PyUnstable_ThreadState_SetStack() can fail

Author: vstinner

Doc/c-api/init.rst

@@ -1353,12 +1353,15 @@ All of the following functions must be called after :c:func:`Py_Initialize`.
    .. versionadded:: 3.11
 
 
-.. c:function:: void PyUnstable_ThreadState_SetStack(PyThreadState *tstate, void *stack_start_addr, size_t stack_size)
+.. c:function:: int PyUnstable_ThreadState_SetStack(PyThreadState *tstate, void *stack_start_addr, size_t stack_size)
 
    Set the stack start address and stack size of a Python thread state.
 
    *stack_size* must be greater than ``0``.
 
+   On success, return ``0``.
+   On failure, set an exception and return ``-1``.
+
    .. seealso::
       The :c:func:`PyUnstable_ThreadState_ResetStack` function.
 

Include/cpython/pystate.h

@@ -253,7 +253,7 @@ PyAPI_FUNC(int) PyGILState_Check(void);
 PyAPI_FUNC(PyObject*) _PyThread_CurrentFrames(void);
 
 // Set the stack start address and stack size of a Python thread state
-PyAPI_FUNC(void) PyUnstable_ThreadState_SetStack(
+PyAPI_FUNC(int) PyUnstable_ThreadState_SetStack(
     PyThreadState *tstate,
     void *stack_start_addr,  // Stack start address
     size_t stack_size);      // Stack size (in bytes)

Modules/_testinternalcapi.c

@@ -2421,7 +2421,8 @@ set_vectorcall_nop(PyObject *self, PyObject *func)
 static void
 check_threadstate_set_stack(PyThreadState *tstate, void *start, size_t size)
 {
-    PyUnstable_ThreadState_SetStack(tstate, start, size);
+    assert(PyUnstable_ThreadState_SetStack(tstate, start, size) == 0);
+    assert(!PyErr_Occurred());
 
     _PyThreadStateImpl *ts = (_PyThreadStateImpl *)tstate;
     assert(ts->c_stack_hard_limit == (uintptr_t)start);
@@ -2435,6 +2436,7 @@ static PyObject *
 test_threadstate_set_stack(PyObject *self, PyObject *Py_UNUSED(args))
 {
     PyThreadState *tstate = PyThreadState_GET();
+    assert(!PyErr_Occurred());
 
     // Test a size smaller than _PyOS_STACK_MARGIN_BYTES
     size_t size = 4096;

Python/ceval.c

@@ -440,8 +440,8 @@ int pthread_attr_destroy(pthread_attr_t *a)
 
 
 void
-PyUnstable_ThreadState_SetStack(PyThreadState *tstate,
-    void *stack_start_addr, size_t stack_size)
+tstate_set_stack(PyThreadState *tstate,
+                 void *stack_start_addr, size_t stack_size)
 {
     assert(stack_size > 0);
 
@@ -473,6 +473,21 @@ PyUnstable_ThreadState_SetStack(PyThreadState *tstate,
 }
 
 
+int
+PyUnstable_ThreadState_SetStack(PyThreadState *tstate,
+                                void *stack_start_addr, size_t stack_size)
+{
+    if (stack_size == 0) {
+        PyErr_SetString(PyExc_ValueError, "stack_size must be greater than 0");
+        return -1;
+    }
+
+    tstate_set_stack(tstate, stack_start_addr, stack_size);
+    return 0;
+}
+
+
+
 void
 PyUnstable_ThreadState_ResetStack(PyThreadState *tstate)
 {
@@ -485,13 +500,13 @@ PyUnstable_ThreadState_ResetStack(PyThreadState *tstate)
 
     uintptr_t start = (uintptr_t)low + guarantee + _PyOS_STACK_MARGIN_BYTES;
     size_t size = (uintptr_t)high - start;
-    PyUnstable_ThreadState_SetStack(tstate, (void*)start, size);
+    tstate_set_stack(tstate, (void*)start, size);
 
 #elif defined(__APPLE__)
     pthread_t this_thread = pthread_self();
     void *top = pthread_get_stackaddr_np(this_thread); // top of the stack
     size_t size = pthread_get_stacksize_np(this_thread);
-    PyUnstable_ThreadState_SetStack(tstate, (char*)top - size, size);
+    tstate_set_stack(tstate, (char*)top - size, size);
 
 #else
    // XXX musl supports HAVE_PTHRED_GETATTR_NP, but the resulting stack size
@@ -512,7 +527,7 @@ PyUnstable_ThreadState_ResetStack(PyThreadState *tstate)
         uintptr_t base = ((uintptr_t)stack_addr) + guard_size;
         uintptr_t start = base + _PyOS_STACK_MARGIN_BYTES;
         size_t pystack_size = (base + stack_size) - start;
-        PyUnstable_ThreadState_SetStack(tstate, (void*)start, pystack_size);
+        tstate_set_stack(tstate, (void*)start, pystack_size);
     }
     else
 #  endif
@@ -521,7 +536,7 @@ PyUnstable_ThreadState_ResetStack(PyThreadState *tstate)
         uintptr_t top = _Py_SIZE_ROUND_UP(here_addr, 4096);
         uintptr_t start = top - (Py_C_STACK_SIZE + _PyOS_STACK_MARGIN_BYTES);
         size_t pystack_size = top - start;
-        PyUnstable_ThreadState_SetStack(tstate, (void*)start, pystack_size);
+        tstate_set_stack(tstate, (void*)start, pystack_size);
     }
 #endif
 }