[pypy-dev] pypy callback function pointer become invalid

[Armin Rigo]

Hi Yicong,

On 17 August 2015 at 08:40, Yicong Huang <hengha.mao at gmail.com> wrote:
> yes, we could use a structure to wrap severl python callback function
> pointers in one execution.
> However, the issue is that we might not be able to get all python functions
> that would be executed at the beginning.

The basic idea is to define whatever API you need with just one call
to pypy_execute_source_ptr().  If you want to be able to compile and
execute arbitrary Python functions, just make that feature available
in your API.  This is the same idea as PyRun_SimpleString(), which is
*one* API function but lets you execute arbitrary Python code.
Example:


struct API {
    long (*run_function)(char *);
};
struct API api;   /* global var */

int initialize_api(void) {    /* run this only once */
    static char source[] =
        "import sys; sys.path.insert(0, '.'); "
        "import interface; interface.fill_api(c_argument)";
    pypy_execute_source_ptr(source, &api);
}

/* then execute 'api.run_function(some_source_code)' any number of times */


# file "interface.py"

import cffi

ffi = cffi.FFI()
ffi.cdef('''
struct API {
    long (*run_function)(char *);
};
''')

@ffi.callback("long(char *)")
def run_function(p_src):
    src = ffi.string(p_src)
    # here 'src' is a string, we can do whatever we want with it---like eval()
    return eval(src, {})

def fill_api(ptr):
    global api
    api = ffi.cast("struct API*", ptr)
    api.run_function = run_function


---
Armin