libc++

LLVM libc++, specifically for Android, removing exception and RTTI support.

Source code is extracted from both the AOSP llvm-project repository.

Minimal Header-Only Architecture

Magisk uses a minimal build setup for libc++ to keep native binary sizes small and compilation fast:

• Header-Only STL: Standard template features (std::vector, std::map, std::span, std::unique_ptr, std::atomic, std::function, etc.) are included header-only from include/.
• abi.cpp: A single 100% self-contained ABI source file that replaces libc++abi and libc++ runtime libraries, providing:
  • Weak global operator new and operator delete overloads
  • Itanium C++ ABI runtime stubs (__cxa_guard_*, __cxa_pure_virtual, __cxa_thread_atexit)
  • Core STL abort/throw helpers (std::terminate(), std::__throw_runtime_error(), std::__throw_system_error(), etc.)
  • Explicit template instantiations for std::basic_string<char> methods (required by libc++'s extern template declarations) and string conversion functions (std::to_string)
• Exported Flags: Android.mk automatically exports -fno-exceptions and -fno-rtti to all dependent modules via LOCAL_EXPORT_CFLAGS and LOCAL_EXPORT_CPPFLAGS.

Subsystem Limitations

Because out-of-line C++ runtime library code is omitted in favor of abi.cpp, standard C++ library subsystems requiring compiled runtime support are not available:

• <filesystem>: Path manipulation, directory iterators, and status operations.
• <regex>: Regular expression parsing, searching, and collate facets.
• Threading & Concurrency (<thread>, <future>, <condition_variable>, <barrier>, <latch>, <semaphore>, <stop_token>): Thread creation, async futures, and condition variable notifications. (Note: primitive std::mutex is supported via abi.cpp).
• Locales & Encoding (<locale>, <codecvt>): Global locales, formatting facets, and character conversions.
• <valarray>, <any>: Non-template helpers and type info routines.