gh-95174: Add pthread stubs for WASI (GH-95234)

Co-authored-by: Brett Cannon <brett@python.org>

2 files changed, 91 insertions, 0 deletions

diff --git a/Include/cpython/pthread_stubs.h b/Include/cpython/pthread_stubs.h
new file mode 100644
index 0000000..d95ee03
--- /dev/null
+++ b/Include/cpython/pthread_stubs.h
@@ -0,0 +1,88 @@
+#ifndef Py_CPYTHON_PTRHEAD_STUBS_H
+#define Py_CPYTHON_PTRHEAD_STUBS_H
+
+#if !defined(HAVE_PTHREAD_STUBS)
+#  error "this header file requires stubbed pthreads."
+#endif
+
+#ifndef _POSIX_THREADS
+#  define _POSIX_THREADS 1
+#endif
+
+/* Minimal pthread stubs for CPython.
+ *
+ * The stubs implement the minimum pthread API for CPython.
+ * - pthread_create() fails.
+ * - pthread_exit() calls exit(0).
+ * - pthread_key_*() functions implement minimal TSS without destructor.
+ * - all other functions do nothing and return 0.
+ */
+
+#ifdef __wasi__
+// WASI's bits/alltypes.h provides type definitions when __NEED_ is set.
+// The header file can be included multiple times.
+#  define __NEED_pthread_cond_t 1
+#  define __NEED_pthread_condattr_t 1
+#  define __NEED_pthread_mutex_t 1
+#  define __NEED_pthread_mutexattr_t 1
+#  define __NEED_pthread_key_t 1
+#  define __NEED_pthread_t 1
+#  define __NEED_pthread_attr_t 1
+#  include <bits/alltypes.h>
+#else
+typedef struct { void *__x; } pthread_cond_t;
+typedef struct { unsigned __attr; } pthread_condattr_t;
+typedef struct { void *__x; } pthread_mutex_t;
+typedef struct { unsigned __attr; } pthread_mutexattr_t;
+typedef unsigned pthread_key_t;
+typedef unsigned pthread_t;
+typedef struct { unsigned __attr; } pthread_attr_t;
+#endif
+
+// mutex
+PyAPI_FUNC(int) pthread_mutex_init(pthread_mutex_t *restrict mutex,
+                                   const pthread_mutexattr_t *restrict attr);
+PyAPI_FUNC(int) pthread_mutex_destroy(pthread_mutex_t *mutex);
+PyAPI_FUNC(int) pthread_mutex_trylock(pthread_mutex_t *mutex);
+PyAPI_FUNC(int) pthread_mutex_lock(pthread_mutex_t *mutex);
+PyAPI_FUNC(int) pthread_mutex_unlock(pthread_mutex_t *mutex);
+
+// condition
+PyAPI_FUNC(int) pthread_cond_init(pthread_cond_t *restrict cond,
+                                  const pthread_condattr_t *restrict attr);
+PyAPI_FUNC(int) pthread_cond_destroy(pthread_cond_t *cond);
+PyAPI_FUNC(int) pthread_cond_wait(pthread_cond_t *restrict cond,
+                                  pthread_mutex_t *restrict mutex);
+PyAPI_FUNC(int) pthread_cond_timedwait(pthread_cond_t *restrict cond,
+                                       pthread_mutex_t *restrict mutex,
+                                       const struct timespec *restrict abstime);
+PyAPI_FUNC(int) pthread_cond_signal(pthread_cond_t *cond);
+PyAPI_FUNC(int) pthread_condattr_init(pthread_condattr_t *attr);
+PyAPI_FUNC(int) pthread_condattr_setclock(
+    pthread_condattr_t *attr, clockid_t clock_id);
+
+// pthread
+PyAPI_FUNC(int) pthread_create(pthread_t *restrict thread,
+                               const pthread_attr_t *restrict attr,
+                               void *(*start_routine)(void *),
+                               void *restrict arg);
+PyAPI_FUNC(int) pthread_detach(pthread_t thread);
+PyAPI_FUNC(pthread_t) pthread_self(void);
+PyAPI_FUNC(int) pthread_exit(void *retval) __attribute__ ((__noreturn__));
+PyAPI_FUNC(int) pthread_attr_init(pthread_attr_t *attr);
+PyAPI_FUNC(int) pthread_attr_setstacksize(pthread_attr_t *attr, size_t stacksize);
+PyAPI_FUNC(int) pthread_attr_destroy(pthread_attr_t *attr);
+
+
+// pthread_key
+#ifndef PTHREAD_KEYS_MAX
+#  define PTHREAD_KEYS_MAX 128
+#endif
+
+PyAPI_FUNC(int) pthread_key_create(pthread_key_t *key,
+                                   void (*destr_function)(void *));
+PyAPI_FUNC(int) pthread_key_delete(pthread_key_t key);
+PyAPI_FUNC(void *) pthread_getspecific(pthread_key_t key);
+PyAPI_FUNC(int) pthread_setspecific(pthread_key_t key, const void *value);
+
+#endif // Py_CPYTHON_PTRHEAD_STUBS_H
diff --git a/Include/cpython/pythread.h b/Include/cpython/pythread.h
index 1fd86a6..ce4ec8f 100644
--- a/Include/cpython/pythread.h
+++ b/Include/cpython/pythread.h
@@ -20,6 +20,9 @@ PyAPI_FUNC(int) _PyThread_at_fork_reinit(PyThread_type_lock *lock);
        but hardcode the unsigned long to avoid errors for include directive.
     */
 #   define NATIVE_TSS_KEY_T     unsigned long
+#elif defined(HAVE_PTHREAD_STUBS)
+#   include "cpython/pthread_stubs.h"
+#   define NATIVE_TSS_KEY_T     pthread_key_t
 #else
 #   error "Require native threads. See https://bugs.python.org/issue31370"
 #endif