Steps to use autoconf to generate Makefile and compile the project

Preface

Under Linux, compilation and linking require the use of Makefile, but writing a good Makefile is not easy, and writing a standard Makefile is even more troublesome. We can use autoconf to generate a Makefile, which can save a lot of trouble, especially in large projects.

Here I will use a project to illustrate how to do it. Some steps are not required, but if you can't tell which steps are not required, it's best to follow them step by step, because some steps are omitted and the code also needs to be modified accordingly (such as modifying the path, etc.).

step

First install autoconf

sudo apt-get install autoconf

Create a new project folder (for example: joy)

mkdir joy

cd joy

Create two new folders lib and src in it to store the library files and source files of the project.

mkdir lib

mkdir src

As shown in the following figure:

Enter the lib folder, create a new header file, such as haha.h, and declare a function at random.

cd lib

gedit haha.h

//haha.h
#include <stdio.h>
void printhaha();

Enter the src folder, create a new C file, such as haha.c, to implement the functions of the header file; create a new C file, such as main_code.c, to write the main function.

cd ../src

gedit haha.c

//haha.c
#include "../lib/haha.h"
void printhaha()
{
  printf("haha\n");
}

//main_code.c
#include "../lib/haha.h"
void main()
{
  printhaha();
}

Back to the joy folder, our project files have been written

cd ..

Run autoscan to generate configure.scan

autoscan

Edit configure.scan

gedit configure.scan

The file before editing is like this

#Edit the original file before# -*- Autoconf -*-
# Process this file with autoconf to produce a configure script.
AC_PREREQ([2.69])
AC_INIT([FULL-PACKAGE-NAME], [VERSION], [BUG-REPORT-ADDRESS])
AC_CONFIG_SRCDIR([src/haha.c])
AC_CONFIG_HEADERS([config.h])
# Checks for programs.
AC_PROG_CC
# Checks for libraries.
# Checks for header files.
# Checks for typedefs, structures, and compiler characteristics.
# Checks for library functions.
AC_OUTPUT

The prefix AC refers to AutoConf
Don't worry about AC_PREREQ
Fill in [package name] [version] [bug submission address (that is, your email address)] in AC_INIT
Fill in any file name under the source file path in AC_CONFIG_SRCDIR. Autoconf will determine whether the path is correct by checking whether the file exists. Generally, you don't need to worry about it.
Don't worry about inserting the following sentence into AC_CONFIG_HEADERS. It is required in the automake stage, otherwise an error will be reported.
AM_INIT_AUTOMAKE
The prefix AM refers to AutoMake
The last AC_OUTPUT is changed to AC_OUTPUT (Makefile)
The modified file looks like this:

#Modified Files# -*- Autoconf -*-
# Process this file with autoconf to produce a configure script.
AC_PREREQ([2.69])
AC_INIT(hhh, 1.0, [email protected])
AC_CONFIG_SRCDIR([src/haha.c])
AC_CONFIG_HEADERS([config.h])
AM_INIT_AUTOMAKE  
# Checks for programs.
AC_PROG_CC
# Checks for libraries.
# Checks for header files.
# Checks for typedefs, structures, and compiler characteristics.
# Checks for library functions.
AC_OUTPUT(Makefile)

Save and rename configure.scan to configure.ac

Create a new Makefile.am

gedit Makefile.am

Enter the following code

AUTOMAKE_OPTIONS= \
  foreign \
  subdir-objects
bin_PROGRAMS=test_prj 
test_prj_SOURCES= \
  lib/haha.h \
  src/haha.c \
  src/main_code.c

AUTOMAKE_OPTIONS is followed by automake execution options, separated by spaces;
foreign means only necessary files are detected;
subdir-objects means that the compiled .o files can be placed in the sub-path (together with the source files). Without this option, all .o files will be placed in the project root directory;
The name after bin_PROGRAMS is the name of the generated executable binary file. There can be multiple bin_PROGRAMS, but each bin_PROGRAMS needs to have a corresponding xxx_SOURCES;
xxx_SOURCES is the dependencies of the executable file xxx, including header files, source files, etc.

Generate aclocal.m4 file using aclocal

aclocal

Generate configure file with autoconf

autoconf

Generate config.h.in with autoheader

autoheader

To generate Makefile.in with automake, you need to add --add-missing to automatically add the default file

automake --add-missing

Then our software is ready, and we can upload the entire package to github or an open source forum.

How do others compile and link executable files after downloading our source code package? Or how do we compile and link our executable files?

The following are the general steps for source code installation, which are also the steps for our compilation and linking

First generate the Makefile

./configure

Then make

make

Now we can see that the executable file test_prj has been generated

Run it and the results are as follows:

The result is correct.

Entering the src directory, we found two more files

This is the role of subdir-objects in AUTOMAKE_OPTIONS. Without this sentence, the two .o files will appear in your root directory. If unfortunately your project is large and there are files with the same name, there may be serious consequences, so it is recommended to add this sentence.

Summarize

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