bpo-37146: Deactivate opcode cache only when using huntrleaks in the test suite (GH-24643)

Author: pablogsal

Include/cpython/ceval.h

@@ -28,3 +28,5 @@ PyAPI_FUNC(Py_ssize_t) _PyEval_RequestCodeExtraIndex(freefunc);
 
 PyAPI_FUNC(int) _PyEval_SliceIndex(PyObject *, Py_ssize_t *);
 PyAPI_FUNC(int) _PyEval_SliceIndexNotNone(PyObject *, Py_ssize_t *);
+
+PyAPI_FUNC(void) _PyEval_DeactivateOpCache(void);

Lib/test/libregrtest/setup.py

@@ -62,6 +62,7 @@ def setup_tests(ns):
 
     if ns.huntrleaks:
         unittest.BaseTestSuite._cleanup = False
+        sys._deactivate_opcache()
 
     if ns.memlimit is not None:
         support.set_memlimit(ns.memlimit)

Python/ceval.c

@@ -107,17 +107,19 @@ static long dxp[256];
 #endif
 
 /* per opcode cache */
-#ifdef Py_DEBUG
-// --with-pydebug is used to find memory leak.  opcache makes it harder.
-// So we disable opcache when Py_DEBUG is defined.
-// See bpo-37146
-#define OPCACHE_MIN_RUNS 0  /* disable opcache */
-#else
-#define OPCACHE_MIN_RUNS 1024  /* create opcache when code executed this time */
-#endif
+static int opcache_min_runs = 1024;  /* create opcache when code executed this many times */
 #define OPCODE_CACHE_MAX_TRIES 20
 #define OPCACHE_STATS 0  /* Enable stats */
 
+// This function allows to deactivate the opcode cache. As different cache mechanisms may hold
+// references, this can mess with the reference leak detector functionality so the cache needs
+// to be deactivated in such scenarios to avoid false positives. See bpo-3714 for more information.
+void
+_PyEval_DeactivateOpCache(void)
+{
+    opcache_min_runs = 0;
+}
+
 #if OPCACHE_STATS
 static size_t opcache_code_objects = 0;
 static size_t opcache_code_objects_extra_mem = 0;
@@ -1705,9 +1707,9 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, PyFrameObject *f, int throwflag)
     f->f_stackdepth = -1;
     f->f_state = FRAME_EXECUTING;
 
-    if (co->co_opcache_flag < OPCACHE_MIN_RUNS) {
+    if (co->co_opcache_flag < opcache_min_runs) {
         co->co_opcache_flag++;
-        if (co->co_opcache_flag == OPCACHE_MIN_RUNS) {
+        if (co->co_opcache_flag == opcache_min_runs) {
             if (_PyCode_InitOpcache(co) < 0) {
                 goto exit_eval_frame;
             }

Python/clinic/sysmodule.c.h

@@ -1958,6 +1958,20 @@ sys_getandroidapilevel_impl(PyObject *module)
 #endif   /* ANDROID_API_LEVEL */
 
 
+/*[clinic input]
+sys._deactivate_opcache
+
+Deactivate the opcode cache permanently
+[clinic start generated code]*/
+
+static PyObject *
+sys__deactivate_opcache_impl(PyObject *module)
+/*[clinic end generated code: output=00e20982bd012122 input=501eac146735ccf9]*/
+{
+    _PyEval_DeactivateOpCache();
+    Py_RETURN_NONE;
+}
+
 
 static PyMethodDef sys_methods[] = {
     /* Might as well keep this in alphabetic order */
@@ -2011,6 +2025,7 @@ static PyMethodDef sys_methods[] = {
     SYS_GET_ASYNCGEN_HOOKS_METHODDEF
     SYS_GETANDROIDAPILEVEL_METHODDEF
     SYS_UNRAISABLEHOOK_METHODDEF
+    SYS__DEACTIVATE_OPCACHE_METHODDEF
     {NULL,              NULL}           /* sentinel */
 };