diff --git a/Include/cpython/object.h b/Include/cpython/object.h index 973d358ed8e4ec7..bc10958e867e1a5 100644 --- a/Include/cpython/object.h +++ b/Include/cpython/object.h @@ -331,9 +331,9 @@ PyAPI_FUNC(PyObject *) _PyObject_FunctionStr(PyObject *); * `dst` points to a valid object. * * Temporary variables are used to only evaluate macro arguments once and so - * avoid the duplication of side effects. _Py_TYPEOF() or memcpy() is used to - * avoid a miscompilation caused by type punning. See Py_CLEAR() comment for - * implementation details about type punning. + * avoid the duplication of side effects. _Py_TYPEOF(), C++ auto, or memcpy() + * is used to avoid a miscompilation caused by type punning. See Py_CLEAR() + * comment for implementation details about type punning. * * The memcpy() implementation does not emit a compiler warning if 'src' has * not the same type than 'src': any pointer type is accepted for 'src'. @@ -341,11 +341,19 @@ PyAPI_FUNC(PyObject *) _PyObject_FunctionStr(PyObject *); #ifdef _Py_TYPEOF #define Py_SETREF(dst, src) \ do { \ - _Py_TYPEOF(dst)* _tmp_dst_ptr = &(dst); \ + _Py_TYPEOF(&(dst)) _tmp_dst_ptr = &(dst); \ _Py_TYPEOF(dst) _tmp_old_dst = (*_tmp_dst_ptr); \ *_tmp_dst_ptr = (src); \ Py_DECREF(_tmp_old_dst); \ } while (0) +#elif defined(__cplusplus) && (__cplusplus >= 201103L || _MSVC_LANG >= 201103L) +#define Py_SETREF(dst, src) \ + do { \ + auto _tmp_dst_ptr = &(dst); \ + auto _tmp_old_dst = (*_tmp_dst_ptr); \ + *_tmp_dst_ptr = (src); \ + Py_DECREF(_tmp_old_dst); \ + } while (0) #else #define Py_SETREF(dst, src) \ do { \ @@ -363,11 +371,19 @@ PyAPI_FUNC(PyObject *) _PyObject_FunctionStr(PyObject *); #ifdef _Py_TYPEOF #define Py_XSETREF(dst, src) \ do { \ - _Py_TYPEOF(dst)* _tmp_dst_ptr = &(dst); \ + _Py_TYPEOF(&(dst)) _tmp_dst_ptr = &(dst); \ _Py_TYPEOF(dst) _tmp_old_dst = (*_tmp_dst_ptr); \ *_tmp_dst_ptr = (src); \ Py_XDECREF(_tmp_old_dst); \ } while (0) +#elif defined(__cplusplus) && (__cplusplus >= 201103L || _MSVC_LANG >= 201103L) +#define Py_XSETREF(dst, src) \ + do { \ + auto _tmp_dst_ptr = &(dst); \ + auto _tmp_old_dst = (*_tmp_dst_ptr); \ + *_tmp_dst_ptr = (src); \ + Py_XDECREF(_tmp_old_dst); \ + } while (0) #else #define Py_XSETREF(dst, src) \ do { \ diff --git a/Include/pymacro.h b/Include/pymacro.h index 1af057ad78266af..937025ae2e60a1f 100644 --- a/Include/pymacro.h +++ b/Include/pymacro.h @@ -130,23 +130,27 @@ } while(0) #endif -/* Get the number of elements in a visible array - - This does not work on pointers, or arrays declared as [], or function - parameters. With correct compiler support, such usage will cause a build - error (see Py_BUILD_ASSERT_EXPR). - - Written by Rusty Russell, public domain, http://ccodearchive.net/ - - Requires at GCC 3.1+ */ -#if (defined(__GNUC__) && !defined(__STRICT_ANSI__) && \ - (((__GNUC__ == 3) && (__GNUC_MINOR__ >= 1)) || (__GNUC__ >= 4))) -/* Two gcc extensions. - &a[0] degrades to a pointer: a different type from an array */ +// Get the number of elements in a visible array. +// +// This does not work on pointers, or arrays declared as [], or function +// parameters. With correct compiler support, such usage will cause a build +// error (see Py_BUILD_ASSERT_EXPR). +// +// Written by Rusty Russell, public domain, http://ccodearchive.net/ +// +// Require GCC 4 (it works on GCC 3.1). +// +// Two GCC extensions: &a[0] degrades to a pointer, a different type from an +// array. +// +// gh-158810: Do not use __builtin_types_compatible_p() in strict C ANSI mode +// and on C++. +#if (defined(__GNUC__) && __GNUC__ >= 4 && defined(_Py_TYPEOF) \ + && !defined(__STRICT_ANSI__) && !defined(__cplusplus)) #define Py_ARRAY_LENGTH(array) \ (sizeof(array) / sizeof((array)[0]) \ - + Py_BUILD_ASSERT_EXPR(!__builtin_types_compatible_p(typeof(array), \ - typeof(&(array)[0])))) + + Py_BUILD_ASSERT_EXPR(!__builtin_types_compatible_p(_Py_TYPEOF(array), \ + _Py_TYPEOF(&(array)[0])))) #else #define Py_ARRAY_LENGTH(array) \ (sizeof(array) / sizeof((array)[0])) diff --git a/Include/pyport.h b/Include/pyport.h index 22820884b45fb70..b8e60d3bd359fca 100644 --- a/Include/pyport.h +++ b/Include/pyport.h @@ -565,8 +565,15 @@ extern "C" { // // Example: _Py_TYPEOF(x) x_copy = (x); // -// The macro is only defined if GCC or clang compiler is used. -#if defined(__GNUC__) || defined(__clang__) +// On C23, use typeof(). Otherwise, use __typeof__() +// if on GCC, clang or MSVC 17.9 and newer. +// +// gh-157649: Do not use decltype() on C++, since it produces invalid code in +// Py_CLEAR()/Py_SETREF(). +#if defined (__STDC_VERSION__) && __STDC_VERSION__ >= 202311L +# define _Py_TYPEOF(expr) typeof(expr) +#elif (defined(__GNUC__) || defined(__clang__) \ + || (defined(_MSC_VER) && _MSC_VER >= 1939 && !defined(__cplusplus))) # define _Py_TYPEOF(expr) __typeof__(expr) #endif diff --git a/Include/refcount.h b/Include/refcount.h index 03da93b53c2438c..e0730606646430e 100644 --- a/Include/refcount.h +++ b/Include/refcount.h @@ -472,17 +472,30 @@ static inline Py_ALWAYS_INLINE void Py_DECREF(PyObject *op) * and so avoid type punning. Otherwise, use memcpy() which causes type erasure * and so prevents the compiler to reuse an old cached 'op' value after * Py_CLEAR(). + * + * On C++11 and newer, use "auto". On MSVC, check also _MSVC_LANG since + * __cplusplus is 199711L unless the /Zc:__cplusplus flag is used. */ #ifdef _Py_TYPEOF #define Py_CLEAR(op) \ do { \ - _Py_TYPEOF(op)* _tmp_op_ptr = &(op); \ + _Py_TYPEOF(&(op)) _tmp_op_ptr = &(op); \ _Py_TYPEOF(op) _tmp_old_op = (*_tmp_op_ptr); \ if (_tmp_old_op != _Py_NULL) { \ *_tmp_op_ptr = _Py_NULL; \ Py_DECREF(_tmp_old_op); \ } \ } while (0) +#elif defined(__cplusplus) && (__cplusplus >= 201103L || _MSVC_LANG >= 201103L) +#define