https://github.com/kastiglione/swift_po

Substitute po for Swift
https://github.com/kastiglione/swift_po

lldb swift

Last synced: about 1 month ago
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Substitute po for Swift

• Host: GitHub
• URL: https://github.com/kastiglione/swift_po
• Owner: kastiglione
• License: mit
• Created: 2018-10-31T18:05:42.000Z (over 6 years ago)
• Default Branch: master
• Last Pushed: 2022-08-06T23:27:45.000Z (over 2 years ago)
• Last Synced: 2025-01-11T07:47:44.990Z (about 1 month ago)
• Topics: lldb, swift
• Language: Python
• Size: 8.79 KB
• Stars: 153
• Watchers: 6
• Forks: 9
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# swift_po aka `spo`

Substitute `po` command for Swift, with fewer corner cases to watch out for.

* ✓ Avoids [memory leaks](#avoids-leaks) caused by lldb

* ✓ Automatically [uses `frame variable`](#frame-variable) (`vo`) if possible

* ✓ Supports [object addresses](#object-pointers), even in Swift

### Avoids Leaks

There's a bug in lldb that creates strong references to any object printed with `po`. The result is leaked objects, and missing calls to `deinit`.

```

(lldb) po self

```

After running this, `self` will never be released. This is not specific to `self`, it happens to any object. A leak will also happen when using `p` or `expression`.

There are two work arounds:

1. [`frame variable -O`](#frame-variable)

2. `call print(...)`

These are what `swift_po` does for you. If the input can be resolved as a variable, then `frame variable` is used, otherwise it performs `call print(...)`.

### frame variable

LLDB has added a `vo` command, an alias for `frame variable -O`. This much like `po`, but is for variable expressions only, not arbitrary code evaluation. Printing via `vo` is faster than `po`. When using `swift_po`, the first option is perform a `vo` operaton. If that fails, `call print(...)` is performed instead.

### Object Pointers

From Swift, `po 0x76543210` will not work. This does work from objc though. `swift_po` works with memory addresses too, same as objc.

### Installation

First clone `swift_po`:

```sh

git clone https://github.com/kastiglione/swift_po.git

```

Next, edit your `~/.lldbinit` to `import` the `spo` command:

```

command script import path/to/swift_po/spo.py

```

### Usage

Call `spo` anywhere you'd normally call `po`.

If you would like to override `po` to be `spo`, add these to your `~/.lldbinit`:

```

command unalias po

command alias po spo

```

### What `swift_po` is doing

A summary of what `swift_po` does for you.

| `spo` command | equivalent lldb |

| - | - |

| `spo 0x76543210` | `expression -l objc -O -- 0x76543210` |

| `spo self` | `frame variable -O self` |

| `spo self.objects` | `frame variable -O self.objects` |

| `spo self.view` | `expression print(self.view)` |

| `spo some.function()` | `expression print(some.function())` |

This table show that some properties cannot be accessed using `frame variable`, in those cases `print()` is used instead.