POSIXABI

POSIXABI is a term used to describe the binary interface conventions commonly observed on POSIX-compliant operating systems. It refers to the set of platform-dependent rules that allow executables and shared libraries to interoperate at the machine level.

Core components include calling conventions, data representation and alignment, endianness, name mangling, and the interfaces used for dynamic linking with the system C library and the kernel (for example, system call conventions).

POSIXABI varies by architecture and operating system. On x86-64, many systems follow a System V-like AMD64 ABI, while ARM platforms adhere to ARM EABI variants. The POSIX API itself remains fixed while the binary interface adapts to the platform.

In development and deployment, compilers (such as GCC and Clang) target the POSIXABI of the target machine, and linkers and loaders enforce ABI compatibility when producing or loading binaries and shared libraries. Cross-compilers provide POSIXABI targets for different architectures.

POSIXABI is not a single formal standard; POSIX defines APIs, while ABIs define binary-level conventions. The term is used as a practical umbrella to discuss cross-platform binary compatibility within POSIX-like environments.

See also POSIX, ABI, System V ABI, ELF, dynamic linker, libc.