Py_CLEAR(op) \ + do { \ + auto _tmp_op_ptr = &(op); \ + auto _tmp_old_op = (*_tmp_op_ptr); \ + if (_tmp_old_op != _Py_NULL) { \ + *_tmp_op_ptr = _Py_NULL; \ + Py_DECREF(_tmp_old_op); \ + } \ + } while (0) #else #define Py_CLEAR(op) \ do { \ diff --git a/Lib/test/test_cext/extension.c b/Lib/test/test_cext/extension.c index 5dcac39f8750db1..109d809b4db059f 100644 --- a/Lib/test/test_cext/extension.c +++ b/Lib/test/test_cext/extension.c @@ -85,6 +85,8 @@ test_macros(PyObject *Py_UNUSED(module), PyObject *Py_UNUSED(args)) #ifndef Py_LIMITED_API PyObject *dict; #endif + PyObject *slots[1]; + int small_array[] = {2, 5, 7}; // test Py_BUILD_ASSERT() and Py_BUILD_ASSERT_EXPR() Py_BUILD_ASSERT(sizeof(int) == sizeof(unsigned int)); @@ -100,17 +102,32 @@ test_macros(PyObject *Py_UNUSED(module), PyObject *Py_UNUSED(args)) Py_CLEAR(obj); assert(obj == _Py_NULL); + // gh-157649: Test Py_CLEAR() on an array + slots[0] = Py_None; + Py_CLEAR(slots[0]); + assert(slots[0] == _Py_NULL); + #ifndef Py_LIMITED_API // Test Py_SETREF(): use typeof()/__typeof__() if available, or memcpy() obj = Py_None; Py_SETREF(obj, _Py_NULL); assert(obj == _Py_NULL); + // gh-157649: Test Py_SETREF() on an array + slots[0] = Py_None; + Py_SETREF(slots[0], _Py_NULL); + assert(slots[0] == _Py_NULL); + // Test Py_XSETREF(): use typeof()/__typeof__() if available, or memcpy() obj = Py_None; Py_XSETREF(obj, _Py_NULL); assert(obj == _Py_NULL); + // gh-157649: Test Py_XSETREF() on an array + slots[0] = Py_None; + Py_XSETREF(slots[0], _Py_NULL); + assert(slots[0] == _Py_NULL); + // Test that Py_BEGIN_CRITICAL_SECTION is available dict = PyDict_New(); if (dict == NULL) { @@ -119,7 +136,10 @@ test_macros(PyObject *Py_UNUSED(module), PyObject *Py_UNUSED(args)) Py_BEGIN_CRITICAL_SECTION(dict); Py_END_CRITICAL_SECTION(); Py_DECREF(dict); -#endif +#endif // !Py_LIMITED_API + + // Test Py_ARRAY_LENGTH() + assert(Py_ARRAY_LENGTH(small_array) == 3); Py_RETURN_NONE; } diff --git a/Lib/test/test_cext/setup.py b/Lib/test/test_cext/setup.py index 60337064a72a5c6..0d2f1915fadda02 100644 --- a/Lib/test/test_cext/setup.py +++ b/Lib/test/test_cext/setup.py @@ -149,7 +149,7 @@ def main(): # option emits a C++ compiler warning. Remove "-std11" option from the # CC command. cmd = (sysconfig.get_config_var('CC') or '') - if cmd is not None: + if cmd is not None and 'CC' not in os.environ: if support.MS_WINDOWS: std_prefix = '/std' else: diff --git a/Misc/NEWS.d/next/C_API/2026-10-05-01-09-32.gh-issue-158810.F1p-PK.rst b/Misc/NEWS.d/next/C_API/2026-10-05-01-09-32.gh-issue-158810.F1p-PK.rst new file mode 100644 index 000000000000000..8d0878fd057a04b --- /dev/null +++ b/Misc/NEWS.d/next/C_API/2026-10-05-01-09-32.gh-issue-158810.F1p-PK.rst @@ -0,0 +1,2 @@ +Fix :c:macro:`Py_ARRAY_LENGTH()` macro on C++: do not use +``__builtin_types_compatible_p()`` on C++. Patch by Victor Stinner.