Sep 15, 2023 · Jun 28, 2023 · Jun 29, 2023 · Jun 29, 2023 · Jun 29, 2023 · Jun 29, 2023
diff --git a/Include/internal/pycore_emscripten_trampoline.h b/Include/internal/pycore_emscripten_trampoline.h
 #ifndef Py_EMSCRIPTEN_TRAMPOLINE_H
 #define Py_EMSCRIPTEN_TRAMPOLINE_H


 /**
 * C function call trampolines to mitigate bad function pointer casts.
 *
 * Section 6.3.2.3, paragraph 8 reads:
 *
 *      A pointer to a function of one type may be converted to a pointer to a
 *      function of another type and back again; the result shall compare equal to
 *      the original pointer. If a converted pointer is used to call a function
 *      whose type is not compatible with the pointed-to type, the behavior is
 *      undefined.
 *
 * Typical native ABIs ignore additional arguments or fill in missing values
 * with 0/NULL in function pointer cast. Compilers do not show warnings when a
 * function pointer is explicitly casted to an incompatible type.
 *
 * Bad fpcasts are an issue in WebAssembly. WASM's indirect_call has strict
 * function signature checks. Argument count, types, and return type must match.
 *
 * Third party code unintentionally rely on problematic fpcasts. The call
 * trampoline mitigates common occurrences of bad fpcasts on Emscripten.
 */

 #if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)

 void _Py_EmscriptenTrampoline_Init(void);

 PyObject*
 _PyEM_TrampolineCall(PyCFunctionWithKeywords func,
                     PyObject* self,
                     PyObject* args,
                     PyObject* kw);

 #define _PyCFunction_TrampolineCall(meth, self, args) \
    _PyEM_TrampolineCall( \
        (*(PyCFunctionWithKeywords)(void(*)(void))(meth)), (self), (args), NULL)

 #define _PyCFunctionWithKeywords_TrampolineCall(meth, self, args, kw) \
    _PyEM_TrampolineCall((meth), (self), (args), (kw))

 #else // defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)

 #define _Py_EmscriptenTrampoline_Init()

 #define _PyCFunction_TrampolineCall(meth, self, args) \
    (meth)((self), (args))
 #define _PyCFunctionWithKeywords_TrampolineCall(meth, self, args, kw) \
    (meth)((self), (args), (kw))

 #endif // defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
 #endif // ndef Py_EMSCRIPTEN_SIGNAL_H
diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h

 #include <stdbool.h>
 #include "pycore_gc.h"            // _PyObject_GC_IS_TRACKED()
 #include "pycore_emscripten_trampoline.h" // _PyCFunction_TrampolineCall()
 #include "pycore_interp.h"        // PyInterpreterState.gc
 #include "pycore_pystate.h"       // _PyInterpreterState_GET()
 #include "pycore_runtime.h"       // _PyRuntime



 /* We need to maintain an internal copy of Py{Var}Object_HEAD_INIT to avoid
   designated initializer conflicts in C++20. If we use the deinition in
   object.h, we will be mixing designated and non-designated initializers in

 PyAPI_FUNC(PyObject *) _PyObject_LookupSpecial(PyObject *, PyObject *);

 /* C function call trampolines to mitigate bad function pointer casts.
 *
 * Typical native ABIs ignore additional arguments or fill in missing
 * values with 0/NULL in function pointer cast. Compilers do not show
 * warnings when a function pointer is explicitly casted to an
 * incompatible type.
 *
 * Bad fpcasts are an issue in WebAssembly. WASM's indirect_call has strict
 * function signature checks. Argument count, types, and return type must
 * match.
 *
 * Third party code unintentionally rely on problematic fpcasts. The call
 * trampoline mitigates common occurrences of bad fpcasts on Emscripten.
 */
 #if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
 #define _PyCFunction_TrampolineCall(meth, self, args) \
    _PyCFunctionWithKeywords_TrampolineCall( \
        (*(PyCFunctionWithKeywords)(void(*)(void))(meth)), (self), (args), NULL)
 extern PyObject* _PyCFunctionWithKeywords_TrampolineCall(
    PyCFunctionWithKeywords meth, PyObject *, PyObject *, PyObject *);
 #else
 #define _PyCFunction_TrampolineCall(meth, self, args) \
    (meth)((self), (args))
 #define _PyCFunctionWithKeywords_TrampolineCall(meth, self, args, kw) \
    (meth)((self), (args), (kw))
 #endif // __EMSCRIPTEN__ && PY_CALL_TRAMPOLINE

