[Solved]Segfault after adding variable to a class of PandaAi

Compiling or Editing the Panda Source
1

Hi community!. I’m working with the PandaAi library, trying to implement some changes. The problem that i am facing is a segmentation fault, after adding just a variable of type double in the class AiCharacter, an initializing it in the constructor with an arbitrary number. The name of the variable is _elapTime. The code looks like this:
in aiCharacter.h:

class AICharacter {
 public:
  double _elapTime;

and in aiCharacter.cxx:

AICharacter::AICharacter(string model_name, NodePath model_np, double mass, double movt_force, double max_force) {
	_elapTime = 0.0;
}

I was having also a segmentation fault working with variables allocated in the heap, using the malloc system call, but after reading this: panda3d.org/dox/python/html/ … l#_details

i started to fallback to the beginning of the development, and observed that the problem is still present under the simple declaration-initialization of that variable of type double. To compile the library i’m using all the steps of the compilation process of the entire Panda3D game engine: i extracted the flags of the call to interrogate, interrogate_module and g++ (to compile and link). I tried the process of compilation of the library without modifications, and it works fine. All the nightmare starts after adding my numeric variable. I am working under Ubuntu 11.10 64 bits. Does anybody have any idea about why i’m having such a segfault?, must i try first to learn how to debug with gdb that piece of code in c++ in order to obtain a trace of the segfault that will certainly make clear the error?. I have no idea of how to debug in this situation (my game is in python, and i need to debug a c++ library of Panda). I searched in the forum about that topic first, but i find some difficulties in order to understand the process of debugging in this setting. But, more important, there is no such a big piece of code to debug!. Thanks in advance!

2

Since adding a new member to a class normally wouldn’t cause a crash, I strongly suspect you’re getting a cross-contamination from some other build of Panda in which this change doesn’t exist. That would cause a crash such as you describe.

Make sure you aren’t inadvertently picking up an .so from a standard build of Panda. To be completely sure, maybe you should completely uninstall any builds of Panda except for the one you’ve made with this change.

David

3

Thanks for the reply!. Seems like you were right!. As i was making an experiment with the pandaai library, i was working on a very messy environment, working directly on the directory that contains that pandaai library, in the panda3d source code. Also i made a script to reproduce all the interrogate-interrogate_module-g++ process, that makes reference (in the calling to interrogate and g++) to some directories of the panda3d. In particular, there was a reference to the directory built/include that also has the headers of the pandaai library (the directory with the original source code of the library pandaai is contrib/src/ai). So i had differents versions of the same headers in the directory built/include and in the directory contrib/src/ai. Making sure that the versions of the headers are the same, seems to be enough to solve the problem. Next step: clean up this mess. Thanks very much for your help!