[Python-checkins] bpo-46323: Reduce stack usage of ctypes python callback function. (GH-31224)
corona10
webhook-mailer at python.org
Wed Feb 9 13:10:21 EST 2022
https://github.com/python/cpython/commit/d18120cd67b4297f78bfc9bf7b36774cf0bf15f2
commit: d18120cd67b4297f78bfc9bf7b36774cf0bf15f2
branch: main
author: Dong-hee Na <donghee.na at python.org>
committer: corona10 <donghee.na92 at gmail.com>
date: 2022-02-10T03:10:11+09:00
summary:
bpo-46323: Reduce stack usage of ctypes python callback function. (GH-31224)
files:
A Misc/NEWS.d/next/Core and Builtins/2022-02-10-02-29-12.bpo-46323.HK_cs0.rst
M Modules/_ctypes/callbacks.c
M Modules/_ctypes/callproc.c
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-02-10-02-29-12.bpo-46323.HK_cs0.rst b/Misc/NEWS.d/next/Core and Builtins/2022-02-10-02-29-12.bpo-46323.HK_cs0.rst
new file mode 100644
index 0000000000000..16db7c5eaea71
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-02-10-02-29-12.bpo-46323.HK_cs0.rst
@@ -0,0 +1,3 @@
+:mod:`ctypes` now allocates memory on the stack instead of on the heap
+to pass arguments while calling a Python callback function.
+Patch by Dong-hee Na.
diff --git a/Modules/_ctypes/callbacks.c b/Modules/_ctypes/callbacks.c
index f2d9a530e6e38..591b944d76fcb 100644
--- a/Modules/_ctypes/callbacks.c
+++ b/Modules/_ctypes/callbacks.c
@@ -14,9 +14,18 @@
#include <stdbool.h>
+#ifdef MS_WIN32
+# include <malloc.h>
+#endif
+
#include <ffi.h>
#include "ctypes.h"
+#ifdef HAVE_ALLOCA_H
+/* AIX needs alloca.h for alloca() */
+#include <alloca.h>
+#endif
+
/**************************************************************/
static void
@@ -148,7 +157,6 @@ static void _CallPythonObject(void *mem,
void **pArgs)
{
PyObject *result = NULL;
- PyObject **args = NULL;
Py_ssize_t i = 0, j = 0, nargs = 0;
PyObject *error_object = NULL;
int *space;
@@ -156,24 +164,10 @@ static void _CallPythonObject(void *mem,
assert(PyTuple_Check(converters));
nargs = PyTuple_GET_SIZE(converters);
- /* Hm. What to return in case of error?
- For COM, 0xFFFFFFFF seems better than 0.
- */
- if (nargs < 0) {
- PrintError("BUG: PySequence_Length");
- goto Done;
- }
-
- PyObject *args_stack[CTYPES_MAX_ARGCOUNT];
- if (nargs <= CTYPES_MAX_ARGCOUNT) {
- args = args_stack;
- }
- else {
- args = PyMem_Malloc(nargs * sizeof(PyObject *));
- if (args == NULL) {
- PyErr_NoMemory();
- goto Done;
- }
+ assert(nargs <= CTYPES_MAX_ARGCOUNT);
+ PyObject **args = NULL;
+ if (nargs > 0) {
+ args = alloca(nargs * sizeof(PyObject *));
}
PyObject **cnvs = PySequence_Fast_ITEMS(converters);
@@ -310,9 +304,6 @@ static void _CallPythonObject(void *mem,
for (j = 0; j < i; j++) {
Py_DECREF(args[j]);
}
- if (args != args_stack) {
- PyMem_Free(args);
- }
PyGILState_Release(state);
}
diff --git a/Modules/_ctypes/callproc.c b/Modules/_ctypes/callproc.c
index 6dba0ffaa5159..4a6b8ec3ee016 100644
--- a/Modules/_ctypes/callproc.c
+++ b/Modules/_ctypes/callproc.c
@@ -1162,11 +1162,7 @@ PyObject *_ctypes_callproc(PPROC pProc,
return NULL;
}
- args = (struct argument *)alloca(sizeof(struct argument) * argcount);
- if (!args) {
- PyErr_NoMemory();
- return NULL;
- }
+ args = alloca(sizeof(struct argument) * argcount);
memset(args, 0, sizeof(struct argument) * argcount);
argtype_count = argtypes ? PyTuple_GET_SIZE(argtypes) : 0;
#ifdef MS_WIN32
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