 #ifdef __cplusplus
 }
 #endif
diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-06-29-09-42-56.gh-issue-106213.TCUgzM.rst b/Misc/NEWS.d/next/Core and Builtins/2023-06-29-09-42-56.gh-issue-106213.TCUgzM.rst
 Changed the way that Emscripten call trampolines work for compatibility with
 Wasm/JS Promise integration.
diff --git a/Objects/descrobject.c b/Objects/descrobject.c

 // see pycore_object.h
 #if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
 #include <emscripten.h>
 EM_JS(int, descr_set_trampoline_call, (setter set, PyObject *obj, PyObject *value, void *closure), {
    return wasmTable.get(set)(obj, value, closure);
 });

 EM_JS(PyObject*, descr_get_trampoline_call, (getter get, PyObject *obj, void *closure), {
    return wasmTable.get(get)(obj, closure);
 });
 extern PyObject*
 _PyEM_TrampolineCall(PyCFunctionWithKeywords func,
                     PyObject* self,
                     PyObject* args,
                     PyObject* kw);

 #define descr_set_trampoline_call(set, obj, value, closure) \
    ((int)_PyEM_TrampolineCall((PyCFunctionWithKeywords)(set), (obj), (value), (PyObject*)(closure)))


 #define descr_get_trampoline_call(get, obj, closure) \
    _PyEM_TrampolineCall((PyCFunctionWithKeywords)(get), (obj), (PyObject*)(closure), NULL)

 #else

 #define descr_set_trampoline_call(set, obj, value, closure) \
    (set)((obj), (value), (closure))

diff --git a/Objects/methodobject.c b/Objects/methodobject.c
    return _Py_CheckFunctionResult(tstate, func, result, NULL);
 }

 #if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
 #include <emscripten.h>

 EM_JS(PyObject*, _PyCFunctionWithKeywords_TrampolineCall, (PyCFunctionWithKeywords func, PyObject *self, PyObject *args, PyObject *kw), {
    return wasmTable.get(func)(self, args, kw);
 });
 #endif
diff --git a/Python/emscripten_trampoline.c b/Python/emscripten_trampoline.c
 #if defined(PY_CALL_TRAMPOLINE)

 #include <emscripten.h>
 #include <Python.h>

 static int type_reflection_available;

 /**
 * This is the GoogleChromeLabs approved way to feature detect type-reflection:
 * https://github.com/GoogleChromeLabs/wasm-feature-detect/blob/main/src/detectors/type-reflection/index.js
 */
 EM_JS(int, _PyEM_detect_type_reflection, (), {
  return "function" in WebAssembly;
 });

 void
 _Py_EmscriptenTrampoline_Init(){
  type_reflection_available = _PyEM_detect_type_reflection();
 }

 /**
 * Backwards compatible trampoline works with all JS runtimes
 */
 EM_JS_DEPS(_PyEMJS_TrampolineCall, "$getWasmTableEntry")
 EM_JS(PyObject*, _PyEMJS_TrampolineCall, (PyCFunctionWithKeywords func, PyObject *arg1, PyObject *arg2, PyObject *arg3), {
    return getWasmTableEntry(func)(arg1, arg2, arg3);
 }
 );

 /**
 * In runtimes with WebAssembly type reflection, count the number of parameters
 * and cast to the appropriate signature
 */
 EM_JS(int, _PyEM_CountFuncParams, (PyCFunctionWithKeywords func), {
  let n = _PyEM_CountFuncParams.cache.get(func);
  if (n !== undefined) {
    return n;
  }
  n = WebAssembly.Function.type(getWasmTableEntry(func)).parameters.length;
  _PyEM_CountFuncParams.cache.set(func, n);
  return n;
 }
 _PyEM_CountFuncParams.cache = new Map();
 )


 typedef PyObject* (*zero_arg)(void);
 typedef PyObject* (*one_arg)(PyObject*);
 typedef PyObject* (*two_arg)(PyObject*, PyObject*);
 typedef PyObject* (*three_arg)(PyObject*, PyObject*, PyObject*);


