bpo-25658: Implement PEP 539 for Thread Specific Storage (TSS) API (GH-1362)

See PEP 539 for details.

Highlights of changes:

- Add Thread Specific Storage (TSS) API
- Document the Thread Local Storage (TLS) API as deprecated
- Update code that used TLS API to use TSS API

1 files changed, 87 insertions, 3 deletions

diff --git a/Python/thread_pthread.h b/Python/thread_pthread.h
index 2dcd107..c5b7f32 100644
--- a/Python/thread_pthread.h
+++ b/Python/thread_pthread.h
@@ -589,9 +589,25 @@ _pythread_pthread_set_stacksize(size_t size)
 #define THREAD_SET_STACKSIZE(x) _pythread_pthread_set_stacksize(x)
 
 
+/* Thread Local Storage (TLS) API
+
+   This API is DEPRECATED since Python 3.7.  See PEP 539 for details.
+*/
+
+/* Issue #25658: On platforms where native TLS key is defined in a way that
+   cannot be safely cast to int, PyThread_create_key returns immediately a
+   failure status and other TLS functions all are no-ops.  This indicates
+   clearly that the old API is not supported on platforms where it cannot be
+   used reliably, and that no effort will be made to add such support.
+
+   Note: PTHREAD_KEY_T_IS_COMPATIBLE_WITH_INT will be unnecessary after
+   removing this API.
+*/
+
 int
 PyThread_create_key(void)
 {
+#ifdef PTHREAD_KEY_T_IS_COMPATIBLE_WITH_INT
     pthread_key_t key;
     int fail = pthread_key_create(&key, NULL);
     if (fail)
@@ -603,34 +619,102 @@ PyThread_create_key(void)
         return -1;
     }
     return (int)key;
+#else
+    return -1;  /* never return valid key value. */
+#endif
 }
 
 void
 PyThread_delete_key(int key)
 {
+#ifdef PTHREAD_KEY_T_IS_COMPATIBLE_WITH_INT
     pthread_key_delete(key);
+#endif
 }
 
 void
 PyThread_delete_key_value(int key)
 {
+#ifdef PTHREAD_KEY_T_IS_COMPATIBLE_WITH_INT
     pthread_setspecific(key, NULL);
+#endif
 }
 
 int
 PyThread_set_key_value(int key, void *value)
 {
-    int fail;
-    fail = pthread_setspecific(key, value);
+#ifdef PTHREAD_KEY_T_IS_COMPATIBLE_WITH_INT
+    int fail = pthread_setspecific(key, value);
     return fail ? -1 : 0;
+#else
+    return -1;
+#endif
 }
 
 void *
 PyThread_get_key_value(int key)
 {
+#ifdef PTHREAD_KEY_T_IS_COMPATIBLE_WITH_INT
     return pthread_getspecific(key);
+#else
+    return NULL;
+#endif
 }
 
+
 void
 PyThread_ReInitTLS(void)
-{}
+{
+}
+
+
+/* Thread Specific Storage (TSS) API
+
+   Platform-specific components of TSS API implementation.
+*/
+
+int
+PyThread_tss_create(Py_tss_t *key)
+{
+    assert(key != NULL);
+    /* If the key has been created, function is silently skipped. */
+    if (key->_is_initialized) {
+        return 0;
+    }
+
+    int fail = pthread_key_create(&(key->_key), NULL);
+    if (fail) {
+        return -1;
+    }
+    key->_is_initialized = 1;
+    return 0;
+}
+
+void
+PyThread_tss_delete(Py_tss_t *key)
+{
+    assert(key != NULL);
+    /* If the key has not been created, function is silently skipped. */
+    if (!key->_is_initialized) {
+        return;
+    }
+
+    pthread_key_delete(key->_key);
+    /* pthread has not provided the defined invalid value for the key. */
+    key->_is_initialized = 0;
+}
+
+int
+PyThread_tss_set(Py_tss_t *key, void *value)
+{
+    assert(key != NULL);
+    int fail = pthread_setspecific(key->_key, value);
+    return fail ? -1 : 0;
+}
+
+void *
+PyThread_tss_get(Py_tss_t *key)
+{
+    assert(key != NULL);
+    return pthread_getspecific(key->_key);
+}