The ftp server The The dnsresolver
4.2.4 Explicit Rules
There are two types of rules: explicit rules and implicit rules. All of the rules that we have been using in this chapter until now are explicit rules. An explicit rule has three parts: target, dependencies and commands. Explicit rules are defined in detail and they perform exactly as they are written. In general, all rules present in a makefile are explicit rules.4.2.5 Implicit Rules
Implicit rules are used by make to build certain targets by itself. These rules are usually language-specific and operate depending upon file extension. For example, make can build .o files from .c files using an implicit rule for C language compilation. Consider the basic make- file we used earlier in this chapter as shown below: Variable definition OBJS = ftp.o common.o HDRS = ftp.h common.h CFLAGS = -g -O2 TARGETS = ftp CC = gcc Default Target ftp: OBJS HDRS CC OBJS -o ftp ftp.o: ftp.c HDRS CC CFLAGS -c ftp.c common.o: common.c common.h CC CFLAGS -c common.c clean: rm -f TARGETS OBJS Using Variables 119 You can modify this file so that it uses implicit rules to build object files. The modified file is shown below: Variable definition OBJS = ftp.o common.o HDRS = ftp.h common.h CFLAGS = -g -O2 TARGETS = ftp CC = gcc Default Target ftp: OBJS HDRS CC OBJS -o ftp clean: rm -f TARGETS OBJS Note that we have completely taken out two rules that are used to build the object files. Now when make needs to build these object files, it uses its implicit rule for this purpose. Run- ning make on this makefile produces the following result. [rootconformix make] make gcc -g -O2 -c -o ftp.o ftp.c gcc -g -O2 -c -o common.o common.c gcc ftp.o common.o -o ftp [rootconformix make] Note that the first two lines of the output create object files using implicit rules. You may also have noted that the CFLAGS variable is also used in this process. Like CFLAGS, implicit rules use other variables while building targets. For a more detailed discussion, please see the reference at the end of this chapter. While using implicit rules, you should be careful about the process, because make can build a target using explicit rule depending upon which source files are available. For example, make can produce an object file from a C source code file as well as Pascal source code file. In the above example, if common.c file is not present but common.p Pascal source code file is present in the current directory, make will invoke Pascal compiler to create common.o file, which may be wrong. You also have less control over options on implicit rules.4.3 Using Variables
Variables are an important part of all makefiles used in a project. Variables are used for many purposes; the most important of which is to have structured and easily understandable makefiles. This section contains more information about variables used in makefiles.Parts
» the linux development platform 2003
» Requirement Gathering Life Cycle of a Software Development Project
» Writing Functional Specifications Life Cycle of a Software Development Project
» Creating Architecture and Design Documents
» Implementation and Coding Life Cycle of a Software Development Project
» Testing Life Cycle of a Software Development Project
» Technical documentation developed during the development process. This includes
» Technical documentation prepared for technical support staff. This includes technical
» End-user manuals and guides. This is the documentation for the end user to assist the
» Software Releases Support and New Features
» Hardware Platform Components of a Development System
» Operating System Components of a Development System
» Editors Components of a Development System
» Compilers and Assemblers Components of a Development System
» Debuggers Components of a Development System
» Version Control Systems Components of a Development System
» Selection Criteria for Hardware Platform Selection Criteria for Software Development Tools
» Creating Deadlines Managing Development Process
» Managing the Development Team
» Resolving Dependencies Managing Development Process
» Libraries Linux Development Platform Specifications LDPS and Linux
» Open Source Developers Network at http:www.osdn.org
» Extensibility What to Look for in an Editor
» References and Resources the linux development platform 2003
» Target machine. This is the machine for which the newly built compiler will generate
