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When a ctypes C callback function is called, zero out the result 

storage before converting the result to C data.  See the comment in
the code for details.

Provide a better context for errors when the conversion of a callback
function's result cannot be converted.
This commit is contained in:
Thomas Heller 2006-08-11 19:55:35 +00:00
parent 975c8bb515
commit 2a899c8b76
1 changed files with 17 additions and 7 deletions
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24
Modules/_ctypes/callbacks.c
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@ -205,14 +205,24 @@ if (x == NULL) _AddTraceback(what, __FILE__, __LINE__ - 1), PyErr_Print()
result = PyObject_CallObject(callable, arglist); result = PyObject_CallObject(callable, arglist);
CHECK("'calling callback function'", result); CHECK("'calling callback function'", result);
#ifdef WORDS_BIGENDIAN
/* See the corresponding code in callproc.c, around line 961 */
if (restype->type != FFI_TYPE_FLOAT && restype->size < sizeof(ffi_arg))
mem = (char *)mem + sizeof(ffi_arg) - restype->size;
#endif
/* The code that converts 'result' into C data is not executed when
'callable' returns Py_None, so we zero out the memory that will
receive the C return data to not return random data.
Cleaner would be to call 'setfunc' anyway and complain with
PyErr_WriteUnraisable(), but ctypes has always accepted a Py_None
return value for *any* 'restype' and it would probably break too
much code if this is changed now.
*/
memset(mem, 0, restype->size);
if ((restype != &ffi_type_void) && result && result != Py_None) { if ((restype != &ffi_type_void) && result && result != Py_None) {
PyObject *keep; PyObject *keep;
assert(setfunc); assert(setfunc);
#ifdef WORDS_BIGENDIAN
/* See the corresponding code in callproc.c, around line 961 */
if (restype->type != FFI_TYPE_FLOAT && restype->size < sizeof(ffi_arg))
mem = (char *)mem + sizeof(ffi_arg) - restype->size;
#endif
keep = setfunc(mem, result, 0); keep = setfunc(mem, result, 0);
CHECK("'converting callback result'", keep); CHECK("'converting callback result'", keep);
/* keep is an object we have to keep alive so that the result /* keep is an object we have to keep alive so that the result
@ -225,13 +235,13 @@ if (x == NULL) _AddTraceback(what, __FILE__, __LINE__ - 1), PyErr_Print()
itself knows how to manage the refcount of these objects. itself knows how to manage the refcount of these objects.
*/ */
if (keep == NULL) /* Could not convert callback result. */ if (keep == NULL) /* Could not convert callback result. */
PyErr_WriteUnraisable(Py_None); PyErr_WriteUnraisable(callable);
else if (keep == Py_None) /* Nothing to keep */ else if (keep == Py_None) /* Nothing to keep */
Py_DECREF(keep); Py_DECREF(keep);
else if (setfunc != getentry("O")->setfunc) { else if (setfunc != getentry("O")->setfunc) {
if (-1 == PyErr_Warn(PyExc_RuntimeWarning, if (-1 == PyErr_Warn(PyExc_RuntimeWarning,
"memory leak in callback function.")) "memory leak in callback function."))
PyErr_WriteUnraisable(Py_None); PyErr_WriteUnraisable(callable);
} }
} }
Py_XDECREF(result); Py_XDECREF(result);