Class 30: Make, Revisited

Held: Monday, 25 October 2010

Summary: We consider more details of make, a useful tool for automating lots of stuff.

Related Pages:

• EBoard.
• Reading: Managing Projects with GNU Make, Chapters 1 and 2..

Notes:

• I hope you had a great break.
• Returned: HW5, Exam 1. Sorry for the delay.
• I got more responses for today's reading. Thanks. Some of you asked enough questions that I probably did not need everyone's.
• Reading for Tuesday: K&R 5.1 and 5.2.
• Are there questions on Assignment 6?

Overview:

• About Make.
• Your Questions.
• A Collaborative Makefile.

Make

• Purpose: Make it easier to build projects, particularly complex multi-part projects.
• Model: A collection of targets
  • Each target is something that we might want to build (or a placeholder to help us build stuff)
  • There are instructions for building each target.
• Typical targets:
  • default: The default thing or things to build (e.g., the application or library)
  • test or check: Instructions for testing the main thing. (Generally predicated on building default first.)
  • install: Install the things we've just built.
  • clean: Remove intermediate files (such as .o files).
  • package: Put everything together into a tarball.
• Variables: Making it easier. Four kinds:
  • Your variables
  • Standard variables you set
  • Variables from the standard rules
  • Automatic variables
• Your variables

  NAME = VALUES
  

• Standard variables you set
  • CFLAGS
  • LDFLAGS
  • LDLIBS
• Variables from the standard rules
  • $(CC)
  • $(COMPILE.c)
  • ...
• Automatic variables
  • $@ - The target
  • $< - The first prereq
  • $? - Newer prereqs
  • $^ - All prereqs
  • $* - The stem of the target

Your Questions

• Is make basically a new language we need to learn?

• I need some review of what .o files are for.
• I don't know what -I does, exactly.
• Generally, I don't understand most of this stuff about libraries. Why are they necessary?
• Can we talk a bit more about CFLAGS and similar things?

• What is a 'jar'?
• Is a lexer a program that is assumed to be built for the implementation of this program, or is it some automatic file that is generated, or what?
• What does flex do?
• What does this mean: First, we setup our experiment by creating an empty yacc source file and registering with RCSusing ci (that is, we want a version-controlled yacc source file)
• What is bison and what does it do?
• Does the suffix .y signify anything specific?
• What is an 'awk' filter?

• I still don't quite understand $(...)
• I noticed that the text used a "rm" command in the makefile - does this mean we can use any valid terminal command in our makefile rules?
• I'm a little bit confused about phony targets, though. Because they don't represent files, are phony targets kind of like functions?
• I was wondering if you might be able to show us how to use wildcards in our makefiles.
• How does this work?

  prog: *.c
          $(CC) -o $@ $^
  

Exercise

• We'll work together to build a nice Makefile for homework 5.