Page 215 - DCAP507_SYSTEM_SOFTWARE

Nisha Sethi, Lovely Professional University Unit 14: Canonic Systems

Unit 14: Canonic Systems Notes

CONTENTS
Objectives

Introduction
14.1 Syntax Specification
14.2 Specification Translation
14.3 Canonic Recognition
14.3.1 Benefits
14.4 Canonic Translation Algorithm
14.5 Canonic Systems and Formal Systems
14.6 Summary
14.7 Keywords

14.8 Review Questions
14.9 Further Readings

Objectives

After studying this unit, you will be able to:
 Scan canonic systems
 Describe syntax specification

 Demonstrate specification of translation
 Explain recognition and translation algorithm
 Discuss canonic systems and formal systems
Introduction

When using autoconf, there are three system definitions (or machine definitions) that are used
to identify the "actors" in the build process; each definition relates to a similarly-named variable.
These three definitions are:
 host (CHOST): The system that is going to run the software once it is built, which is the
main actor. Once the software has been built, it will execute on this particular system.
 build (CBUILD): The system where the build process is being executed. For most uses this
would be the same as the host system, but in case of cross-compilation the two obviously
differ.

 target (CTARGET): The system against which the software being built will run on. This
actor only exists, or rather has a meaning, when the software being built may interact
specifically with a system that differs from the one it's being executed on (our host). This
is the case for compilers, debuggers, profilers and analyzers and other tools in general.
To identify the current actors involved in the build process, autoconf provides three macros that
take care of finding the so-called "canonic" values: AC_CANONIC_HOST, AC_CANONIC_BUILD
and AC_CANONIC_TARGET. These three macros then provide to the configure script the
variables with the name of the actor ($host, $build and $target), and three parameters with the
same name to the configure script so that the user can override the default discovered values.

LOVELY PROFESSIONAL UNIVERSITY 209