» Post-Installation Tasks Installing GNU Compiler
» Compiling to Intermediate Levels
» Compilation with Debug Support
» Compilation with Optimization Compiling a Program
» Compiling Source Code for Other Languages
» Linking a program Assembling a Program
» Creating Libraries the linux development platform 2003
» Standard Libraries the linux development platform 2003
» Compiling Fortran Programs the linux development platform 2003
» Smalltalk Oberon Other Compilers
» The target 2. Dependencies Basic Terminology
» The explicit rules 2. The implicit rules
» Input Files Introduction to GNU make
» Typical Contents of a Makefile
» Running make Introduction to GNU make
» Shell to Execute Commands Include Files
» The ftp server The The dnsresolver
» FTPOBJS OBJS Another Example of Makefile
» Explicit Rules The make Rules
» Implicit Rules The make Rules
» Defining Variables Types of Variables
» Pre-Defined Variables Automatic Variables
» Makefile in The Top Directory
» Makefile in common-dir Directory
» Makefile in the ftp-dir Directory
» Makefile in the tftp-dir Directory Makefile in the dns-dir Directory
» Building Everything Working with Multiple Makefiles and Directories
» The ifdef Directive Control Structures and Directives
» The ifndef Directive Control Structures and Directives
» Compilation Getting the Latest Version and Installation
» Most Commonly Used gdb Commands
» Passing Command Line Arguments to the Program Being Debugged
» The step and finish Commands
» Introduction to GDB Working with the Stack
» Displaying Program Variables Displaying Variables
» Automatic Displaying Variables with Each Command
» Displaying Environment Variables Displaying Variables
» Modifying Variables Displaying Variables
» Disabling Break Points Enabling Break Points
» Debugging Optimized Code the linux development platform 2003
» Debugging Running Processes the linux development platform 2003
» The kdbg Debugger Other Open Source Debuggers
» The ddd Debugger Other Open Source Debuggers
» The xxgdb Debugger Other Open Source Debuggers
» CVS Policies the linux development platform 2003
» Project Management and Communication
» Remote Repositories Checking out a Project
» Finding the Status of a Project
» Finding Differences Using the CVS Client
» Resolving Conflicts Using the CVS Client
» Checking the Project Back In Adding Files to a Project
» Removing Files from a Project
» Tags and Releases Using the CVS Client
» System Requirements Introduction to jCVS
» Installation Instructions Introduction to jCVS
» Using jCVS Introduction to jCVS
» Installing pcl-cvs Using Emacs with CVS
» Using pcl-cvs Using Emacs with CVS
» Have a shell account on the CVS server. 2. Create a publicprivate key pair on the client.
» Selecting Coding Styles Using indent Utility
» Formatting Braces Using indent Utility
» Formatting Declarations Using indent Utility
» Breaking Long Lines Using indent Utility
» Summary of Options Using indent Utility
» Using sed Utility Using cscope and cbrowser
» Generating C Function Prototypes from C Source Code Using cproto
» Using ltrace and strace Utilities
» Value 2. Type Name Using the nm Utility
» Using the ranlib Utility Using the strip Utility
» Using the strings Utility Using the addr2line Utility
» Host Machine Introduction to the Cross-Platform Development Process
» Target Machine Introduction to the Cross-Platform Development Process
» Cross Platform Development Cycle
» Embedded Systems and Moving Parts
» Embedded Systems and Power Consumption
» Embedded Operating Systems What are Embedded Systems?
» Knowledge of Target System Hardware
» Software Emulators Cross Compilations
» Using gdbserver with GNU Debugger
» Attaching to a Running Process Using gdbserver
» Arcom SBC-GX1 Board Hardware Used for Cross-Platform and Embedded Systems
» Artesyn PMPPC Mezzanine Card
» References the linux development platform 2003
» Java Compiler Java Virtual Machine
» Kaffe the linux development platform 2003
» The Jboss Java Development System
» Getting and Installing Java SDK from Sun Creating jar Files
» Creating Source Code File Compiling Java Code
» Running Java Applications Building Java Applications
» Using gcj to Build Java Applications
» Building Applets the linux development platform 2003
» Testing Applets with Netscape
» Jikes for Java the linux development platform 2003
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