GNU Autotools

src/main.c

#include <config.h>
#include <stdio.h>

int main(void)
{
    puts ("Hello World!");
    puts ("This is " PACKAGE_STRING ".");
    return 0;
}

configure.ac

AC_INIT([amhello], [1.0], [bug-report@address])
AM_INIT_AUTOMAKE([foreign -Wall -Werror])
AC_PROG_CC
AC_CONFIG_HEADER([config.h])
AC_CONFIG_FILES([Makefile src/Makefile])
AC_OUTPUT

Makefile.am

SUBDIRS = src

src/Makefile.am

bin_PROGRAMS = hello
hello_SOURCES = main.c

此时的文件结构为(ls -R):

.:
Makefile.am  configure.ac  src

src:
Makefile.am  main.c

$: autoreconf --install
configure.ac:2: installing `./install-sh'
configure.ac:2: installing `./missing'
src/Makefile.am: installing `./depcomp'

此时的文件结构为(ls -R):

.:
Makefile.am  aclocal.m4      config.h.in  configure.ac  install-sh  src
Makefile.in  autom4te.cache  configure    depcomp       missing

autom4te.cache:
output.0  output.1  requests  traces.0  traces.1

src:
Makefile.am  Makefile.in  main.c

• Makefile.in config.h.in configure* src/Makefile.in : expected configuration templates.
• aclocal.m4 : denitions for third-party macros used in configure.ac.
• depcomp* install-sh* missing* : auxiliary tools used during the build.
• autom4te.cache/ autom4te.cache/* : Autotools cache files

checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... /bin/mkdir -p
checking for gawk... gawk
checking whether make sets $(MAKE)... yes
checking for gcc... gcc
...
configure: creating ./config.status
config.status: creating Makefile
config.status: creating src/Makefile
config.status: creating config.h
config.status: executing depfiles commands

/usr/bin/make  all-recursive
make[1]: Entering directory `/home/zhangjie/TempFile/src'
Making all in src
make[2]: Entering directory `/home/zhangjie/TempFile/src/src'
gcc -DHAVE_CONFIG_H -I. -I..     -g -O2 -MT main.o -MD -MP -MF .deps/main.Tpo -c -o main.o main.c
mv -f .deps/main.Tpo .deps/main.Po
gcc  -g -O2   -o hello main.o
make[2]: Leaving directory `/home/zhangjie/TempFile/src/src'
make[2]: Entering directory `/home/zhangjie/TempFile/src'
make[2]: Leaving directory `/home/zhangjie/TempFile/src'
make[1]: Leaving directory `/home/zhangjie/TempFile/src'

$: src/hello
Hello World!
This is amhello 1.0.

$: make distcheck
...
=============================================
amhello-1.0 archives ready for distribution:
amhello-1.0.tar.gz
=============================================

$ tar ztf amhello-1.0.tar.gz
amhello-1.0/
amhello-1.0/Makefile.am
amhello-1.0/aclocal.m4
amhello-1.0/configure.ac
amhello-1.0/src/
amhello-1.0/src/Makefile.am
amhello-1.0/src/main.c
amhello-1.0/src/Makefile.in
amhello-1.0/config.h.in
amhello-1.0/Makefile.in
amhello-1.0/missing
amhello-1.0/configure
amhello-1.0/depcomp
amhello-1.0/install-sh

• autoconf : Create configure from configure.ac .
• autoheader : Create config.h.in from configure.ac .
• autoreconf : Run all tools in the right order.
• autoscan : Scan sources for common portability problems, and related macros missing from configure.ac .
• autoupdate : Update obsolete macros in configure.ac .
• ifnames : Gather identiers from all #if/#ifdef/... directives.
• autom4te : The heart of Autoconf. It drives M4 and implements the features used by most of the above tools. Useful for creating more than just configure files.

• automake : Create Makefile.in/s from /Makefile.am/s and /configure.ac .
• aclocal : Scan configure.ac for uses of third-party macros, and gather denitions in aclocal.m4.

在实际应用中:

• 没必要记住所有工具之间的关系；
• 在初始化的时候，使用 =autoreconf –install=；
• 修改输出(配置)文件的时候，重建规则；
• 你需对解每个工具产生的错误都有一个粗糙的理解（至少要知道是谁产生的错误）。

AC_INIT([amhello], [1.0], [bug-report@address])
AM_INIT_AUTOMAKE([foreign -Wall -Werror])
AC_PROG_CC
AC_CONFIG_HEADER([config.h])
AC_CONFIG_FILES([Makefile src/Makefile])
AC_OUTPUT

• AC_INIT: Initialize Autoconf. Specify package's name, version number, and bug-report address.
• AM_INIT_AUTOMAKE: Initialize Automake. Turn on all Automake warnning and report them as errors. This is a foreign package.
• AC_PROG_CC: Check for a C compiler.
• AC_CONFIG_HEADER([config.h]): Declare config.h as output header.
• AC_CONFIG_FILES: Declare Makefile and src/Makefile as output files.
• AC_OUTPUT: Actually output all declared files.

