How to debug a native C++ plugin ?

Hi everyone,

I've been struggling quite a lot recently due to my incapacity to easily debug a native C++ plugin. I found a few solutions for windows, but none for Linux. Debugging by manually logging info into a file was okay for a time, but it makes it sometimes really tedious to find some very simple problems. And the very little information that I get from the Unity Log File (if I get any) when Unity crashes is most of the time useless.
Ideally, I would like to use gdb to be able to get all the debug info that I need, but it seems a bit more tricky than I thought. I tried to launch the Unity Editor with gdb without success and I'm pretty much out of ideas.

Did anyone managed to do something similar ?

Thanks a lot in advance .

 

not sure if this is possible, but maybe there is a way to get VSCode to debug native c++ with Unity?

I haven't tried it for C++, but works well with C#.

https://code.visualstudio.com/docs/languages/cpp

 

Hi tswalk,

Thanks a lot for the tip. I'll try it this afternoon and let you know. This might be interesting for a few people.

Thanks again,
Quentrin

 

Okay, so I gave it a try, but it is still not really helping. Basically I can debug my C# code (Using the Unity debugger), but I don't have any info about what's going on in the plugin. So when it crashes I can't get the stack (a simple "backtrace" command with gdb).
As it was not working with the Unity debugger I tried to create a configuration with cppdbg (which uses gdb).
Here is the configuration I added :

{
"name": "C++ Attach",
"type": "cppdbg",
"request": "attach",
"program": "/PathToMyUnityProject/Assets/MyPlugin.so",
"processId": "${command.pickProcess}",
"linux": {
"MIMode": "gdb"
}
}

When I attach the process to Unity I get the following message:
"Source /build/glibc-ryFjv0/glibc-2.21/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S is not available."

And if I try to resume after it paused I get
"Source /build/glibc-ryFjv0/glibc-2.21/sysdeps/unix/syscall-template.S is not available." and so on

Am I doing something wrong ?
I was not sure about the "program" property so I also tried to give the Path to the unity Editor (which I select anyway when attaching the process) and even the path to gdb.

I'm not really used to vscode yet but it feels like the debugging the plugin is possible. Does anyone has a clue of how to do it ?

Thanks a lot,
Quentin.

 

Hello Tak,

Thanks a lot for your answer. I finally managed to launch Unity with gdb by first doing the command
"handle SIGXCPU SIG33 SIG35 SIGPWR nostop noprint"

Sadly I still can't get details with the backtrace command. I usually get this sort of info :
0x00007fffe2fa3792 in ?? ()
0x00007fffe2fa4002 in ?? ()
...
But if I try the mono_pmip command, it only prints
$1 = 0
...
$2 = 0

Am I missing something ?
Thanks a lot again for your help.

 

Hi everyone, I would like to know if there is any chance that it is possible now to debug step by step in native C++ library with Unity Free version and Visual Community?
I was able to do that in 2016 with Unity Pro.
Thanks

 

Since nobody else answered and this was high in my google search: yeah, it's easy - just VS -> "Attach to Process", select "unity.exe", and that's all you need.

To troubleshoot: in VS use the "Modules" pane to verify that your dll is loaded and has symbols. I also set code type to "Native" in the attach dialog.

 

Someone posted a Visual Studio Solution, here's a Rider one.

Run > Attach To Process

And then attach to the Unity process. It looks something like this:
%pid% %unitypath% -projectPath %projectpath% -riderPath %riderpath% -debugCodeOptimizations.

Do not use Attach To Unity Process as it attaches to Unity's managed debugger, which won't be useful at all.

Something else I learned the hard way: only exported functions will have breakpoints associated with them.