psABI: ARM, x86, … C++ Itanium ABI Microsoft Windows ABIs C++ Standard 18armv8-a System V ABI - iPhone - M1 Mac and newer - Android smartphone x86-64 (AMD64) System V ABI - Linux server - old Mac (AMD64) Microsoft ABI - Windows device armv7-a System V ABI - ancient iPhone - low-end Android smartphone x86 (IA-32) System V ABI - ancient Linux server x86 (IA-32) Microsoft ABI - ancient Windows Windows device 19armv8-a System V ABI Procedure Call Standard for the Arm® 64-bit Architecture armv8-a clang 18.1.0 -O2 -std=c++20 x86-64 (AMD64) System V ABI AMD64 Architecture Processor Supplement

mo/src/main.cpp:70 frame #1 : 0x0000555555583b08 in std::__1::coroutine_handle::resume[abi:ne180100]() const () at /usr/lib/llvm-18/include/c++/v1/__coroutine/coroutine_handle.h:69 frame namespace)::word_stats, fal frame #1 : 0x0000555555583b08 in std::__1::coroutine_handle::resume[abi:ne180100]() co frame #2 : 0x0000555555584045 in unifex::_ch::continuation_handle::resume() namespace)::word_stats, false>::type ( 1 : 0x0000555555583b08 in std::__1::coroutine_handle::resume[abi:ne180100]() const () at / 2 : 0x0000555555584045 in unifex::_ch::continuation_handle::resume()

= basic_simd_mask; template Abi = ...> class basic_simd; template Abi> class basic_simd_mask; • simd behaves just like T (element-wise) vs. element-sized masks (array of bool is not unheard of), • SIMD width simd::size • Abi determines width and ABI (i.e. how parameters are passed to functions) • Example: simd on x86 can be two = basic_simd_mask; template Abi = ...> class basic_simd; template Abi> class basic_simd_mask; • simd behaves just like T (element-wise)

short for ABI compatibility with C c_ushort unsigned short for ABI compatibility with C c_int int for ABI compatibility with C c_uint unsigned int for ABI compatibility with C c_long long for ABI compatibility unsigned long for ABI compatibility with C c_longlong long long for ABI compatibility with C c_ulonglong unsigned long long for ABI compatibility with C c_longdouble long double for ABI compatibility with with C c_void void for ABI compatibility with C f16 _Float16 16-bit floating point (10-bit mantissa) IEEE-754-2008 binary16 f32 float 32-bit floating point (23-bit mantissa) IEEE-754-2008 binary32

short for ABI compatibility with C c_ushort unsigned short for ABI compatibility with C c_int int for ABI compatibility with C c_uint unsigned int for ABI compatibility with C c_long long for ABI compatibility unsigned long for ABI compatibility with C c_longlong long long for ABI compatibility with C c_ulonglong unsigned long long for ABI compatibility with C c_longdouble long double for ABI compatibility with with C c_void void for ABI compatibility with C f16 _Float16 16-bit floating point (10-bit mantissa) IEEE-754-2008 binary16 f32 float 32-bit floating point (23-bit mantissa) IEEE-754-2008 binary32

short for ABI compatibility with C c_ushort unsigned short for ABI compatibility with C c_int int for ABI compatibility with C c_uint unsigned int for ABI compatibility with C c_long long for ABI compatibility unsigned long for ABI compatibility with C c_longlong long long for ABI compatibility with C c_ulonglong unsigned long long for ABI compatibility with C c_longdouble long double for ABI compatibility with with C c_void void for ABI compatibility with C f16 _Float16 16-bit floating point (10-bit mantissa) IEEE-754- 2008 binary16 f32 float 32-bit floating point (23-bit mantissa) IEEE-754- 2008 binary32

short for ABI compatibility with C c_ushort unsigned short for ABI compatibility with C c_int int for ABI compatibility with C c_uint unsigned int for ABI compatibility with C c_long long for ABI compatibility unsigned long for ABI compatibility with C c_longlong long long for ABI compatibility with C c_ulonglong unsigned long long for ABI compatibility with C c_longdouble long double for ABI compatibility with with C c_void void for ABI compatibility with C f16 _Float16 16-bit floating point (10-bit mantissa) IEEE-754- 2008 binary16 f32 float 32-bit floating point (23-bit mantissa) IEEE-754- 2008 binary32

short for ABI compatibility with C c_ushort unsigned short for ABI compatibility with C c_int int for ABI compatibility with C c_uint unsigned int for ABI compatibility with C c_long long for ABI compatibility unsigned long for ABI compatibility with C c_longlong long long for ABI compatibility with C c_ulonglong unsigned long long for ABI compatibility with C c_longdouble long double for ABI compatibility with with C c_void void for ABI compatibility with C f16 _Float16 16-bit floating point (10-bit mantissa) IEEE-754- 2008 binary16 f32 float 32-bit floating point (23-bit mantissa) IEEE-754- 2008 binary32

Reflection in C++ as per P2996 Syntax and examples Reflection libraries! Python bindings ABI hashing (boost::abi_hash?) A duck-typed std::any (boost::virtual_any?) Alternatives ways to achieve “reflection” Reflection libaries! 42Now let's do some actual library design Automatic python bindings Automatic type ABI hash A better std::any with duck typing 43Python bindings 44We have a C++ class that we’d like to Customizations are trickier / not DRY We have two potential approaches Python bindings - Summary 54ABI hashing 55Say you had a unique hash for a type’s memory layout. What would you do? We’d like

for ABI compatibility with C c_short short for ABI compatibility with C c_ushort unsigned short for ABI compatibility with C c_int int for ABI compatibility with C c_uint unsigned int for ABI compatibility c_long long for ABI compatibility with C c_ulong unsigned long for ABI compatibility with C c_longlong long long for ABI compatibility with C c_ulonglong unsigned long long for ABI compatibility with with C c_longdouble long double for ABI compatibility with C f16 _Float16 16-bit floating point (10-bit mantissa) IEEE-754-2008 binary16 f32 float 32-bit floating point (23-bit mantissa) IEEE-754- 2008