 PyObject*
 _PyEM_TrampolineCall(PyCFunctionWithKeywords func,
              PyObject* self,
              PyObject* args,
              PyObject* kw)
 {
  if (!type_reflection_available) {
    return _PyEMJS_TrampolineCall(func, self, args, kw);
  } else {
    switch (_PyEM_CountFuncParams(func)) {
      case 0:
        return ((zero_arg)func)();
      case 1:
        return ((one_arg)func)(self);
      case 2:
        return ((two_arg)func)(self, args);
      case 3:
        return ((three_arg)func)(self, args, kw);
      default:
        PyErr_SetString(PyExc_SystemError, "Handler takes too many arguments");
        return NULL;
    }
  }
 }

 #endif
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
 #include "pycore_codecs.h"        // _PyCodec_Lookup()
 #include "pycore_context.h"       // _PyContext_Init()
 #include "pycore_dict.h"          // _PyDict_Fini()
 #include "pycore_emscripten_trampoline.h"  // _Py_EmscriptenTrampoline_Init()
 #include "pycore_exceptions.h"    // _PyExc_InitTypes()
 #include "pycore_fileutils.h"     // _Py_ResetForceASCII()
 #include "pycore_floatobject.h"   // _PyFloat_InitTypes()
    if (_PyStatus_EXCEPTION(status)) {
        return status;
    }

    _Py_EmscriptenTrampoline_Init();

    return _PyStatus_OK();
 }

diff --git a/configure b/configure
diff --git a/configure.ac b/configure.ac

 AS_CASE([$ac_sys_system],
  [Emscripten], [
    AS_VAR_APPEND([PLATFORM_OBJS], [' Python/emscripten_signal.o'])
    AS_VAR_APPEND([PLATFORM_HEADERS], [' $(srcdir)/Include/internal/pycore_emscripten_signal.h'])
    AS_VAR_APPEND([PLATFORM_OBJS], [' Python/emscripten_signal.o Python/emscripten_trampoline.o'])
    AS_VAR_APPEND([PLATFORM_HEADERS], [' $(srcdir)/Include/internal/pycore_emscripten_signal.h $(srcdir)/Include/internal/pycore_emscripten_trampoline.h'])
  ],
 )
 AC_SUBST([PLATFORM_HEADERS])
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,54 @@
		#ifndef Py_EMSCRIPTEN_TRAMPOLINE_H
		#define Py_EMSCRIPTEN_TRAMPOLINE_H


		/**
		* C function call trampolines to mitigate bad function pointer casts.
		*
		* Section 6.3.2.3, paragraph 8 reads:
		*
		* A pointer to a function of one type may be converted to a pointer to a
		* function of another type and back again; the result shall compare equal to
		* the original pointer. If a converted pointer is used to call a function
		* whose type is not compatible with the pointed-to type, the behavior is
		* undefined.
		*
		* Typical native ABIs ignore additional arguments or fill in missing values
		* with 0/NULL in function pointer cast. Compilers do not show warnings when a
		* function pointer is explicitly casted to an incompatible type.
		*
		* Bad fpcasts are an issue in WebAssembly. WASM's indirect_call has strict
		* function signature checks. Argument count, types, and return type must match.
		*
		* Third party code unintentionally rely on problematic fpcasts. The call
		* trampoline mitigates common occurrences of bad fpcasts on Emscripten.
		*/

		#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)

		void _Py_EmscriptenTrampoline_Init(void);

		PyObject*
		_PyEM_TrampolineCall(PyCFunctionWithKeywords func,
		PyObject* self,
		PyObject* args,
		PyObject* kw);

		#define _PyCFunction_TrampolineCall(meth, self, args) \
		_PyEM_TrampolineCall( \
		((PyCFunctionWithKeywords)(void()(void))(meth)), (self), (args), NULL)

		#define _PyCFunctionWithKeywords_TrampolineCall(meth, self, args, kw) \
		_PyEM_TrampolineCall((meth), (self), (args), (kw))

		#else // defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)

		#define _Py_EmscriptenTrampoline_Init()

		#define _PyCFunction_TrampolineCall(meth, self, args) \
		(meth)((self), (args))
		#define _PyCFunctionWithKeywords_TrampolineCall(meth, self, args, kw) \
		(meth)((self), (args), (kw))

		#endif // defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
		#endif // ndef Py_EMSCRIPTEN_SIGNAL_H
Original file line number	Diff line number	Diff line change
Expand Up		@@ -10,10 +10,13 @@ extern "C" {

