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bpo-47162: Add call trampoline to mitigate bad fpcasts on Emscripten (GH-32189)

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Christian Heimes 2022-03-30 22:28:33 +03:00 • committed by GitHub
parent 795c00b91c
commit 581c4434de
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8 changed files with 99 additions and 18 deletions
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27
Include/internal/pycore_object.h
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@ -242,6 +242,33 @@ extern PyObject* _PyType_GetSubclasses(PyTypeObject *);
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 occurences 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