Make _PyInterpreterConfig._isolated_interpreter more granular.

Author: ericsnowcurrently

Include/cpython/initconfig.h

@@ -238,11 +238,14 @@ PyAPI_FUNC(PyStatus) PyConfig_SetWideStringList(PyConfig *config,
     Py_ssize_t length, wchar_t **items);
 
 typedef struct {
-    // If non-zero, disallow threads, subprocesses, and fork.
-    // Default: 0.
-    unsigned int _isolated_interpreter:1;
+    /* Allow forking the process. */
+    unsigned int allow_fork:1;
+    /* Allow creating subprocesses. */
+    unsigned int allow_subprocess:1;
+    /* Allow the creation of threads. */
+    unsigned int allow_threading:1;
     /* Padding to ensure byte alignment. */
-    unsigned int :7;
+    unsigned int :5;
 } _PyInterpreterConfig;
 
 /* --- Helper functions --------------------------------------- */

Include/internal/pycore_runtime_init.h

@@ -63,6 +63,11 @@ extern "C" {
             }, \
         }, \
         ._initial_thread = _PyThreadState_INIT, \
+        .config = { \
+            .allow_fork = 1, \
+            .allow_subprocess = 1, \
+            .allow_threading = 1, \
+        }, \
     }
 
 #define _PyThreadState_INIT \

Modules/_posixsubprocess.c

@@ -776,7 +776,7 @@ subprocess_fork_exec(PyObject *module, PyObject *args)
 
     PyInterpreterState *interp = PyInterpreterState_Get();
     const _PyInterpreterConfig *config = _PyInterpreterState_GetConfig(interp);
-    if (config->_isolated_interpreter) {
+    if (!config->allow_subprocess) {
         PyErr_SetString(PyExc_RuntimeError,
                         "subprocess not supported for isolated subinterpreters");
         return NULL;

Modules/_threadmodule.c

@@ -1126,7 +1126,7 @@ thread_PyThread_start_new_thread(PyObject *self, PyObject *fargs)
     }
 
     PyInterpreterState *interp = _PyInterpreterState_GET();
-    if (_PyInterpreterState_GetConfig(interp)->_isolated_interpreter) {
+    if (!_PyInterpreterState_GetConfig(interp)->allow_threading) {
         PyErr_SetString(PyExc_RuntimeError,
                         "thread is not supported for isolated subinterpreters");
         return NULL;

Modules/_winapi.c

@@ -1091,7 +1091,7 @@ _winapi_CreateProcess_impl(PyObject *module,
 
     PyInterpreterState *interp = PyInterpreterState_Get();
     const _PyInterpreterConfig *config = _PyInterpreterState_GetConfig(interp);
-    if (config->_isolated_interpreter) {
+    if (!config->allow_subprocess) {
         PyErr_SetString(PyExc_RuntimeError,
                         "subprocess not supported for isolated subinterpreters");
         return NULL;

Modules/gcmodule.c

@@ -1197,7 +1197,7 @@ gc_collect_main(PyThreadState *tstate, int generation,
 
 #ifdef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
     PyInterpreterState *interp = tstate->interp;
-    if (_PyInterpreterState_GetConfig(interp)->_isolated_interpreter) {
+    if (!_PyInterpreterState_GetConfig(interp)->allow_threading) {
         // bpo-40533: The garbage collector must not be run on parallel on
         // Python objects shared by multiple interpreters.
         return 0;

Modules/posixmodule.c

@@ -6780,7 +6780,7 @@ os_fork_impl(PyObject *module)
 {
     pid_t pid;
     PyInterpreterState *interp = _PyInterpreterState_GET();
-    if (_PyInterpreterState_GetConfig(interp)->_isolated_interpreter) {
+    if (!_PyInterpreterState_GetConfig(interp)->allow_fork) {
         PyErr_SetString(PyExc_RuntimeError,
                         "fork not supported for isolated subinterpreters");
         return NULL;

Python/initconfig.c

@@ -3029,7 +3029,9 @@ _Py_DumpPathConfig(PyThreadState *tstate)
 void
 _PyInterpreterConfig_Clear(_PyInterpreterConfig *config)
 {
-    config->_isolated_interpreter = 0;
+    config->allow_fork = 0;
+    config->allow_subprocess = 0;
+    config->allow_threading = 0;
 }
 
 
@@ -3041,7 +3043,9 @@ _PyInterpreterConfig_Copy(_PyInterpreterConfig *config,
 
 #define COPY_ATTR(ATTR) config->ATTR = config2->ATTR
 
-    COPY_ATTR(_isolated_interpreter);
+    COPY_ATTR(allow_fork);
+    COPY_ATTR(allow_subprocess);
+    COPY_ATTR(allow_threading);
 
 #undef COPY_ATTR