Calling Standard for Alpha Systems

Product Version: Digital UNIX Version 4.0 or higher March 1996

This manual defines the requirements, mechanisms, and conventions used in the Digital UNIX interface that supports procedure calls for Digital UNIX on Alpha systems.

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About This Manual

This manual defines the requirements, mechanisms, and conventions used in the Digital UNIX (R) interface that supports procedure calls for Digital UNIX for Alpha systems. The standard defines the data structures, constants, algorithms, conventions, methods, and functional interfaces that enable a native user-mode procedure to operate correctly in a multilanguage and multithreaded environment on Digital UNIX systems operating on Alpha hardware.

Audience

Although this manual primarily defines requirements for compiler and debugger writers, the information applies to procedure calling for all programmers at all levels of programming.

Organization

This document includes eight chapters:

Chapter 1	Introduces the standard and provides definitions of terms used in the standard.
Chapter 2	Describes the fundamental concepts of the Digital UNIX calling standard for Alpha systems.
Chapter 3	Describes the aspects of the standard that deal with flow control.
Chapter 4	Discusses the passing and storage of data.
Chapter 5	Discusses how the standard relates to events outside the normal program flow.
Chapter 6	Discusses stack limit checking in multithreaded execution environments.
Chapter 7	Describes the mechanisms for functions that are needed to support procedure call tracing.
Chapter 8	Discusses procedure descriptors.

Related Documents

This Digital UNIX calling standard is a component of the larger Alpha Software Architecture and depends on standards and conventions not described in this document. These standards include:

Object language (including link-time optimizations) and object file format
Status values and message definition, formatting, and reporting
Heap memory management and dynamic string management
Multithread architecture
Names and naming conventions

The following documents contain information related to this standard and the standards mentioned in the previous list:

Alpha Architecture Reference Manual
Digital UNIX Programmer's Guide
Digital UNIX Assembly Language Programmer's Guide
Guide to DECthreads
Digital Portable Mathematics Library
Digital UNIX POSIX Conformance Document
Information Technology - Portable Operating System Interface (POSIX) - Part 1: System Application Program Interface (API) [C Language] ISO/IEC 9945-1: 1990
American National Standard for Information Systems Programming Language C - ANSI X3.159-1989 and its international equivalent, ISO/IEC 9899

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Conventions

This document uses the following typographical and symbol conventions:

%
$: A percent sign represents the C shell system prompt. A dollar sign represents the system prompt for the Bourne and Korn shells.
% cat: Boldface type in interactive examples indicates typed user input.
file: Italic (slanted) type indicates variable values, placeholders, and function argument names.
[|]
{|}: In syntax definitions, brackets indicate items that are optional and braces indicate items that are required. Vertical bars separating items inside brackets or braces indicate that you choose one item from among those listed.
cat(1): A cross-reference to a reference page includes the appropriate section number in parentheses. For example, cat(1) indicates that you can find information on the cat command in Section 1 of the reference pages.

The following presentation conventions apply to this standard:

Constants, data structures, and functional interfaces
Constants are represented symbolically with their values given at the point of definition in the standard. Data structures are defined in terms of the physical memory format of each structure. Functional interface syntax is presented in abstract form. Concrete language bindings for each constant, data structure, and functional interface are provided in system definition files external to the standard.
Algorithms
Algorithms are presented as a series of steps in standard American English.
Numbering
All numbers are represented as decimal values unless otherwise indicated. Nondecimal numbers are represented with the base name in parentheses following the number, for example, 1B(hex).
Memory and register layouts
Figures that represent memory or register layouts follow the convention that increasing addresses run from top to bottom and right to left. The most significant bits are on the left; the least significant bits are on the right.
Code examples
All code examples are supplied to clarify the concept under discussion. These examples do not necessarily reflect the optimized or properly scheduled code sequences that a compiler would generate. The assembly language syntax follows the conventions used in the Digital UNIX Assembly Language Programmer's Guide.
Record fields
Record fields are referred to by using the name of the record or subrecord followed by a dot (\.) and then the field name:
record-name.subrecord-name.field