object file 6 . 1 some header.h other header.h program other header.h other header.h Barrier→║ traditional librarylibrary.cpp source.cpp library.h other header.h declarations macros compiler defaults, commandline none translation unit files object file 6 . 2 discarded discarded some header.hsource.cpp translation unit object file export module library; library interface unit module Interface partition ✅ ✅ ❎ ✅ ✅ ✅ Implementation partition ✅ ❎ ✅ ❎ ✅ Private module fragment ✅ ✅ Header unit ✅ ✅ ✅ ✅ ✅ ✅ Defines interface contributes to interface implicitly imports interface part

size() < p_thrown_size + sizeof(exception_header)) { std::terminate(); } return exception_storage.data() + sizeof(exception_header); } Exception Header (all the things the exception runtime needs register_t sp; register_t lr; register_t pc; }; Itanium C++ ABI: What is the Exception Header? struct exception_header { cortex_m_cpu cpu{}; std::type_info* type_info; destructor_t* destructor; cache_t { std::uint32_t state_and_rel_address; const index_entry_t* entry_ptr; } 110Exception Header (all the things the exception runtime needs to remember during unwinding) Thrown Object Returned

One Definition Rule is your friend – Named modules provide ODR guarantees, by design – Header files and header units require (expensive) incomplete ODR checks, and demand complete trust 4 (C) Dos Reis this principle ▪ Headers vs header units vs named modules ▪ Spectacular improvement in compile-time performance 23 (C) Dos Reis & DaCamara; CppCon 2021Headers vs header units vs named modules #include int main() { std::cout << "Hello, World!\n"; } (C) Dos Reis & DaCamara; CppCon 2021Headers vs header units vs named modules #include needed headers import needed headers import std #include “all_std

LBB0_5: # in Loop: Header=BB0_2 Depth=1 inc r11 add r10, rax add r8, r9 add rdx, rcx cmp r11, rdi je .LBB0_6 .LBB0_2: # =>This Loop Header: Depth=1 test add r9, r8 add r10, rdx cmp r11, rax je .LBB0_6 .LBB0_2: # =>This Loop Header: Depth=1 test rcx, rcx je .LBB0_5 xor ebx, ebx .LBB0_4: # Parent Loop BB0_2 shl r8, 2 shl rdx, 2 xor r11d, r11d jmp .LBB0_2 .LBB0_5: # in Loop: Header=BB0_2 Depth=1 inc r11 I’ve got bad news 33First fix idea 34 void add_blas( size_t

CLFS_LOG_BLOCK_HEADE start 0x00C0 CheckSum 0x0070 BASE_RECORD_HEADER Record[0] ... Record[n]CVE-2023-28252 Exploitation typedef struct _CLFS_LOG_BLOCK_HEADER { UCHAR MajorVersion; UCHAR MinorVersion; RecordOffsets[12]; ULONG SignaturesOffset; } CLFS_LOG_BLOCK_HEADER, *PCLFS_LOG_BLOCK_HEADER; Block Format 0x0000 CLFS_LOG_BLOCK_HEADER 0x0070 BASE_RECORD_HEADER Record[0] ... Record[n]CVE-2023-28252 Exploitation Exploitation typedef struct _CLFS_BASE_RECORD_HEADER { CLFS_METADATA_RECORD_HEADER hdrBaseRecord; CLFS_LOG_ID cidLog; ULONGLONG rgClientSymTbl[CLIENT_SYMTBL_SIZE]; ULONGLONG rgContainerSymT

illustrative example from a larger project • Project build issues • Inclusion of platform-specific header files • Concept hierarchies • Class and Function DesignOCP: The Open–Closed Principle in C++ • has its own header file to define the common definitions • The header file is responsible for including the platform-specific code • A series of preprocessor macros handles generating the header file name name to load • Example: INCLUDE_SIMD(Quat) becomes: ”Quat_SSE2.h”Header Inclusion Macros • #define INCLUDE_PLT(Feature, File) INCLUDE_BUILD_FILENAME(Feature, File) • #define INCLUDE_PLT_FEATURE(Feature)

compiled again for each translation unit — File: a.cpp #include header .hpp > // [...] — File: b.cpp #include header .hpp > // [...]10/50 Hello Modules! — File: module.cpp export module export void take_over_the_world () {} struct SecretMasterplan {} ;21/50 We’re not talking about Header Units22/50 If you want to know more... Daniela Engert - So you want to use C++ Modules... cross-platform my_executable PUBLIC ${ PROJECT_SOURCE_DIR }/ my_src.cpp ${ PROJECT_SOURCE_DIR }/inc/my_header1.hpp ${ PROJECT_SOURCE_DIR }/inc/my_header2.hpp ) target_include_directories ( my_executable PUBLIC ${ PROJECT_SOURCE_DIR

. . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 13 Howtos 183 13.1 How to package header-only libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 13.2 How generated. By the way, “binary package” is in quotes because, strictly, it is not necessarily a binary. A header-only library, for example, will contain just the headers in the “binary package”. All the binary configuration. Static or shared library are not settings that apply to all packages. Some can be header only libraries while others packages can be just data, or package executables. Packages can contain

. . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 13 Howtos 181 13.1 How to package header-only libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 13.2 How generated. By the way, “binary package” is in quotes because, strictly, it is not necessarily a binary. A header-only library, for example, will contain just the headers in the “binary package”. All the binary configuration. Static or shared library are not settings that apply to all packages. Some can be header only libraries while others packages can be just data, or package executables. Packages can contain