bpo-38644: Add Py_EnterRecursiveCall() to the limited API (GH-17046)

Provide Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() as
regular functions for the limited API. Previously, there were defined
as macros, but these macros didn't work with the limited API which
cannot access PyThreadState.recursion_depth field.

Remove _Py_CheckRecursionLimit from the stable ABI.

Add Include/cpython/ceval.h header file.

1 files changed, 50 insertions, 0 deletions

diff --git a/Include/cpython/ceval.h b/Include/cpython/ceval.h
new file mode 100644
index 0000000..61bbc4f
--- /dev/null
+++ b/Include/cpython/ceval.h
@@ -0,0 +1,50 @@
+#ifndef Py_CPYTHON_CEVAL_H
+#  error "this header file must not be included directly"
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+PyAPI_DATA(int) _Py_CheckRecursionLimit;
+
+#ifdef USE_STACKCHECK
+/* With USE_STACKCHECK macro defined, trigger stack checks in
+   _Py_CheckRecursiveCall() on every 64th call to Py_EnterRecursiveCall. */
+#  define _Py_MakeRecCheck(x)  \
+    (++(x) > _Py_CheckRecursionLimit || \
+     ++(PyThreadState_GET()->stackcheck_counter) > 64)
+#else
+#  define _Py_MakeRecCheck(x)  (++(x) > _Py_CheckRecursionLimit)
+#endif
+
+PyAPI_FUNC(int) _Py_CheckRecursiveCall(const char *where);
+
+#define _Py_EnterRecursiveCall_macro(where)  \
+            (_Py_MakeRecCheck(PyThreadState_GET()->recursion_depth) &&  \
+             _Py_CheckRecursiveCall(where))
+
+#define Py_EnterRecursiveCall(where) _Py_EnterRecursiveCall_macro(where)
+
+
+/* Compute the "lower-water mark" for a recursion limit. When
+ * Py_LeaveRecursiveCall() is called with a recursion depth below this mark,
+ * the overflowed flag is reset to 0. */
+#define _Py_RecursionLimitLowerWaterMark(limit) \
+    (((limit) > 200) \
+        ? ((limit) - 50) \
+        : (3 * ((limit) >> 2)))
+
+#define _Py_MakeEndRecCheck(x) \
+    (--(x) < _Py_RecursionLimitLowerWaterMark(_Py_CheckRecursionLimit))
+
+#define _Py_LeaveRecursiveCall_macro()                         \
+    do{ if(_Py_MakeEndRecCheck(PyThreadState_GET()->recursion_depth))  \
+      PyThreadState_GET()->overflowed = 0;  \
+    } while(0)
+
+#define Py_LeaveRecursiveCall() _Py_LeaveRecursiveCall_macro()
+
+#ifdef __cplusplus
+}
+#endif