[all-commits] [llvm/llvm-project] af0094: [lldb] Fix `thread backtrace --count` (#83602)

[Jonas Devlieghere via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: af009451ec439593554f03bc714e46ad2cd41738
      https://github.com/llvm/llvm-project/commit/af009451ec439593554f03bc714e46ad2cd41738
  Author: Jonas Devlieghere <jonas at devlieghere.com>
  Date:   2024-03-01 (Fri, 01 Mar 2024)

  Changed paths:
    M lldb/source/Commands/CommandObjectThread.cpp
    M lldb/source/Commands/Options.td
    A lldb/test/Shell/Commands/command-thread-backtrace.test

  Log Message:
  -----------
  [lldb] Fix `thread backtrace --count` (#83602)

The help output for `thread backtrace` specifies that you can pass -1 to
`--count` to display all the frames.

```
-c <count> ( --count <count> )
            How many frames to display (-1 for all)
```

However, that doesn't work:

```
(lldb) thread backtrace --count -1
error: invalid integer value for option 'c'
```

The problem is that we store the option value as an unsigned and the
code to parse the string correctly rejects it. There's two ways to fix
this:

1. Make `m_count` a signed value so that it accepts negative values and
appease the parser. The function that prints the frames takes an
unsigned so a negative value will just become a really large positive
value, which is what the current implementation relies on.
2. Keep `m_count` unsigned and instead use 0 the magic value to show all
frames. I don't really see a point in not showing any frames at all,
plus that's already broken (`error: error displaying backtrace for
thread: "0x0001"`).

This patch implements (2) and at the same time improve the error
reporting so that we print the invalid value when we cannot parse it.

rdar://123881767



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