025a99ccbb
The debugger supports setting breakpoints, execution control (step, next, continue) and getting backtrace. The communication is WebSocket-based, so a browser can communicate with JerryScript without any intermediate application. JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com JerryScript-DCO-1.0-Signed-off-by: Levente Orban orbanl@inf.u-szeged.hu
2.9 KiB
JerryScript debugger interface
JerryScript provides a remote debugger which allows debugging JavaScript programs. The debugger has two main components: a server which is part of the JerryScript binary and a separate client application. Currently two debugger clients are available in the /jerry-debugger subdirectory: an HTML and a Python application. These simple applications demonstrate the communication protocol between the client and server and can be reused by integrated development environments.
Setting up the debugger server
The following arguments must be passed to tools/build.py:
--jerry-debugger=on --jerry-libc=off
At the moment only a Websocket-based implementation is provided by JerryScript which transmits messages over TCP/IP networks. This implementation requires a socket API which is not yet supported by jerry-libc so the standard libc is used instead. In the future any reliable stream or datagram based protocol can be used for transmitting debugger messages.
Debugging JavaScript applications
The debugger client must be connected to the server before the JavaScript application runs. On-the-fly attachment is not supported because the debugging information (e.g. line index of each possible breakpoint location) is not preserved by JerryScript. The client is expected to be run on a system with much more resources and it should be capable of storing this information. JerryScript frees all debug information after it is transmitted to the client to save memory.
The following argument makes JerryScript wait for a client connection:
--start-debug-server
It is also recommended to increase the log level to see the Waiting for client connection message:
--log-level 2
The HTML client can connect to the IP address of the server with
the connect command. The IP address can be localhost
if the server and the client are running on the same machine.
After the connection is established the execution can be
controlled by the debugger. The debugger always stops at
the first possible breakpoint location. The effect is the
same as using the stop command. This allows inserting
breakpoints right before the meaningful part of the execution
starts.
All available commands of the client can be queried by the
help command.
Integrating debugger support into applications using JerryScript
The debugger can be enabled by passing the JERRY_INIT_DEBUGGER flag
to the jerry_init () function which then initializes the debugger
and blocks until a client connects.
When the debugger is enabled it is recommended to use
jerry_parse_named_resource () instead of jerry_parse () because
the resource name (usually a file name) is also passed to this
function. This resource name is used by the client to identify
the corresponding resource. In general it is always recommended to
use jerry_parse_named_resource () when the resource name is
available because it silently ignores the resource name if the
debugger is disabled.