New issue 2114: cffi callback function pointer become invalid
https://bitbucket.org/pypy/pypy/issues/2114/cffi-callback-function-pointer-become
Ethan Huang:
Hi,
We embeded Pypy in C++ code, and used the callback function pointer to execute
Python function.
And we noticed that, the callback function pointers might become invalid as the
memory usage grows.
Here is the piece of test code:
for(int i = 0; i < LOOP; i++){
//read python code from file
char* pyBuffer = readPyFile("test_Lower.py");
pypy_execute_source_ptr(pyBuffer, &ptr);
callers[i] = ptr.pyPtrs[0];
}
//check 1st function pointer and call python function
caller = callers[0];
ret = (*((char *(*)(char *))caller))("A");
printf("%s\n", ret);
In the experiment, if the LOOP >150, caller becomes invalid, the callback to
python function could not succeed, and "Segmentation fault" error was reported.
For more complex Python function, the valid LOOP might be smaller.
I am wondering whether the error was caused by GC in Pypy that recycled the
function pointers.
In python fill_api() code, I have used a gloabl list to append function
pointer, but it did not help.
#global list
no_gc = []
def fill_api(ptr):
api = ffi.cast("struct pypyAPI*", ptr)
api.pyPtrs[0] = test_Lower
no_gc.append(api)
no_gc.append(test_Lower)
return api
And are there any methods to prevent such errors?
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