Hi Joe, was thinking of messing with the memory allocator yes. maybe there are other areas also, but the memory allocator would be a good place to start.

This could be a compile time option for python, maybe a module thats only built in debug mode, or a seperate option.

import CAPIForceError CAPIForceError.setmemfail(0.01)

...test the apis error stability...

So python could initialize etc without failing, and the test code would have to set the error probability before it runs a script that tests the api.

Joe Eagar wrote:

One thing you could do is hack the python allocator to fail every once in a while. However, this is likely to cause problems within python itself, along with problems with a python api codebase.

The allocator is in Objects/obmalloc.c in the python source, iirc.

Joe

Campbell Barton wrote:

...

In the Python C api is that your supposed to check every operation succeeds. - Append, a new list, a new float etc.

This makes sense, since somebody could append to a list until the system is out of memory.. or whatever.

The thing that bothers me is theres no good way to test the error cases.

For example in Blender3D and PyGame (the only 2 C API's I'v looked at)

• many checks for failed operations are missing. so its possible somebody could run out of ram and crash the API with python.

for Blender3D or PyGame it probably dosnt matter a great deal, but in other cases, you'd want to make sure that doing crazy stuff within an exception (for example) wont crash the application. Not just to look at the code and think it should work but actually run the error case.

Is there any way to do this?

I was thinking there could be a debug mode where python/C API functions like PyObject_New, PyList_Append etc randomly fail a percentage of the time.

Then you could run unit tests in a debugger and any crashes could be traced. This isnt an exact approach but if the unit tests run enough times you could be fairly sure its well tested (assuming the unit tests cover the API).

Anyone tried this before or does something like this already exist?

-- Campbell J Barton (ideasman42)