跟踪iPhone上的出站访问

Question

I work on an average (~ 20k lines of code, Objective-C mixed with C++), and I am figthing to hunt down an EXC_BAD_ACCESS error.

I have tried all the common techniques (like enabling NSZombie, guard edges,etc.) So far, I have ruled out the possibility to access a released object, and the double-free error.

It seems that something writes on a memory space where it shouldn't. But, as many memory errors, it's not happening all the time, and it's not crashing always in the same place. (Sometimes I receive the "object was modified after being freed" message).

Sometimes, the overwritten memory belongs to the allocator , and it crashes on malloc, or on free().

And, of course, some changes in the app may influence the bug's behaviour - if I try to comment out parts of the code, the error appears less often, so it's more difficult to find it.

Finally, I have been looking into using valgrind , but it seems that all those who used it worked on the simulator. but my code must run on the actual device (some code is ARM -specific)

Are there any general tips on how to debug such errors?

Note: The app involves video processing , so the amount of memory used is fairly large.

Answer 1

There are some special tools available on the XCode. You could try to use them in order to analyse your code. http://developer.apple.com/library/mac/#featuredarticles/StaticAnalysis/index.html It will produce some warning in case of invalid objects usage so it could help you to find a problem.

Answer 2

If you feel that the C++ code is causing the issue you could copy the C++ out of your iPhone project and create a Mac project. With this you could set up various stress tests. And, you should be able to use valgrind as well.