Digital UNIX Calling Standard for Alpha Systems

This document, intended for compiler and debugger implementers, defines the procedure calling standard for Digital UNIX on Alpha systems. It establishes the requirements, conventions, and mechanisms—including register usage, stack frame organization, and flow control—that enable interoperability for native user-mode procedures in a multilanguage and multithreaded environment. The standard details the structures for procedure descriptors, which facilitate stack tracing and exception handling, and defines how data is passed and returned between procedures. Additionally, it addresses event processing, unwinding mechanisms, and requirements for stack limit checking in multithreaded environments.