diff options
Diffstat (limited to 'Include/pymacro.h')
| -rw-r--r-- | Include/pymacro.h | 82 |
1 files changed, 52 insertions, 30 deletions
diff --git a/Include/pymacro.h b/Include/pymacro.h index d410645034d..bfe660e8303 100644 --- a/Include/pymacro.h +++ b/Include/pymacro.h @@ -24,44 +24,66 @@ #endif -// _Py_ALIGN_AS: this compiler's spelling of `alignas` keyword, -// We currently use alignas for free-threaded builds only; additional compat -// checking would be great before we add it to the default build. -// Standards/compiler support: +// _Py_ALIGNED_DEF(N, T): Define a variable/member with increased alignment +// +// `N`: the desired minimum alignment, an integer literal, number of bytes +// `T`: the type of the defined variable +// (or a type with at least the defined variable's alignment) +// +// May not be used on a struct definition. +// +// Standards/compiler support for `alignas` alternatives: // - `alignas` is a keyword in C23 and C++11. // - `_Alignas` is a keyword in C11 // - GCC & clang has __attribute__((aligned)) // (use that for older standards in pedantic mode) // - MSVC has __declspec(align) // - `_Alignas` is common C compiler extension -// Older compilers may name it differently; to allow compilation on such -// unsupported platforms, we don't redefine _Py_ALIGN_AS if it's already +// Older compilers may name `alignas` differently; to allow compilation on such +// unsupported platforms, we don't redefine _Py_ALIGNED_DEF if it's already // defined. Note that defining it wrong (including defining it to nothing) will // cause ABI incompatibilities. -#ifdef Py_GIL_DISABLED -# ifndef _Py_ALIGN_AS -# ifdef __cplusplus -# if __cplusplus >= 201103L -# define _Py_ALIGN_AS(V) alignas(V) -# elif defined(__GNUC__) || defined(__clang__) -# define _Py_ALIGN_AS(V) __attribute__((aligned(V))) -# elif defined(_MSC_VER) -# define _Py_ALIGN_AS(V) __declspec(align(V)) -# else -# define _Py_ALIGN_AS(V) alignas(V) -# endif -# elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L -# define _Py_ALIGN_AS(V) alignas(V) -# elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L -# define _Py_ALIGN_AS(V) _Alignas(V) -# elif (defined(__GNUC__) || defined(__clang__)) -# define _Py_ALIGN_AS(V) __attribute__((aligned(V))) -# elif defined(_MSC_VER) -# define _Py_ALIGN_AS(V) __declspec(align(V)) -# else -# define _Py_ALIGN_AS(V) _Alignas(V) -# endif -# endif +// +// Behavior of `alignas` alternatives: +// - `alignas` & `_Alignas`: +// - Can be used multiple times; the greatest alignment applies. +// - It is an *error* if the combined effect of all `alignas` modifiers would +// decrease the alignment. +// - Takes types or numbers. +// - May not be used on a struct definition, unless also defining a variable. +// - `__declspec(align)`: +// - Has no effect if it would decrease alignment. +// - Only takes an integer literal. +// - May be used on struct or variable definitions. +// However, when defining both the struct and the variable at once, +// `declspec(aligned)` causes compiler warning 5274 and possible ABI +// incompatibility. +// - ` __attribute__((aligned))`: +// - Has no effect if it would decrease alignment. +// - Takes types or numbers +// - May be used on struct or variable definitions. +#ifndef _Py_ALIGNED_DEF +# ifdef __cplusplus +# if __cplusplus >= 201103L +# define _Py_ALIGNED_DEF(N, T) alignas(N) alignas(T) T +# elif defined(__GNUC__) || defined(__clang__) +# define _Py_ALIGNED_DEF(N, T) __attribute__((aligned(N))) T +# elif defined(_MSC_VER) +# define _Py_ALIGNED_DEF(N, T) __declspec(align(N)) T +# else +# define _Py_ALIGNED_DEF(N, T) alignas(N) alignas(T) T +# endif +# elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L +# define _Py_ALIGNED_DEF(N, T) alignas(N) alignas(T) T +# elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L +# define _Py_ALIGNED_DEF(N, T) _Alignas(N) _Alignas(T) T +# elif (defined(__GNUC__) || defined(__clang__)) +# define _Py_ALIGNED_DEF(N, T) __attribute__((aligned(N))) T +# elif defined(_MSC_VER) +# define _Py_ALIGNED_DEF(N, T) __declspec(align(N)) T +# else +# define _Py_ALIGNED_DEF(N, T) _Alignas(N) _Alignas(T) T +# endif #endif /* Minimum value between x and y */ |