Skip to content

Commit

Permalink
[lldb-dap][docs] Improve README (#109266)
Browse files Browse the repository at this point in the history 
* Document how to procure and configure the `lldb-dap` binary
* Improve documentation for `launch.json`:
* Show the examples before the reference. Most new users just want to
get going, and will only need the reference later on
   * Deduplicate the list of "launch" and "attach" config settings
* Remove the `stopOnEntry` setting from "attach", since this is a
launch-only setting
* Document the previously undocumented settings `sourcePath`,
`commandEscapePrefix`, `custom{Frame,Thread}Format`, `runInTerminal`
* Add the settings `debuggerRoot` and `sourceMap` to the common section.
So far they were documented as launch-only settings.
* Document that the Debug Console prints variables / expressions by
default and that LLDB commands need to be escaped.
  • Loading branch information
@vogelsgesang
vogelsgesang authored Sep 20, 2024
1 parent d8d252f commit 65c5706
Showing 1 changed file with 92 additions and 70 deletions.
162 changes: 92 additions & 70 deletions lldb/tools/lldb-dap/README.md
View file
Original file line number Diff line number Diff line change
@@ -1,77 +1,30 @@
# LLDB DAP

## `lldb-dap` Configurations
## Procuring the `lldb-dap` binary

The extension requires the `lldb-dap` (formerly `lldb-vscode`) binary. It is a
command line tool that implements the [Debug Adapter
Protocol](https://microsoft.github.io/debug-adapter-protocol/). It is used to power the Visual Studio Code extension but can also be used with other IDEs and editors that support DAP.
The protocol is easy to run remotely and also can allow other tools and IDEs to
get a full featured debugger with a well defined protocol.
The extension requires the `lldb-dap` (formerly `lldb-vscode`) binary.
This binary is not packaged with the VS Code extension.

## Launching & Attaching Configuration
There are multiple ways to obtain this binary:
* build it from source (see [LLDB's build instructions](https://lldb.llvm.org/resources/build.html))
* download it one of the relase packages from the [LLVM release page](https://github.com/llvm/llvm-project/releases/). The `LLVM-19.1.0-{operating_system}.tar.xz` packages contain a prebuilt `lldb-dap` binary.
* use the binary provided by your toolchain (for example `xcrun -f lldb-dap` on macOS) or contact your toolchain vendor to include it.

Launching to attaching require you to create a [launch configuration](https://code.visualstudio.com/Docs/editor/debugging#_launch-configurations).
This file defines arguments that get passed to `lldb-dap` and the configuration settings control how the launch or attach happens.

### Launch Configuration Settings

When you launch a program with Visual Studio Code you will need to create a [launch.json](https://code.visualstudio.com/Docs/editor/debugging#_launch-configurations)
file that defines how your program will be run. The JSON configuration file can contain the following `lldb-dap` specific launch key/value pairs:

|parameter |type|req | |
|-------------------|----|:--:|---------|
|**name** |string|Y| A configuration name that will be displayed in the IDE.
|**type** |string|Y| Must be "lldb-dap".
|**request** |string|Y| Must be "launch".
|**program** |string|Y| Path to the executable to launch.
|**args** |[string]|| An array of command line argument strings to be passed to the program being launched.
|**cwd** |string| | The program working directory.
|**env** |dictionary| | Environment variables to set when launching the program. The format of each environment variable string is "VAR=VALUE" for environment variables with values or just "VAR" for environment variables with no values.
|**stopOnEntry** |boolean| | Whether to stop program immediately after launching.
|**initCommands** |[string]| | LLDB commands executed upon debugger startup prior to creating the LLDB target. Commands and command output will be sent to the debugger console when they are executed.
|**preRunCommands** |[string]| | LLDB commands executed just before launching after the LLDB target has been created. Commands and command output will be sent to the debugger console when they are executed.
|**stopCommands** |[string]| | LLDB commands executed just after each stop. Commands and command output will be sent to the debugger console when they are executed.
|**launchCommands** |[string]| | LLDB commands executed to launch the program. Commands and command output will be sent to the debugger console when they are executed.
|**exitCommands** |[string]| | LLDB commands executed when the program exits. Commands and command output will be sent to the debugger console when they are executed.
|**terminateCommands** |[string]| | LLDB commands executed when the debugging session ends. Commands and command output will be sent to the debugger console when they are executed.
|**sourceMap** |[string[2]]| | Specify an array of path re-mappings. Each element in the array must be a two element array containing a source and destination pathname.
|**debuggerRoot** | string| |Specify a working directory to use when launching lldb-dap. If the debug information in your executable contains relative paths, this option can be used so that `lldb-dap` can find source files and object files that have relative paths.
|**enableAutoVariableSummaries**|bool| | Enable auto generated summaries for variables when no summaries exist for a given type. This feature can cause performance delays in large projects when viewing variables.
|**enableDisplayExtendedBacktrace**|bool| | Enable language specific extended backtraces.
|**enableSyntheticChildDebugging**|bool| | If a variable is displayed using a synthetic children, also display the actual contents of the variable at the end under a [raw] entry. This is useful when creating sythetic child plug-ins as it lets you see the actual contents of the variable.

### Attaching Settings
By default, the VS Code extension will expect to find `lldb-dap` in your `PATH`.
Alternatively, you can explictly specify the location of the `lldb-dap` binary using the `lldb-dap.executable-path` setting.

When attaching to a process using LLDB you can attach in a few ways
### Usage with other IDEs

1. Attach to an existing process using the process ID
2. Attach to an existing process by name
3. Attach by name by waiting for the next instance of a process to launch
The `lldb-dap` binary is a command line tool that implements the [Debug Adapter Protocol](https://microsoft.github.io/debug-adapter-protocol/).
It is used to power the VS Code extension but can also be used with other IDEs and editors that support DAP.
The protocol is easy to run remotely and also can allow other tools and IDEs to get a full featured debugger with a well defined protocol.

The JSON configuration file can contain the following `lldb-dap` specific launch key/value pairs:

|parameter |type |req | |
|-------------------|--------|:--:|---------|
|**name** |string |Y| A configuration name that will be displayed in the IDE.
|**type** |string |Y| Must be "lldb-dap".
|**request** |string |Y| Must be "attach".
|**program** |string | | Path to the executable to attach to. This value is optional but can help to resolve breakpoints prior the attaching to the program.
|**pid** |number | | The process id of the process you wish to attach to. If **pid** is omitted, the debugger will attempt to attach to the program by finding a process whose file name matches the file name from **porgram**. Setting this value to `${command:pickMyProcess}` will allow interactive process selection in the IDE.
|**stopOnEntry** |boolean| | Whether to stop program immediately after launching.
|**waitFor** |boolean | | Wait for the process to launch.
|**initCommands** |[string]| | LLDB commands executed upon debugger startup prior to creating the LLDB target. Commands and command output will be sent to the debugger console when they are executed.
|**preRunCommands** |[string]| | LLDB commands executed just before launching after the LLDB target has been created. Commands and command output will be sent to the debugger console when they are executed.
|**stopCommands** |[string]| | LLDB commands executed just after each stop. Commands and command output will be sent to the debugger console when they are executed.
|**exitCommands** |[string]| | LLDB commands executed when the program exits. Commands and command output will be sent to the debugger console when they are executed.
|**terminateCommands** |[string]| | LLDB commands executed when the debugging session ends. Commands and command output will be sent to the debugger console when they are executed.
|**attachCommands** |[string]| | LLDB commands that will be executed after **preRunCommands** which take place of the code that normally does the attach. The commands can create a new target and attach or launch it however desired. This allows custom launch and attach configurations. Core files can use `target create --core /path/to/core` to attach to core files.
|**enableAutoVariableSummaries**|bool| | Enable auto generated summaries for variables when no summaries exist for a given type. This feature can cause performance delays in large projects when viewing variables.
|**enableDisplayExtendedBacktrace**|bool| | Enable language specific extended backtraces.
|**enableSyntheticChildDebugging**|bool| | If a variable is displayed using a synthetic children, also display the actual contents of the variable at the end under a [raw] entry. This is useful when creating sythetic child plug-ins as it lets you see the actual contents of the variable.
## Launching & Attaching to a debugee

### Example configurations
Launching or attaching a debugee require you to create a [launch configuration](https://code.visualstudio.com/Docs/editor/debugging#_launch-configurations).
This file defines arguments that get passed to `lldb-dap` and the configuration settings control how the launch or attach happens.