		#include <stdbool.h>
		#include "pycore_gc.h" // _PyObject_GC_IS_TRACKED()
		#include "pycore_emscripten_trampoline.h" // _PyCFunction_TrampolineCall()
		#include "pycore_interp.h" // PyInterpreterState.gc
		#include "pycore_pystate.h" // _PyInterpreterState_GET()
		#include "pycore_runtime.h" // _PyRuntime



		/* We need to maintain an internal copy of Py{Var}Object_HEAD_INIT to avoid
		designated initializer conflicts in C++20. If we use the deinition in
		object.h, we will be mixing designated and non-designated initializers in
Expand DownExpand Up		@@ -411,33 +414,6 @@ extern int _PyObject_IsInstanceDictEmpty(PyObject *);

		PyAPI_FUNC(PyObject ) _PyObject_LookupSpecial(PyObject , PyObject *);

		/* C function call trampolines to mitigate bad function pointer casts.
		*
		* Typical native ABIs ignore additional arguments or fill in missing
		* values with 0/NULL in function pointer cast. Compilers do not show
		* warnings when a function pointer is explicitly casted to an
		* incompatible type.
		*
		* Bad fpcasts are an issue in WebAssembly. WASM's indirect_call has strict
		* function signature checks. Argument count, types, and return type must
		* match.
		*
		* Third party code unintentionally rely on problematic fpcasts. The call
		* trampoline mitigates common occurrences of bad fpcasts on Emscripten.
		*/
		#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
		#define _PyCFunction_TrampolineCall(meth, self, args) \
		_PyCFunctionWithKeywords_TrampolineCall( \
		((PyCFunctionWithKeywords)(void()(void))(meth)), (self), (args), NULL)
		extern PyObject* _PyCFunctionWithKeywords_TrampolineCall(
		PyCFunctionWithKeywords meth, PyObject , PyObject , PyObject *);
		#else
		#define _PyCFunction_TrampolineCall(meth, self, args) \
		(meth)((self), (args))
		#define _PyCFunctionWithKeywords_TrampolineCall(meth, self, args, kw) \
		(meth)((self), (args), (kw))
		#endif // __EMSCRIPTEN__ && PY_CALL_TRAMPOLINE

		#ifdef __cplusplus
		}
		#endif
Expand Down
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Changed the way that Emscripten call trampolines work for compatibility with
		Wasm/JS Promise integration.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -18,15 +18,21 @@ class property "propertyobject *" "&PyProperty_Type"

		// see pycore_object.h
		#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
		#include <emscripten.h>
		EM_JS(int, descr_set_trampoline_call, (setter set, PyObject obj, PyObject value, void *closure), {
		return wasmTable.get(set)(obj, value, closure);
		});

		EM_JS(PyObject, descr_get_trampoline_call, (getter get, PyObject obj, void *closure), {
		return wasmTable.get(get)(obj, closure);
		});
		extern PyObject*
		_PyEM_TrampolineCall(PyCFunctionWithKeywords func,
		PyObject* self,
		PyObject* args,
		PyObject* kw);

		#define descr_set_trampoline_call(set, obj, value, closure) \
		((int)_PyEM_TrampolineCall((PyCFunctionWithKeywords)(set), (obj), (value), (PyObject*)(closure)))


		#define descr_get_trampoline_call(get, obj, closure) \
		_PyEM_TrampolineCall((PyCFunctionWithKeywords)(get), (obj), (PyObject*)(closure), NULL)

		#else

		#define descr_set_trampoline_call(set, obj, value, closure) \
		(set)((obj), (value), (closure))

Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -551,10 +551,3 @@ cfunction_call(PyObject func, PyObject args, PyObject *kwargs)
		return _Py_CheckFunctionResult(tstate, func, result, NULL);
		}

		#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
		#include <emscripten.h>

		EM_JS(PyObject, _PyCFunctionWithKeywords_TrampolineCall, (PyCFunctionWithKeywords func, PyObject self, PyObject args, PyObject kw), {
		return wasmTable.get(func)(self, args, kw);
		});
		#endif
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,78 @@
		#if defined(PY_CALL_TRAMPOLINE)

		#include <emscripten.h>
		#include <Python.h>

		static int type_reflection_available;
erlend-aasland marked this conversation as resolved. Show resolvedHide resolved

