Devtools

Unopinionated tools for running, debugging and testing Mojo apps.

Install

git clone https://github.com/domokit/devtools.git

Contents

Devtools offers the following tools:

• mojo_run - shell runner
• mojo_test - apptest runner
• mojo_debug - debugger supporting interactive tracing and debugging of a running mojo shell

Additionally, remote_adb_setup script helps to configure adb on a remote machine to communicate with a device attached to a local machine, forwarding the ports used by mojo_run.

Debugger

The mojo_debug script allows you to interactively inspect a running shell, collect performance traces and attach a gdb debugger.

Tracing

To collect performance traces and retrieve the result:

mojo_debug tracing start
mojo_debug tracing stop [result.json]

The trace file can be then loaded using the trace viewer in Chrome available at about://tracing.

GDB

It is possible to inspect a Mojo Shell process using GDB. The mojo_debug script can be used to launch GDB and attach it to a running shell process (android only):

mojo_debug gdb attach

Once started, GDB will first stop the Mojo Shell execution, then load symbols from loaded Mojo applications. Please note that this initial step can take some time (up to several minutes in the worst case).

After each execution pause, GDB will update the set of loaded symbols based on the selected thread only. If you need symbols for all threads, use the update-symbols GDB command:

(gdb) update-symbols

If you only want to update symbols for the current selected thread (for example, after changing threads), use the current option:

(gdb) update-symbols current

Android crash stacks

When Mojo shell crashes on Android (“Unfortunately, Mojo shell has stopped.”) due to a crash in native code, mojo_debug can be used to find and symbolize the stack trace present in the device log:

mojo_debug device stack

devtoolslib

devtoolslib is a Python module containing the core scripting functionality for running Mojo apps: shell abstraction with implementations for Android and Linux and support for apptest frameworks. The executable scripts in devtools are based on this module. One can also choose to embed the functionality provided by devtoolslib in their own wrapper.

Development

The library is canonically developed in the mojo repository, https://github.com/domokit/devtools is a mirror allowing to consume it separately.