SUBDIRS = src

• Build recursively in src/ .
• Nothing else is declared for the current directory.(The top-level Makefile.am is usually short.)

bin_PROGRAMS = hello
hello_SOURCES = main.c

• We are building some programs.
• These programs will be installed in bindir (注意看下面tip的结构).
• There is only one program to build: hello.
• To create hello, just compile main.c.

tip: Standard File System Hierarchy:

• "autoconf is a macro processor.
• It converts configure.ac, which is a shell script using macro instructions, into congfiure, a full-fledged shell script.
• Autoconf offers many macros to perform common conguration checks.
• It is not uncommon to have a configure.ac without shell construct, using only macros.
• While processing configure.ac it is also possible to trace the occurrences of macros. This is how "autoheader" creates config.h.in . It just looks for the macros that #define symbols.
• The real macro processor actually is GNU M4. Autoconf offers some infrastructure on top of that, plus the pool of macros.

exmple.m4:

m4_define(NAME1, Harry)
m4_define(NAME2, Sally)
m4_define(MET, $1 met $2)
MET(NAME1, NAME2)

output:

$: m4 -P example.m4
# 空白
# 空白
# 空白
Harry met Sally

M4 是一个宏处理器，将输出拷贝到输出。可以内嵌，也可以用户自定义，除了宏展开以外，M4还有一些内建的函数，用来引用文件、执行Unix命令、文本操作、循环等。

这里不详细展开表述 M4，但是要记住 M4 是 Autoconf 的核心，Autoconf 只是封装了一些指令而已。

• 在许多机器上， Auto = M4，和一些预定义的宏。
• 引用是 [ 和 ] (而不是 ' 和 ')。

• 也因此在 Shell 中做比较使用 test ，而不是 [ 。

  if test "$x" = "$y"; then ...
  

• 使用 AC_DEFUN 定义宏。

  AC_DEFUN([NAME1], [Harry, Jr.])
  AC_DEFUN([NAME2], [Sally])
  AC_DEFUN([MET], [$1 met $2])
  MET([NAME1], [NAME2])
  

# Prelude
AC_INIT([PACKAGE], [VERSION], [BUG-REPORT-ADDRESS])
AM_INIT_AUTOMAKE([foreign -Wall -Werror])
AC_PREREQ(VERSION) #  Eg. AC_PREREQ([2.65])
AC_CONFIG_SRCDIR(FILE) # Eg. AC_CONFIG_SRCDIR([src/main.c])
AC_CONFIG_AUX_DIR(DIRECTORY) # mising, install-sh 等临时文件的目录 eg. AC_CONFIG_AUX_DIR([build-aux])

# Checks for programs.
AC_PROG_CC
AC_PROG_CXX
AC_PROG_AWK
AC_CHECK_PROGS(VAR, PROGS, [VAL-IF-NOT-FOUND]) # Dene VAR to the rst PROGS found, or to VAL-IF-NOT-FOUND otherwise.

# Check for libraries.
AC_CHECK_LIB(LIBRARY, FUNCT, [ACT-IF-FOUND], [ACT-IF-NOT]) # Check whether LIBRARY exists and contains FUNCT. AC CHECK HEADERS(HEADERS...)Execute ACT-IF-FOUND if it does, ACT-IF-NOT otherwise

# Check for header files.
AC_CHECK_HEADERS(HEADERS...) # Check for HEADERS and #define HAVE_HEADER_H for each header found. eg. AC_CHECK_HEADERS([sys/param.h unistd.h])

# Check for typedefs, structures, and compiler characteristics.

# Check for library functions.

# Output files.
AC_CONFIG_HEADERS([config.h])
AC_CONFIG_FILES([Makefile src/Makefile ...])
AC_OUTPUT

• Automake helps creating portable and *GNU-standard compliant /Makefile/s.
  • You may be used to other kinds of build systems.(eg. no VPATH builds, but all objects go into obj/).
  • Do not use Automake if you do not like the GNU Build System: Automake will get in your way if you don't fit the mold.
• "automake" creates complex /Makefile.in/s from simple /Makefile.am/s.
  • Consider /Makefile.in/s as internal details.
• /Makele.am/s follow roughly the same syntax as /Makefile/s however they usually contains only variable denitions.
  • "automake"" creates build rules from these definitions.
  • It's OK to add extra Makefile rules in Makefile.am: "automake" will preserve them in the output.