#### Launching
### Launching a debugee

This will launch `/tmp/a.out` with arguments `one`, `two`, and `three` and
adds `FOO=1` and `bar` to the environment:
Expand All @@ -87,6 +40,14 @@ adds `FOO=1` and `bar` to the environment:
}
```

### Attaching to a process

When attaching to a process using LLDB, you can attach in multiple ways:

1. Attach to an existing process using the process ID
2. Attach to an existing process by name
3. Attach by name by waiting for the next instance of a process to launch

#### Attach using PID

This will attach to a process `a.out` whose process ID is 123:
Expand Down Expand Up @@ -132,7 +93,7 @@ to be launched you can add the "waitFor" key value pair:
This will work as long as the architecture, vendor and OS supports waiting
for processes. Currently MacOS is the only platform that supports this.

#### Loading a Core File
### Loading a Core File

This loads the coredump file `/cores/123.core` associated with the program
`/tmp/a.out`:
Expand All @@ -147,7 +108,7 @@ This loads the coredump file `/cores/123.core` associated with the program
}
```

#### Connect to a Debug Server on the Current Machine
### Connect to a Debug Server on the Current Machine

This connects to a debug server (e.g. `lldb-server`, `gdbserver`) on
the current machine, that is debugging the program `/tmp/a.out` and listening
Expand Down Expand Up @@ -177,7 +138,7 @@ instead of using the custom command `attachCommands`.
}
```

#### Connect to a Debug Server on Another Machine
### Connect to a Debug Server on Another Machine

This connects to a debug server running on another machine with hostname
`hostnmame`. Which is debugging the program `/tmp/a.out` and listening on
Expand Down Expand Up @@ -210,12 +171,73 @@ The default hostname being used `localhost`.
}
```

## Custom debugger commands
### Configuration Settings Reference

For both launch and attach configurations, lldb-dap accepts the following `lldb-dap`
specific key/value pairs:

|parameter |type|req | |
|-------------------|----|:--:|---------|
|**name** |string|Y| A configuration name that will be displayed in the IDE.
|**type** |string|Y| Must be "lldb-dap".
|**request** |string|Y| Must be "launch" or "attach".
|**program** |string|Y| Path to the executable to launch.
|**sourcePath** |string| | Specify a source path to remap \"./\" to allow full paths to be used when setting breakpoints in binaries that have relative source paths.
|**sourceMap** |[string[2]]| | Specify an array of path re-mappings. Each element in the array must be a two element array containing a source and destination pathname. Overrides sourcePath.
|**debuggerRoot** | string| |Specify a working directory to use when launching lldb-dap. If the debug information in your executable contains relative paths, this option can be used so that `lldb-dap` can find source files and object files that have relative paths.
|**commandEscapePrefix** | string | | The escape prefix to use for executing regular LLDB commands in the Debug Console, instead of printing variables. Defaults to a back-tick (`\``). If it's an empty string, then all expression in the Debug Console are treated as regular LLDB commands.
|**customFrameFormat** | string | | If non-empty, stack frames will have descriptions generated based on the provided format. See https://lldb.llvm.org/use/formatting.html for an explanation on format strings for frames. If the format string contains errors, an error message will be displayed on the Debug Console and the default frame names will be used. This might come with a performance cost because debug information might need to be processed to generate the description.
|**customThreadFormat** | string | | Same as `customFrameFormat`, but for threads instead of stack frames.
|**enableAutoVariableSummaries**|bool| | Enable auto generated summaries for variables when no summaries exist for a given type. This feature can cause performance delays in large projects when viewing variables.
|**enableDisplayExtendedBacktrace**|bool| | Enable language specific extended backtraces.
|**enableSyntheticChildDebugging**|bool| | If a variable is displayed using a synthetic children, also display the actual contents of the variable at the end under a [raw] entry. This is useful when creating sythetic child plug-ins as it lets you see the actual contents of the variable.
|**initCommands** |[string]| | LLDB commands executed upon debugger startup prior to creating the LLDB target.
|**preRunCommands** |[string]| | LLDB commands executed just before launching/attaching, after the LLDB target has been created.
|**stopCommands** |[string]| | LLDB commands executed just after each stop.
|**exitCommands** |[string]| | LLDB commands executed when the program exits.
|**terminateCommands** |[string]| | LLDB commands executed when the debugging session ends.

