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Node.js v10.x+ C++ plugin for the LLDB debugger.

The llnode plugin adds the ability to inspect JavaScript stack frames, objects, source code and more to the standard C/C++ debugging facilities when working with Node.js processes or core dumps in LLDB.

Demo

https://asciinema.org/a/29589

Quick start

Start an LLDB session with the llnode plugin automatically loaded:

npm install -g llnode
llnode `which node` -c /path/to/core/dump

Install Instructions

Prerequisites: Official, active Node.js version

llnode only supports currently active Node.js versions installed via official channels. We recommend installing Node.js with nvm as it allows users to install global packages without sudo by default, and it always installs the official executables from https://nodejs.org.

Do not install Node.js from the default Ubuntu/Debian apt repositories (or from the default repositories of other Linux distributions), llnode is not compatible with Node.js installed that way. If you still want to install Node.js via apt-get, take a look at nodesource/distributions.

Prerequisites: Install LLDB and its Library

To use llnode you need to have the LLDB debugger installed. The recommended version is LLDB 3.9 and above.

Install the Plugin

Install llnode globally via npm

If you have lldb available on your PATH, simply run:

npm install -g llnode

To build llnode against a specific lldb version matching an lldb executable, use the --lldb_exe npm option. For example, on Linux the executable on the PATH might be lldb-3.9:

npm install --lldb_exe=`which lldb-3.9` -g llnode

After installing with npm, llnode should be available on your PATH as a shortcut for running LLDB with the llnode plugin.

Optional: Install with Homebrew (OS X/macOS)

brew install llnode

Loading the llnode Plugin

There are several ways to load the llnode plugin:

1. Using the llnode shortcut

If you install llnode globally via npm (npm install -g llnode), you can use the llnode shortcut script. This starts lldb and automatically issues the plugin load command. All parameters to the llnode script are passed directly to lldb. If you it's not a local installation, the shortcut will be in node_modules/.bin/llnode.

2. Using ~/.lldbinit to load the Plugin Automatically

To tell LLDB to load llnode automatically regardless of the version of lldb that you are running, add this line to ~/.lldbinit:

plugin load /path/to/the/llnode/plugin

The path to the llnode plugin should be printed when the installation is finished. On OS X/macOS the plugin is typically node_modules/llnode/llnode.dylib, on Linux it's node_modules/llnode/llnode.so.

3. Loading the Plugin Manually

The llnode plugin can also be manually loaded into LLDB using the plugin load command within lldb.

It does not matter whether the plugin load command is issued before or after loading a core dump or attaching to a process.

4. Install the Plugin to the LLDB System Plugin Directory

Similar to the ~/.lldbinit approach, this way LLDB will also load the plugin automatically on start-up. Doing this may require additional permissions to be able to copy the plugin library to the system plugin directory.

On Linux, run make install-linux in the project directory, or if installing with npm, copy node_modules/llnode/llnode.so to /usr/lib/lldb/plugins or create a link there.

On OS X/macOS, run make install-osx in the project directory, or if installing with npm, copy node_modules/llnode/llnode.dylib to ~/Library/Application\ Support/LLDB/PlugIns/ or create a link there.

Usage

To use llnode with a core dump the core dump needs to be loaded into lldb along with the exact executable that created the core dump. The executable contains information that lldb and the llnode plugin need to make sense of the data in the core dump.

To load a core dump when starting llnode use:

llnode /path/to/bin/node -c /path/to/core

or to load the core dump after starting lldb:

(llnode) target create /path/to/bin/node -c /path/to/core

To use llnode against a live process:

llnode -- /path/to/bin/node script.js
(llnode) run

This is ideal for debugging an npm package with native code. To debug a Node.js crash on uncaught exception:

llnode -- /path/to/bin/node --abort_on_uncaught_exception script.js
(llnode) run

lldb will stop your process when it crashes. To see where it stopped use the v8 bt command. See the Commands section below for more commands.

Commands

(llnode) v8 help
     Node.js helpers

Syntax: v8

The following subcommands are supported:

      bt              -- Show a backtrace with node.js JavaScript functions and their args. An optional argument is accepted; if
                         that argument is a number, it specifies the number of frames to display. Otherwise all frames will be
                         dumped.

