Debugging on Host

Required tools and hardware

For MacOS, GDB can be installed via brew but it requires code-signing. This is not a trivial procedure and lldb is recommended. This is installed with the standard xcode development tools.

For other development platforms the GNU debugger is required. Make sure that you have the following executable in your PATH:

gdb

No additional hardware is required.

Recompilation is required

In order to debug applications based on Sming Framework make sure that you are using Sming version 3.8.0 or newer.

Compilation directives

If you want to debug your application and the Sming Framework code make sure to (re)compile it with ENABLE_GDB=1 directive:

cd $SMING_HOME/../samples/LiveDebug
make components-clean # -- Forces a rebuild of all Components
make ENABLE_GDB=1

The commands above will re-compile Sming with debug symbols and optimizations for debugging. These commands need to be executed once.

If you need to debug the LWIP TCP/IP stack, add ENABLE_LWIPDEBUG when rebuilding:

make ENABLE_GDB=1 ENABLE_LWIPDEBUG=1

Application

To use, (re)compile your application with the ENABLE_GDB option. For this example we will use the Live Debug sample application:

cd $SMING_HOME/../samples/LiveDebug
make ENABLE_GDB=1 # -- recompiles your application with debugging support

The next step is to start the debugger. This can be done with the command below:

make gdb

For MacOS, use lldb:

make lldb

After that a new interactive debugging session will be started:

Welcome to SMING!
Type 'r' to run application

To start the execution of the application type r or run:

(gdb) r
Starting program: /x/Sming/samples/LiveDebug/out/Host/debug/firmware/app --flashfile=out/Host/debug/firmware/flash.bin --flashsize=4M --pause
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1".
[New Thread 0xf7bdcb40 (LWP 16428)]

Welcome to the Sming Host emulator

host_flashmem_init: Created blank "out/Host/debug/firmware/flash.bin", 4194304 bytes

...
main: >> Starting Sming <<

You can pause the program execution by pressing Ctrl-C. And work further using some further GDB commands. The next paragraph describes some of them.

GDB commands

For MacOS, please refer to https://lldb.llvm.org/index.html for LLDB usage instructions.

There are multiple commands supported in GDB and we will mention only some of them.

List current source code

One possibility is to see the source code of the current line where the execution has stopped. To achieve this you should type list in the gdb console:

(gdb) list
102     }
103 }
104
105 int main(int argc, char* argv[])
106 {
107     trap_exceptions();
108
109     host_printf("\nWelcome to the Sming Host emulator\n\n");
110
111     static struct {

Break the execution

This command will pause the debugger once it reaches a specific function or line in the code. This is called breakpoint and can be set like this:

(gdb) break blink
Breakpoint 1 at 0x40105d4c: file app/application.cpp, line 66.

Continue the execution

To continue the execution of the application we can use the continue command:

(gdb) continue
Continuing.

Breakpoint 1, blink () at app/application.cpp:66
66 {
(gdb)

Because we have set already a breakpoint for the blink function the execution will be paused when the blink function is reached and from here you can go to the next line or see the current values of the variables.

Go to the next line

This can be done using next:

(gdb) next
67      digitalWrite(LED_PIN, ledState);

See variable value

The command to see a value is print followed by the name of the value. For example to see the value of the ledState variable inside the blink function we could type:

(gdb) print ledState
$1 = true

You can see more useful commands here.

Or watch the following short video