All commands and command outputs will be sent to the debugger console when they are executed.
Commands can be prefixed with `?` or `!` to modify their behavior:
* Commands prefixed with `?` are quiet on success, i.e. nothing is written to stdout if the command succeeds.
* Prefixing a command with `!` enables error checking: If a command prefixed with `!` fails, subsequent commands will not be run. This is usefule if one of the commands depends on another, as it will stop the chain of commands.

For JSON configurations of `"type": "launch"`, the JSON configuration can additionally
contain the following key/value pairs:

|parameter |type|req | |
|-------------------|----|:--:|---------|
|**program** |string|Y| Path to the executable to launch.
|**args** |[string]|| An array of command line argument strings to be passed to the program being launched.
|**cwd** |string| | The program working directory.
|**env** |dictionary| | Environment variables to set when launching the program. The format of each environment variable string is "VAR=VALUE" for environment variables with values or just "VAR" for environment variables with no values.
|**stopOnEntry** |boolean| | Whether to stop program immediately after launching.
|**runInTerminal** |boolean| | Launch the program inside an integrated terminal in the IDE. Useful for debugging interactive command line programs.
|**launchCommands** |[string]| | LLDB commands executed to launch the program.

For JSON configurations of `"type": "attach"`, the JSON configuration can contain
the following `lldb-dap` specific key/value pairs:

|parameter |type |req | |
|-------------------|--------|:--:|---------|
|**program** |string | | Path to the executable to attach to. This value is optional but can help to resolve breakpoints prior the attaching to the program.
|**pid** |number | | The process id of the process you wish to attach to. If **pid** is omitted, the debugger will attempt to attach to the program by finding a process whose file name matches the file name from **porgram**. Setting this value to `${command:pickMyProcess}` will allow interactive process selection in the IDE.
|**waitFor** |boolean | | Wait for the process to launch.
|**attachCommands** |[string]| | LLDB commands that will be executed after **preRunCommands** which take place of the code that normally does the attach. The commands can create a new target and attach or launch it however desired. This allows custom launch and attach configurations. Core files can use `target create --core /path/to/core` to attach to core files.

## Debug Console

The debug console allows printing variables / expressions and executing lldb commands.
By default, all provided commands are interpreteted as variable names / expressions whose values will be printed to the Debug Console.
To execute regular LLDB commands, prefix them with the `\`` character.
The escape character can be changed via the `commandEscapePrefix` configuration option.

### lldb-dap specific commands

The `lldb-dap` tool includes additional custom commands to support the Debug
Adapter Protocol features.

### startDebugging
#### `lldb-dap startDebugging`

Using the command `lldb-dap startDebugging` it is possible to trigger a
reverse request to the client requesting a child debug session with the
Expand All @@ -240,7 +262,7 @@ This will launch a server and then request a child debug session for a client.
}
```

### repl-mode
#### `lldb-dap repl-mode`

Inspect or adjust the behavior of lldb-dap repl evaluation requests. The
supported modes are `variable`, `command` and `auto`.
Expand Down

0 comments on commit 65c5706

Please sign in to comment.