[3.11] gh-95174: Add pthread stubs for WASI (GH-95234) (#95503)

Co-authored-by: Brett Cannon <brett@python.org>.
(cherry picked from commit 0fe645d6fd)

Co-authored-by: Christian Heimes <christian@python.org>

Python/thread.c

@@ -93,8 +93,15 @@ _PyThread_debug_deprecation(void)
 #endif
 }
 
-#if defined(_POSIX_THREADS)
-#   define PYTHREAD_NAME "pthread"
+#if defined(HAVE_PTHREAD_STUBS)
+#   define PYTHREAD_NAME "pthread-stubs"
+#   include "thread_pthread_stubs.h"
+#elif defined(_POSIX_THREADS)
+#   if defined(__EMSCRIPTEN__) || !defined(__EMSCRIPTEN_PTHREADS__)
+#     define PYTHREAD_NAME "pthread-stubs"
+#   else
+#     define PYTHREAD_NAME "pthread"
+#   endif
 #   include "thread_pthread.h"
 #elif defined(NT_THREADS)
 #   define PYTHREAD_NAME "nt"
@@ -208,7 +215,9 @@ PyThread_GetInfo(void)
     }
     PyStructSequence_SET_ITEM(threadinfo, pos++, value);
 
-#ifdef _POSIX_THREADS
+#ifdef HAVE_PTHREAD_STUBS
+    value = Py_NewRef(Py_None);
+#elif defined(_POSIX_THREADS)
 #ifdef USE_SEMAPHORES
     value = PyUnicode_FromString("semaphore");
 #else
@@ -219,8 +228,7 @@ PyThread_GetInfo(void)
         return NULL;
     }
 #else
-    Py_INCREF(Py_None);
-    value = Py_None;
+    value = Py_NewRef(Py_None);
 #endif
     PyStructSequence_SET_ITEM(threadinfo, pos++, value);
 

Python/thread_pthread.h

@@ -7,7 +7,9 @@
 #if defined(__APPLE__) || defined(HAVE_PTHREAD_DESTRUCTOR)
 #define destructor xxdestructor
 #endif
-#include <pthread.h>
+#ifndef HAVE_PTHREAD_STUBS
+#  include <pthread.h>
+#endif
 #if defined(__APPLE__) || defined(HAVE_PTHREAD_DESTRUCTOR)
 #undef destructor
 #endif

Python/thread_pthread_stubs.h

@@ -0,0 +1,185 @@
+#include "cpython/pthread_stubs.h"
+
+// mutex
+int
+pthread_mutex_init(pthread_mutex_t *restrict mutex,
+                   const pthread_mutexattr_t *restrict attr)
+{
+    return 0;
+}
+
+int
+pthread_mutex_destroy(pthread_mutex_t *mutex)
+{
+    return 0;
+}
+
+int
+pthread_mutex_trylock(pthread_mutex_t *mutex)
+{
+    return 0;
+}
+
+int
+pthread_mutex_lock(pthread_mutex_t *mutex)
+{
+    return 0;
+}
+
+int
+pthread_mutex_unlock(pthread_mutex_t *mutex)
+{
+    return 0;
+}
+
+// condition
+int
+pthread_cond_init(pthread_cond_t *restrict cond,
+                  const pthread_condattr_t *restrict attr)
+{
+    return 0;
+}
+
+PyAPI_FUNC(int)pthread_cond_destroy(pthread_cond_t *cond)
+{
+    return 0;
+}
+
+int
+pthread_cond_wait(pthread_cond_t *restrict cond,
+                  pthread_mutex_t *restrict mutex)
+{
+    return 0;
+}
+
+int
+pthread_cond_timedwait(pthread_cond_t *restrict cond,
+                       pthread_mutex_t *restrict mutex,
+                       const struct timespec *restrict abstime)
+{
+    return 0;
+}
+
+int
+pthread_cond_signal(pthread_cond_t *cond)
+{
+    return 0;
+}
+
+int
+pthread_condattr_init(pthread_condattr_t *attr)
+{
+    return 0;
+}
+
+int
+pthread_condattr_setclock(pthread_condattr_t *attr, clockid_t clock_id)
+{
+    return 0;
+}
+
+// pthread
+int
+pthread_create(pthread_t *restrict thread,
+               const pthread_attr_t *restrict attr,
+               void *(*start_routine)(void *),
+               void *restrict arg)
+{
+    return EAGAIN;
+}
+
+int
+pthread_detach(pthread_t thread)
+{
+    return 0;
+}
+
+PyAPI_FUNC(pthread_t) pthread_self(void)
+{
+    return 0;
+}
+
+int
+pthread_exit(void *retval)
+{
+    exit(0);
+}
+
+int
+pthread_attr_init(pthread_attr_t *attr)
+{
+    return 0;
+}
+
+int
+pthread_attr_setstacksize(
+    pthread_attr_t *attr, size_t stacksize)
+{
+    return 0;
+}
+
+int
+pthread_attr_destroy(pthread_attr_t *attr)
+{
+    return 0;
+}
+
+// pthread_key
+typedef struct {
+    bool in_use;
+    void *value;
+} py_tls_entry;
+
+static py_tls_entry py_tls_entries[PTHREAD_KEYS_MAX] = {0};
+
+int
+pthread_key_create(pthread_key_t *key, void (*destr_function)(void *))
+{
+    if (!key) {
+        return EINVAL;
+    }
+    if (destr_function != NULL) {
+        Py_FatalError("pthread_key_create destructor is not supported");
+    }
+    for (pthread_key_t idx = 0; idx < PTHREAD_KEYS_MAX; idx++) {
+        if (!py_tls_entries[idx].in_use) {
+            py_tls_entries[idx].in_use = true;
+            *key = idx;
+            return 0;
+        }
+    }
+    return EAGAIN;
+}
+
+int
+pthread_key_delete(pthread_key_t key)
+{
+    if (key < 0 || key >= PTHREAD_KEYS_MAX || !py_tls_entries[key].in_use) {
+        return EINVAL;
+    }
+    py_tls_entries[key].in_use = false;
+    py_tls_entries[key].value = NULL;
+    return 0;
+}
+
+
+void *
+pthread_getspecific(pthread_key_t key) {
+    if (key < 0 || key >= PTHREAD_KEYS_MAX || !py_tls_entries[key].in_use) {
+        return NULL;
+    }
+    return py_tls_entries[key].value;
+}
+
+int
+pthread_setspecific(pthread_key_t key, const void *value)
+{
+    if (key < 0 || key >= PTHREAD_KEYS_MAX || !py_tls_entries[key].in_use) {
+        return EINVAL;
+    }
+    py_tls_entries[key].value = (void *)value;
+    return 0;
+}
+
+// let thread_pthread define the Python API
+#include "thread_pthread.h"