From 29e2245ad5d28b565fe0d0d667d283708c6e832c Mon Sep 17 00:00:00 2001 From: Victor Stinner Date: Wed, 27 Apr 2022 10:40:57 +0200 Subject: [PATCH] gh-91320: Add _Py_reinterpret_cast() macro (#91959) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Fix C++ compiler warnings about "old-style cast" (g++ -Wold-style-cast) in the Python C API. Use C++ reinterpret_cast<> and static_cast<> casts when the Python C API is used in C++. Example of fixed warning: Include/object.h:107:43: error: use of old-style cast to ‘PyObject*’ {aka ‘struct _object*’} [-Werror=old-style-cast] #define _PyObject_CAST(op) ((PyObject*)(op)) Add _Py_reinterpret_cast() and _Py_static_cast() macros. --- Include/cpython/abstract.h | 3 ++- Include/cpython/listobject.h | 3 ++- Include/cpython/methodobject.h | 6 ++++-- Include/cpython/tupleobject.h | 3 ++- Include/cpython/unicodeobject.h | 9 ++++++--- Include/methodobject.h | 4 +++- Include/object.h | 7 ++++--- Include/objimpl.h | 4 ++-- Include/pyport.h | 17 ++++++++++++++--- ...022-04-26-16-51-31.gh-issue-91320.QDHmTv.rst | 3 +++ 10 files changed, 42 insertions(+), 17 deletions(-) create mode 100644 Misc/NEWS.d/next/C API/2022-04-26-16-51-31.gh-issue-91320.QDHmTv.rst diff --git a/Include/cpython/abstract.h b/Include/cpython/abstract.h index bdc0c49cd4c..42f766da991 100644 --- a/Include/cpython/abstract.h +++ b/Include/cpython/abstract.h @@ -50,7 +50,8 @@ PyAPI_FUNC(PyObject *) _PyObject_MakeTpCall( PyObject *const *args, Py_ssize_t nargs, PyObject *keywords); -#define PY_VECTORCALL_ARGUMENTS_OFFSET ((size_t)1 << (8 * sizeof(size_t) - 1)) +#define PY_VECTORCALL_ARGUMENTS_OFFSET \ + (_Py_static_cast(size_t, 1) << (8 * sizeof(size_t) - 1)) static inline Py_ssize_t PyVectorcall_NARGS(size_t n) diff --git a/Include/cpython/listobject.h b/Include/cpython/listobject.h index 0cd69216a4c..298bfcbf143 100644 --- a/Include/cpython/listobject.h +++ b/Include/cpython/listobject.h @@ -25,7 +25,8 @@ PyAPI_FUNC(PyObject *) _PyList_Extend(PyListObject *, PyObject *); PyAPI_FUNC(void) _PyList_DebugMallocStats(FILE *out); /* Cast argument to PyListObject* type. */ -#define _PyList_CAST(op) (assert(PyList_Check(op)), (PyListObject *)(op)) +#define _PyList_CAST(op) \ + (assert(PyList_Check(op)), _Py_reinterpret_cast(PyListObject*, (op))) // Macros and static inline functions, trading safety for speed diff --git a/Include/cpython/methodobject.h b/Include/cpython/methodobject.h index 46d177793fc..68cecfe05ba 100644 --- a/Include/cpython/methodobject.h +++ b/Include/cpython/methodobject.h @@ -8,9 +8,11 @@ PyAPI_DATA(PyTypeObject) PyCMethod_Type; #define PyCMethod_Check(op) PyObject_TypeCheck(op, &PyCMethod_Type) #define _PyCFunctionObject_CAST(func) \ - (assert(PyCFunction_Check(func)), (PyCFunctionObject *)(func)) + (assert(PyCFunction_Check(func)), \ + _Py_reinterpret_cast(PyCFunctionObject*, (func))) #define _PyCMethodObject_CAST(func) \ - (assert(PyCMethod_Check(func)), (PyCMethodObject *)(func)) + (assert(PyCMethod_Check(func)), \ + _Py_reinterpret_cast(PyCMethodObject*, (func))) /* Macros for direct access to these values. Type checks are *not* done, so use with care. */ diff --git a/Include/cpython/tupleobject.h b/Include/cpython/tupleobject.h index fd15ecd1c77..8089e2409ce 100644 --- a/Include/cpython/tupleobject.h +++ b/Include/cpython/tupleobject.h @@ -14,7 +14,8 @@ PyAPI_FUNC(int) _PyTuple_Resize(PyObject **, Py_ssize_t); PyAPI_FUNC(void) _PyTuple_MaybeUntrack(PyObject *); /* Cast argument to PyTupleObject* type. */ -#define _PyTuple_CAST(op) (assert(PyTuple_Check(op)), (PyTupleObject *)(op)) +#define _PyTuple_CAST(op) \ + (assert(PyTuple_Check(op)), _Py_reinterpret_cast(PyTupleObject*, (op))) // Macros and static inline functions, trading safety for speed diff --git a/Include/cpython/unicodeobject.h b/Include/cpython/unicodeobject.h index 2712c583270..0397f12a826 100644 --- a/Include/cpython/unicodeobject.h +++ b/Include/cpython/unicodeobject.h @@ -236,11 +236,14 @@ PyAPI_FUNC(int) _PyUnicode_CheckConsistency( #define _PyASCIIObject_CAST(op) \ - (assert(PyUnicode_Check(op)), (PyASCIIObject*)(op)) + (assert(PyUnicode_Check(op)), \ + _Py_reinterpret_cast(PyASCIIObject*, (op))) #define _PyCompactUnicodeObject_CAST(op) \ - (assert(PyUnicode_Check(op)), (PyCompactUnicodeObject*)(op)) + (assert(PyUnicode_Check(op)), \ + _Py_reinterpret_cast(PyCompactUnicodeObject*, (op))) #define _PyUnicodeObject_CAST(op) \ - (assert(PyUnicode_Check(op)), (PyUnicodeObject*)(op)) + (assert(PyUnicode_Check(op)), \ + _Py_reinterpret_cast(PyUnicodeObject*, (op))) /* --- Flexible String Representation Helper Macros (PEP 393) -------------- */ diff --git a/Include/methodobject.h b/Include/methodobject.h index 959e7751220..2046ab948de 100644 --- a/Include/methodobject.h +++ b/Include/methodobject.h @@ -42,7 +42,9 @@ typedef PyObject *(*PyCMethod)(PyObject *, PyTypeObject *, PyObject *const *, // used to prevent a compiler warning. If the function has a single parameter, // it triggers an undefined behavior when Python calls it with 2 parameters // (bpo-33012). -#define _PyCFunction_CAST(func) ((PyCFunction)(void(*)(void))(func)) +#define _PyCFunction_CAST(func) \ + _Py_reinterpret_cast(PyCFunction, \ + _Py_reinterpret_cast(void(*)(void), (func))) PyAPI_FUNC(PyCFunction) PyCFunction_GetFunction(PyObject *); PyAPI_FUNC(PyObject *) PyCFunction_GetSelf(PyObject *); diff --git a/Include/object.h b/Include/object.h index 5622305f49f..c51f12b6562 100644 --- a/Include/object.h +++ b/Include/object.h @@ -104,7 +104,7 @@ struct _object { }; /* Cast argument to PyObject* type. */ -#define _PyObject_CAST(op) ((PyObject*)(op)) +#define _PyObject_CAST(op) _Py_reinterpret_cast(PyObject*, (op)) typedef struct { PyObject ob_base; @@ -112,7 +112,7 @@ typedef struct { } PyVarObject; /* Cast argument to PyVarObject* type. */ -#define _PyVarObject_CAST(op) ((PyVarObject*)(op)) +#define _PyVarObject_CAST(op) _Py_reinterpret_cast(PyVarObject*, (op)) // Test if the 'x' object is the 'y' object, the same as "x is y" in Python. @@ -780,7 +780,8 @@ static inline int PyType_Check(PyObject *op) { # define PyType_Check(op) PyType_Check(_PyObject_CAST(op)) #endif -#define _PyType_CAST(op) (assert(PyType_Check(op)), (PyTypeObject*)(op)) +#define _PyType_CAST(op) \ + (assert(PyType_Check(op)), _Py_reinterpret_cast(PyTypeObject*, (op))) static inline int PyType_CheckExact(PyObject *op) { return Py_IS_TYPE(op, &PyType_Type); diff --git a/Include/objimpl.h b/Include/objimpl.h index 9b98c112ac2..94e03045f88 100644 --- a/Include/objimpl.h +++ b/Include/objimpl.h @@ -182,9 +182,9 @@ PyAPI_FUNC(void) PyObject_GC_UnTrack(void *); PyAPI_FUNC(void) PyObject_GC_Del(void *); #define PyObject_GC_New(type, typeobj) \ - ( (type *) _PyObject_GC_New(typeobj) ) + _Py_reinterpret_cast(type*, _PyObject_GC_New(typeobj)) #define PyObject_GC_NewVar(type, typeobj, n) \ - ( (type *) _PyObject_GC_NewVar((typeobj), (n)) ) + _Py_reinterpret_cast(type*, _PyObject_GC_NewVar((typeobj), (n))) PyAPI_FUNC(int) PyObject_GC_IsTracked(PyObject *); PyAPI_FUNC(int) PyObject_GC_IsFinalized(PyObject *); diff --git a/Include/pyport.h b/Include/pyport.h index 855c382a61e..5102f7487d2 100644 --- a/Include/pyport.h +++ b/Include/pyport.h @@ -14,6 +14,16 @@ #endif +// Macro to use C++ static_cast<> and reinterpret_cast<> in the Python C API +#ifdef __cplusplus +# define _Py_static_cast(type, expr) static_cast(expr) +# define _Py_reinterpret_cast(type, expr) reinterpret_cast(expr) +#else +# define _Py_static_cast(type, expr) ((type)(expr)) +# define _Py_reinterpret_cast(type, expr) ((type)(expr)) +#endif + + /* Defines to build Python and its standard library: * * - Py_BUILD_CORE: Build Python core. Give access to Python internals, but @@ -295,10 +305,11 @@ extern "C" { * VALUE may be evaluated more than once. */ #ifdef Py_DEBUG -#define Py_SAFE_DOWNCAST(VALUE, WIDE, NARROW) \ - (assert((WIDE)(NARROW)(VALUE) == (VALUE)), (NARROW)(VALUE)) +# define Py_SAFE_DOWNCAST(VALUE, WIDE, NARROW) \ + (assert((WIDE)(NARROW)(VALUE) == (VALUE)), (NARROW)(VALUE)) #else -#define Py_SAFE_DOWNCAST(VALUE, WIDE, NARROW) (NARROW)(VALUE) +# define Py_SAFE_DOWNCAST(VALUE, WIDE, NARROW) \ + _Py_reinterpret_cast(NARROW, (VALUE)) #endif diff --git a/Misc/NEWS.d/next/C API/2022-04-26-16-51-31.gh-issue-91320.QDHmTv.rst b/Misc/NEWS.d/next/C API/2022-04-26-16-51-31.gh-issue-91320.QDHmTv.rst new file mode 100644 index 00000000000..07e27acd4f6 --- /dev/null +++ b/Misc/NEWS.d/next/C API/2022-04-26-16-51-31.gh-issue-91320.QDHmTv.rst @@ -0,0 +1,3 @@ +Fix C++ compiler warnings about "old-style cast" (``g++ -Wold-style-cast``) in +the Python C API. Use C++ ``reinterpret_cast<>`` and ``static_cast<>`` casts +when the Python C API is used in C++. Patch by Victor Stinner.