("p: {:?}", p);
   6   	}
Target 0: (main) stopped.
(lldb) p v
(alloc::vec::Vec<int>) $0 = vec![1, 2, 3]
(lldb) p p
Traceback (most recent call last):
  File "/Users/nbigaouette/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/etc/lldb_rust_formatters.py", line 89, in print_val
    is_tuple_like = False)
  File "/Users/nbigaouette/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/etc/lldb_rust_formatters.py", line 210, in print_struct_val
    body = separator.join([render_child(idx) for idx in range(field_start_index, len(fields))])
  File "/Users/nbigaouette/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/etc/lldb_rust_formatters.py", line 203, in render_child
    return this + print_val(field_val.get_wrapped_value(), internal_dict)
TypeError: cannot concatenate 'str' and 'NoneType' objects
(std::path::PathBuf) $1 = {
  inner = None
}