语法: AM_INIT_AUTOMAKE([OPTIONS...])]) . eg: AM_INIT_AUTOMAKE([foreign -Wall -Werror]) .

选项:

• -Wall : 关闭所有警告.
• -Werror : 把警告当成错误.
• foreign : 放宽 GNU 标准要求.
• 1.11.1 : automake 的最小版本号
• dist-bzip2 : Also create tar.bz2 archives during make dist and make distcheck.
• tar-ustar : Create tar archives using the ustar format.

AC_CONFIG_FILES(FILES...) : Automake 为每一个有 FILE.am 的 FILE 生成一个 FILE.in 文件。

eg: AC_CONFIG_FILES([Makefile sub/Makefile]) 会生成 Makefile.am 和 sub/Makefile.am.

bin_PROGRAMS = foo run-me
foo_SOURCES = foo.c foo.h print.c print.h
run_me_SOURCES = run.c run.h print.c

• These programs will be installed in $(bindir).
• The sources of each program go into /program/_SOURCES.
• Non-alphanumeric characters are mapped to '_'.
• Automake automatically computes the list of objects to build and link from these files.
• Header files are not compiled. We list them only so they get distributed (Automake does not distribute files it does not know about).
• It's OK to use the same source for two programs.
• Compiler and linker are inferred from the extensions.

lib_LIBRARIES = libfoo.a libbar.a
libfoo_a_SOURCES = foo.c privfoo.h
libbar_a_SOURCES = bar.c privbar.h
include_HEADERS = foo.h bar.h

• These libraries will be installed in $(libdir).
• Library names must match lib*.a.
• Public headers will be installed in $(includedir).
• Private headers are not installed, like ordinary source files.

• 在每个目录下都要有一个 Makefile (也就是 Makefile.am)。

• 所有的 Makefile 都要在 configure.ac 中声明.

  AC_CONFIG_FILES([Makefile lib/Makefile src/Makefile src/dira/Makefile src/dirb/Makefile])
  

• 在顶层目录下运行 make.

• Makefile.am/s should fix the order in which to recurse directories using the /SUBDIRS variable.

  file: Makefile.am
  SUBDIRS = lib src
  

• The current directory is implicitly built after subdirectories.
• You can put: .' where you want to override this.

• Remember VPATH builds: a source file is not necessary in the current directory.
• There are two twin trees: the build tree, and the source tree.
• Makefile and objects files are in the build tree.
• Makefile.in, Makefile.am, and source files are in the source tree.
• If ./configure is run in the current directory, the two trees are one.
• In each Makefile, 'config.status' will define $(srcdir): the path to the matching source directory.
• When referring to sources files or targets in Automake variables, you do not have to worry about source vs. build, because 'make' will check both directories.
• You may need $(srcdir) when specifying flags for tools, or writing custom commands. E.g., to tell the compiler to include headers from dir/ , you should write -I$(srcdir)/dir, not -Idir. (-Idir would fetch headers from the build tree.)

lib/Makefile.am:

noinst_LIBRARIES = libcompat.a
libcompat_a_SOURCES = xalloc.c xalloc.h

src/Makefile.am:

bin_PROGRAMS = foo run-me
foo_SOURCES = foo.c foo.h print.c print.h
run_me_SOURCES = run.c run.h print.c
run_me_LDADD = ../lib/libcompat.a
run_me_CPPFLAGS = -I$(srcdir)/../lib

• This is a convenience library, used only when building the package.
• LDADD is added when linking all programs.
• AM_CPPFLAGS contains additional preprocessor flags.
• You can use per-target variables: they apply to a single program

Assuming foo is a program or library:

• foo_CFLAGS : Additional C compiler flags.
• foo_CPPFLAGS : Additional preprocessor flags (-Is and -Ds).
• foo_LDADD : Additional link objects, -ls and -Ls (if foo is a program).
• foo_LIBADD : Additional link objects, -ls and -Ls (if foo is a library).
• foo_LDFLAGS : Additional linker flags.

The default value for foo_XXXFLAGS is $(AM_XXXFLAGS).

Use plain file names to refer to libraries inside your package (keep -ls and -Ls for external libraries only).

src/Makefile.am:

bin_PROGRAMS = foo run-me
foo_SOURCES = foo.c foo.h print.c print.h
run_me_SOURCES = run.c run.h print.c
run_me_CPPFLAGS = -I$(srcdir)/../lib
run_me_LDADD = ../lib/libcompat.a $(EFENCELIB)

make dist and make distcheck create a tarball containing:

• All sources declared using … SOURCES
• All headers declared using … HEADERS
• All scripts declared with dist … SCRIPTS
• All data les declared with dist … DATA
• …
• Common les such as ChangeLog, NEWS, etc.
• See automake --help for a list of those files.
• Extra les or directories listed into EXTRA_DIST.

略。