		/**
		* This is the GoogleChromeLabs approved way to feature detect type-reflection:
		* https://github.com/GoogleChromeLabs/wasm-feature-detect/blob/main/src/detectors/type-reflection/index.js
		*/
		EM_JS(int, _PyEM_detect_type_reflection, (), {
		return "function" in WebAssembly;
		});

		void
		_Py_EmscriptenTrampoline_Init(){
		type_reflection_available = _PyEM_detect_type_reflection();
		}

		/**
		* Backwards compatible trampoline works with all JS runtimes
		*/
		EM_JS_DEPS(_PyEMJS_TrampolineCall, "$getWasmTableEntry")
		EM_JS(PyObject, _PyEMJS_TrampolineCall, (PyCFunctionWithKeywords func, PyObject arg1, PyObject arg2, PyObject arg3), {
		return getWasmTableEntry(func)(arg1, arg2, arg3);
		}
		);
erlend-aasland marked this conversation as resolved. Show resolvedHide resolved

		/**
		* In runtimes with WebAssembly type reflection, count the number of parameters
		* and cast to the appropriate signature
		*/
		EM_JS(int, _PyEM_CountFuncParams, (PyCFunctionWithKeywords func), {
		let n = _PyEM_CountFuncParams.cache.get(func);
		if (n !== undefined) {
		return n;
		}
		n = WebAssembly.Function.type(getWasmTableEntry(func)).parameters.length;
erlend-aasland marked this conversation as resolved. Show resolvedHide resolved
		_PyEM_CountFuncParams.cache.set(func, n);
		return n;
		}
		_PyEM_CountFuncParams.cache = new Map();
		)


		typedef PyObject* (*zero_arg)(void);
		typedef PyObject* (one_arg)(PyObject);
		typedef PyObject* (two_arg)(PyObject, PyObject*);
		typedef PyObject* (three_arg)(PyObject, PyObject, PyObject);


		PyObject*
		_PyEM_TrampolineCall(PyCFunctionWithKeywords func,
		PyObject* self,
		PyObject* args,
		PyObject* kw)
		{
		if (!type_reflection_available) {
		return _PyEMJS_TrampolineCall(func, self, args, kw);
		} else {
		switch (_PyEM_CountFuncParams(func)) {
		case 0:
		return ((zero_arg)func)();
		case 1:
		return ((one_arg)func)(self);
		case 2:
		return ((two_arg)func)(self, args);
		case 3:
		return ((three_arg)func)(self, args, kw);
		default:
		PyErr_SetString(PyExc_SystemError, "Handler takes too many arguments");
		return NULL;
		}
		}
		}

		#endif
Original file line number	Diff line number	Diff line change
Expand Up		@@ -7,6 +7,7 @@
		#include "pycore_codecs.h" // _PyCodec_Lookup()
		#include "pycore_context.h" // _PyContext_Init()
		#include "pycore_dict.h" // _PyDict_Fini()
		#include "pycore_emscripten_trampoline.h" // _Py_EmscriptenTrampoline_Init()
		#include "pycore_exceptions.h" // _PyExc_InitTypes()
		#include "pycore_fileutils.h" // _Py_ResetForceASCII()
		#include "pycore_floatobject.h" // _PyFloat_InitTypes()
Expand DownExpand Up		@@ -542,6 +543,9 @@ pycore_init_runtime(_PyRuntimeState *runtime,
		if (_PyStatus_EXCEPTION(status)) {
		return status;
		}

hoodmane marked this conversation as resolved. Show resolvedHide resolved
		_Py_EmscriptenTrampoline_Init();

		return _PyStatus_OK();
		}

Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -4770,8 +4770,8 @@ PLATFORM_OBJS=

		AS_CASE([$ac_sys_system],
		[Emscripten], [
		AS_VAR_APPEND([PLATFORM_OBJS], [' Python/emscripten_signal.o'])
		AS_VAR_APPEND([PLATFORM_HEADERS], [' $(srcdir)/Include/internal/pycore_emscripten_signal.h'])
		AS_VAR_APPEND([PLATFORM_OBJS], [' Python/emscripten_signal.o Python/emscripten_trampoline.o'])
		AS_VAR_APPEND([PLATFORM_HEADERS], [' $(srcdir)/Include/internal/pycore_emscripten_signal.h $(srcdir)/Include/internal/pycore_emscripten_trampoline.h'])
		],
		)
		AC_SUBST([PLATFORM_HEADERS])
Expand Down