gh-101659: Add _Py_AtExit() (gh-103298)

The function is like Py_AtExit() but for a single interpreter.  This is a companion to the atexit module's register() function, taking a C callback instead of a Python one.

We also update the _xxinterpchannels module to use _Py_AtExit(), which is the motivating case.  (This is inspired by pain points felt while working on gh-101660.)

3 files changed, 60 insertions, 18 deletions

diff --git a/Include/internal/pycore_atexit.h b/Include/internal/pycore_atexit.h
new file mode 100644
index 0000000..b4663b3
--- /dev/null
+++ b/Include/internal/pycore_atexit.h
@@ -0,0 +1,56 @@
+#ifndef Py_INTERNAL_ATEXIT_H
+#define Py_INTERNAL_ATEXIT_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
+
+//###############
+// runtime atexit
+
+typedef void (*atexit_callbackfunc)(void);
+
+struct _atexit_runtime_state {
+#define NEXITFUNCS 32
+    atexit_callbackfunc callbacks[NEXITFUNCS];
+    int ncallbacks;
+};
+
+
+//###################
+// interpreter atexit
+
+struct atexit_callback;
+typedef struct atexit_callback {
+    atexit_datacallbackfunc func;
+    void *data;
+    struct atexit_callback *next;
+} atexit_callback;
+
+typedef struct {
+    PyObject *func;
+    PyObject *args;
+    PyObject *kwargs;
+} atexit_py_callback;
+
+struct atexit_state {
+    atexit_callback *ll_callbacks;
+    atexit_callback *last_ll_callback;
+
+    // XXX The rest of the state could be moved to the atexit module state
+    // and a low-level callback added for it during module exec.
+    // For the moment we leave it here.
+    atexit_py_callback **callbacks;
+    int ncallbacks;
+    int callback_len;
+};
+
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_INTERNAL_ATEXIT_H */
diff --git a/Include/internal/pycore_interp.h b/Include/internal/pycore_interp.h
index 1f2c0db..d64a68c 100644
--- a/Include/internal/pycore_interp.h
+++ b/Include/internal/pycore_interp.h
@@ -10,8 +10,9 @@ extern "C" {
 
 #include <stdbool.h>
 
-#include "pycore_atomic.h"        // _Py_atomic_address
 #include "pycore_ast_state.h"     // struct ast_state
+#include "pycore_atexit.h"        // struct atexit_state
+#include "pycore_atomic.h"        // _Py_atomic_address
 #include "pycore_ceval_state.h"   // struct _ceval_state
 #include "pycore_code.h"          // struct callable_cache
 #include "pycore_context.h"       // struct _Py_context_state
@@ -32,20 +33,6 @@ extern "C" {
 #include "pycore_warnings.h"      // struct _warnings_runtime_state
 
 
-// atexit state
-typedef struct {
-    PyObject *func;
-    PyObject *args;
-    PyObject *kwargs;
-} atexit_callback;
-
-struct atexit_state {
-    atexit_callback **callbacks;
-    int ncallbacks;
-    int callback_len;
-};
-
-
 struct _Py_long_state {
     int max_str_digits;
 };
diff --git a/Include/internal/pycore_runtime.h b/Include/internal/pycore_runtime.h
index 8877b28..3ebe499 100644
--- a/Include/internal/pycore_runtime.h
+++ b/Include/internal/pycore_runtime.h
@@ -8,6 +8,7 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
+#include "pycore_atexit.h"          // struct atexit_runtime_state
 #include "pycore_atomic.h"          /* _Py_atomic_address */
 #include "pycore_ceval_state.h"     // struct _ceval_runtime_state
 #include "pycore_floatobject.h"     // struct _Py_float_runtime_state
@@ -131,9 +132,7 @@ typedef struct pyruntimestate {
 
     struct _parser_runtime_state parser;
 
-#define NEXITFUNCS 32
-    void (*exitfuncs[NEXITFUNCS])(void);
-    int nexitfuncs;
+    struct _atexit_runtime_state atexit;
 
     struct _import_runtime_state imports;
     struct _ceval_runtime_state ceval;