Tru64 UNIX

This document, the "Tru64 UNIX Calling Standard for Alpha Systems" (August 2000, Version 5.1 or higher), defines the requirements, mechanisms, and conventions for procedure calls within the Tru64 UNIX interface on Alpha systems.

Key aspects covered include:

• Fundamental Concepts: Address and procedure representation, register usage conventions (integer and floating-point registers), and program image layout.
• Flow Control: Different procedure types (stack frame, register frame, null frame), call conventions, linkage, and detailed entry and exit code sequences.
• Data Manipulation: Mechanisms for passing arguments (immediate value, reference, descriptor), argument list structures, data allocation, and return value handling.
• Event Processing: Comprehensive details on exception handling (types, records, handlers, raising, unwinding, signal coexistence) and stack unwinding operations.
• Multithreaded Environments: Considerations for stack limits and overflow handling.
• Procedure Invocations and Descriptors: Routines for referencing, providing context for, and walking the call chain, as well as the structure and use of procedure descriptors for run-time generated code and exception handling.

The standard aims to ensure performance, portability, efficiency, and consistency for native user-mode procedures operating in multilanguage and multithreaded Tru64 UNIX environments on Alpha hardware. It is primarily intended for compiler and debugger writers, but is relevant for all programmers dealing with procedure calling.