                         Syntax: v8 bt [number]
      findjsinstances -- List every object with the specified type name.
                         Use -v or --verbose to display detailed `v8 inspect` output for each object.
                         Accepts the same options as `v8 inspect`
      findjsobjects   -- List all object types and instance counts grouped by typename and sorted by instance count. Use
                         -d or --detailed to get an output grouped by type name, properties, and array length, as well as
                         more information regarding each type.
      findrefs        -- Finds all the object properties which meet the search criteria.
                         The default is to list all the object properties that reference the specified value.
                         Flags:

                          * -v, --value expr     - all properties that refer to the specified JavaScript object (default)
                          * -n, --name  name     - all properties with the specified name
                          * -s, --string string  - all properties that refer to the specified JavaScript string value

      getactivehandles  -- Print all pending handles in the queue. Equivalent to running process._getActiveHandles() on
                           the living process.

      getactiverequests -- Print all pending requests in the queue. Equivalent to running process._getActiveRequests() on
                           the living process.

      inspect         -- Print detailed description and contents of the JavaScript value.

                         Possible flags (all optional):

                          * -F, --full-string    - print whole string without adding ellipsis
                          * -m, --print-map      - print object's map address
                          * -s, --print-source   - print source code for function objects
                          * -l num, --length num - print maximum of `num` elements from string/array

                         Syntax: v8 inspect [flags] expr
      nodeinfo        -- Print information about Node.js
      print           -- Print short description of the JavaScript value.

                         Syntax: v8 print expr
      source list     -- Print source lines around the currently selected
                         JavaScript frame.
                         Syntax: v8 source list [flags]
                         Flags:
                         * -l <line> - Print source code below line <line>.

For more help on any particular subcommand, type 'help <command> <subcommand>'.

Develop and Test

Configure and Build

The easiest way to build the plugin:

# Clone this repo
git clone https://github.com/nodejs/llnode.git && cd llnode

# Configure and build the plugin with npm
npm install
# To configure and build the plugin without npm
node scripts/configure.js && node scripts/install.js && node scripts/cleanup.js
# Or use make
make plugin

# To configure and build both the plugin and the addon
npm install --llnode_build_addon=true
# To configure and build with a specific path to headers
npm install --llnode_lldb_include_dir=/path/to/lldb/include

# Without npm
LLNODE_BUILD_ADDON=true node scripts/configure.js && node scripts/install.js && node scripts/cleanup.js
# Or use make
make addon # Builds the addon
make       # Builds both the addon and the plugin

To configure the build yourself:

# Detect available lldb installation and download headers if necessary
node scripts/configure.js
# To build the addon, set the environment variable LLNODE_BUILD_ADDON=true

# To configure with the detected lldb installation
node-gyp configure
# To configure with a specified path to headers, where `$lldb_include_dir`
# contains the <lldb/*/*.h> headers
node-gyp configure -- -Dlldb_include_dir=/usr/local/Cellar/llvm/5.0.0/include
# To configure with a specified path to the libraries, where `$lldb_lib_dir`
# contains `liblldb.so` or `liblldb.dylib`
node-gyp configure -- -Dlldb_lib_dir=/usr/lib/llvm-3.9/lib

# Build the plugin (and the addon if LLNODE_BUILD_ADDON=true)
node-gyp build

# Move the built plugin to the project directory
node scripts/cleanup.js

Test

To run the tests, if lldb is an executable on the PATH:

npm run test-all    # Run both addon and plugin tests
npm run test-plugin # Run plugin tests
npm run test-addon    # Run addon tests

If the LLDB executable is named differently, point TEST_LLDB_BINARY to it before running the tests:

TEST_LLDB_BINARY=`which lldb-4.0` npm run test-all

Useful Environment Variables

For example, to inspect the process of inspect-scenario.js, run:

LLNODE_DEBUG=true lldb -- \
  node --abort_on_uncaught_exception --expose_externalize_string \
  test/fixtures/inspect-scenario.js
(lldb) run

To debug test/scan-test.js with a prepared core dump:

LLNODE_DEBUG=true TEST_LLNODE_DEBUG=true \
  LLNODE_CORE=/path/to/core/dump/of/inspect/scenario.js \
  LLNODE_NODE_EXE=/path/to/node \
  node test/scan-test.js

LICENSE

This software is licensed under the MIT License.

Copyright Fedor Indutny, 2016.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.