gh-111903: Add `@critical_section` directive to Argument Clinic. (#111904)

The `@critical_section` directive instructs Argument Clinic to generate calls
to `Py_BEGIN_CRITICAL_SECTION()` and `Py_END_CRITICAL_SECTION()` around the
bound function. In `--disable-gil` builds, these calls will lock and unlock
the `self` object. They are no-ops in the default build.

This is used in one place (`_io._Buffered.close`) as a demonstration.
Subsequent PRs will use it more widely in the `_io.Buffered` bindings.

2 files changed, 11 insertions, 3 deletions

diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index e8caf9f..169b2b3 100644
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -10,6 +10,7 @@
 #include "Python.h"
 #include "pycore_bytesobject.h"   // _PyBytes_Join()
 #include "pycore_call.h"          // _PyObject_CallNoArgs()
+#include "pycore_critical_section.h"  // Py_BEGIN_CRITICAL_SECTION()
 #include "pycore_object.h"        // _PyObject_GC_UNTRACK()
 #include "pycore_pyerrors.h"      // _Py_FatalErrorFormat()
 #include "pycore_pylifecycle.h"   // _Py_IsInterpreterFinalizing()
@@ -521,12 +522,13 @@ buffered_closed_get(buffered *self, void *context)
 }
 
 /*[clinic input]
+@critical_section
 _io._Buffered.close
 [clinic start generated code]*/
 
 static PyObject *
 _io__Buffered_close_impl(buffered *self)
-/*[clinic end generated code: output=7280b7b42033be0c input=d20b83d1ddd7d805]*/
+/*[clinic end generated code: output=7280b7b42033be0c input=56d95935b03fd326]*/
 {
     PyObject *res = NULL;
     int r;
diff --git a/Modules/_io/clinic/bufferedio.c.h b/Modules/_io/clinic/bufferedio.c.h
index f6ac269..3fe0350 100644
--- a/Modules/_io/clinic/bufferedio.c.h
+++ b/Modules/_io/clinic/bufferedio.c.h
@@ -324,7 +324,13 @@ _io__Buffered_close_impl(buffered *self);
 static PyObject *
 _io__Buffered_close(buffered *self, PyObject *Py_UNUSED(ignored))
 {
-    return _io__Buffered_close_impl(self);
+    PyObject *return_value = NULL;
+
+    Py_BEGIN_CRITICAL_SECTION(self);
+    return_value = _io__Buffered_close_impl(self);
+    Py_END_CRITICAL_SECTION();
+
+    return return_value;
 }
 
 PyDoc_STRVAR(_io__Buffered_detach__doc__,
@@ -1075,4 +1081,4 @@ skip_optional_pos:
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=090e70253e35fc22 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=b23847480eba3d9b input=a9049054013a1b77]*/