improvements of more than 500x overthe state-of-the-art Compilertakes in standard Unified Robot Description Format (URDF) files and generates optimized code Setup data structure to optimize SIMD execution Skip

CppCon 2021 Independently developed libraries Linker error: duplicate definition for exported symbols ‘f()’, needed by ‘lib_m1()’ and ‘lib_m2()’. Non-compositional semanticsStrong Module Ownership ▪ The MSVC toolset relies on the Abstract Semantics Graph (ASG) of a TU, persisted in the IFC format, Binary Module Interface (BMI)! – ASG contains all meaningful semantics information from the input symbol – The linker must build two sets: ▪ References to external linkage symbols ▪ Definitions of external linkage symbols – For external linkage names the “great hunt” begins… – If two definitions

composition Visibility of Identifiers vs. Reachability of Declarations Relationships, linkage and linker symbols Modules in practice Moving towards modules (by example) Imports are different! Is it worth it namespace name '::A' is attached to the global module, as it is oblivious of module boundaries 21LINKER SYMBOLS export module mod3; int foo(); // module linkage, attached to module 'mod3' namespace 'mod3' return foo(); } } // namespace A 1 2 3 4 5 6 7 8 9 Strong ownership model, the linker symbols of exported names contain the module name they are attached to e.g. msvc Benefit: Identical

addresses as resolved by the loader … … … https://learn.microsoft.com/en-us/windows/win32/debug/pe-format#the-idata-section 10 * Actually in section .rdata… .idata lib1: f1, f2, f3 lib2: g1, g2, g3 `global' can not be used when making a shared object; recompile with -fPIC • -fpic vs –fpie: • EXE symbols are relocatable but NOT interposable. Interprocedural optimizations apply. 24Lazy Binding (a linking against an import library • Minor optimization that happens in Release anyway • Most symbols are neither. exe ... call f() ... .idata dll1: __imp_f f(): jmp __imp_f() 41Symbol Visibility

defined on the slide ●hello, units using namespace mp_units::si::unit_symbols; using namespace mp_units::international::unit_symbols; constexpr quantity v1 = 110 * (km / h); // 110 km/h constexpr quantity : named_unit<"16th", mag * EigthNote> {} SixteenthNote; // ... }namespace ni::unit_symbols { inline constexpr auto n_wd = 3 * HalfNote; inline constexpr auto n_w = WholeNote; inline constexpr constexpr auto n_8th = EigthNote; inline constexpr auto n_16th = SixteenthNote; }namespace ni::unit_symbols { inline constexpr auto n_wd = 3 * HalfNote; inline constexpr auto n_w = WholeNote; inline constexpr

CppCon 2021 | • Portable Executable format (PE) – exe, dll, etc. on Windows • Executable and Linkable Format (ELF) – for UNIX and UNIX-like OS • Mach Object file format (Mach-O) – executable, dylib, bundle if any call failed APIs: Win3211 CppCon 2021 | • dumpbin /exports repromath.dll Checkout what symbols are exported13 CppCon 2021 | double x[] = {1., 2., 3.}; double y[] = {4., -5., 6.}; auto lib = of the last error in dl APIs: POSIX15 CppCon 2021 | • objdump -T librepromath.so Checkout what symbols are exported17 CppCon 2021 | double x[] = {1., 2., 3.}; double y[] = {4., -5., 6.}; auto lib =

config_register.ld main.o objdump -ds config.out 8 . 10/ $ ./build.sh config.out: file format elf64-x86-64 Contents of section .config_registers: 0100 fd000002 fc000003 minimum metadata size 10 . 3/ $ objdump -s --section=.compressedmap example example: file format elf64-x86-64 Contents of section .compressedmap: 20c0 00000000 00000000 01000000 00000000 01006400 ' ( d 10 . 4/ Huffman coding (overview) Optimal encoding given the list of symbols and their frequency symbols are all characters in all strings Uses a min-heap priority_queue to build a tree bottom

namespace wikipedia { class article { public: std::string format(); // symbol: _ZN9wikipedia7article6formatB5cxx11Ev }; } std::string format(std::string const& fmt, int64_t val); // symbol: _Z6form to find their symbols • It determines a set of all symbols that are used by the program • It resolves references to internal and external symbols • It assigns addresses to the symbols representing functions

Allows or disallows undefined symbols in shared libraries. This switch is similar to --no-undefined except that it determines the behaviour when the undefined symbols are in a shared does not affect how undefined symbols in regular object files are handled. The default behaviour is to report errors for any undefined symbols referenced in shared libraries dependencies / missing symbols libfoo.so libbar.so libmylib.so Linux ✅❓Indirect dependencies / missing symbols libfoo.so libbar.so libmylib.so macOS: errorIndirect dependencies / missing symbols libfoo.so libbar

specified/returned if the ContextFlags word // contains the flag CONTEXT_EXTENDED_REGISTERS. // The format and contexts are processor specific BYTE ExtendedRegisters[MAXIMUM_SUPPORTED_EXTENSION]; swprintf_s(buf, MSG_BUFFER_LEN, L"%hs (0x%.8x) at address " ADDRESS_FORMAT SW_EOL, "ACCESS_VIOLATION", EXCEPTION_ACCESS_VIOLATION, aE wchar_t buf[MSG_BUFFER_LEN]; swprintf_s(buf, MSG_BUFFER_LEN, L"(0x%.8x) at address " ADDRESS_FORMAT SW_EOL, aExceptionInfo->ExceptionRecord->ExceptionCode, aExceptionIn