[all-commits] [llvm/llvm-project] 3328ee: [lldb] Suppress persistent result when running po

[Dave Lee via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3328ee550c86458ade5b3daf5fb4ad97b6a99e6c
      https://github.com/llvm/llvm-project/commit/3328ee550c86458ade5b3daf5fb4ad97b6a99e6c
  Author: Dave Lee <davelee.com at gmail.com>
  Date:   2023-02-16 (Thu, 16 Feb 2023)

  Changed paths:
    M lldb/source/Commands/CommandObjectExpression.cpp
    A lldb/test/API/commands/expression/po_persistent_result/Makefile
    A lldb/test/API/commands/expression/po_persistent_result/TestPoPersistentResult.py
    A lldb/test/API/commands/expression/po_persistent_result/main.m

  Log Message:
  -----------
  [lldb] Suppress persistent result when running po

Remove the persistent result variable after executing `po`.

Without this change, the following behavior happens:

```
(lldb) p thing
(NSObject *) $0 = 0x600000008000
(lldb) po thing
<NSObject: 0x600000008000>
(lldb) p thing
(NSObject *) $2 = 0x600000008000
(lldb) p $1
(NSObject *) $1 = 0x600000008000
```

Even though `po` hides the persistent result variable, it's still created - as $1 in
this example. It can be accessed even though its existence is not evident.

With this change, the persistent result is removed after the object description has
printed. Instead, this is the behavior:

```
(lldb) p thing
(NSObject *) $0 = 0x600000008000
(lldb) po thing
<NSObject: 0x600000008000>
(lldb) p thing
(NSObject *) $1 = 0x600000008000
```

The difference here is that the `po` doens't silently create a persistent result.

Differential Revision: https://reviews.llvm.org/D144044