configure.ac_linux中configure报错_configure prefix

GCC使用configure.ac（通过autoconf）来生成configure文件。configure.ac顶层目录下的configure.ac有三千多行，用来在配置阶段做各种测试检测，并将结果替换到Makefile.in中，生成最终的Makefile。本文简单介绍了configure.ac中所要做的事请，并没有覆盖所有的细节问题。

1、导出原始的configure参数

progname=$0
# if PWD already has a value, it is probably wrong.
if test -n "$PWD" ; then PWD=`${PWDCMD-pwd}`; fi

# Export original configure arguments for use by sub-configures.
# Quote arguments with shell meta charatcers.
TOPLEVEL_CONFIGURE_ARGUMENTS=
set -- "$progname" "$@"
for ac_arg
do
  case "$ac_arg" in
  *" "*|*"      "*|*[[\[\]\~\#\$\^\&\*\(\)\{\}\\\|\;\<\>\?\']]*)
    ac_arg=`echo "$ac_arg" | sed "s/'/'\\\\\\\\''/g"`
    # if the argument is of the form -foo=baz, quote the baz part only
    ac_arg=`echo "'$ac_arg'" | sed "s/^'\([[-a-zA-Z0-9]]*=\)/\\1'/"` ;;
  *) ;;
  esac
  # Add the quoted argument to the list.
  TOPLEVEL_CONFIGURE_ARGUMENTS="$TOPLEVEL_CONFIGURE_ARGUMENTS $ac_arg"
done
if test "$silent" = yes; then
  TOPLEVEL_CONFIGURE_ARGUMENTS="$TOPLEVEL_CONFIGURE_ARGUMENTS --silent"
fi
# Remove the initial space we just introduced and, as these will be
# expanded by make, quote '$'.
TOPLEVEL_CONFIGURE_ARGUMENTS=`echo "x$TOPLEVEL_CONFIGURE_ARGUMENTS" | sed -e 's/^x *//' -e 's,\\$,$$,g'`
AC_SUBST(TOPLEVEL_CONFIGURE_ARGUMENTS)

这部分代码位于38-64行，用来将configure的参数保存到变量TOPLEVEL_CONFIGURE_ARGUMENTS中，以供子目录的configure使用。

2、一些基本的测试

# Find the build, host, and target systems.
ACX_NONCANONICAL_BUILD
ACX_NONCANONICAL_HOST
ACX_NONCANONICAL_TARGET
... ...
AC_CANONICAL_SYSTEM
AC_ARG_PROGRAM

m4_pattern_allow([^AS_FOR_TARGET$])dnl
m4_pattern_allow([^AS_FOR_BUILD$])dnl

# Get 'install' or 'install-sh' and its variants.
AC_PROG_INSTALL
ACX_PROG_LN
AC_PROG_LN_S
AC_PROG_SED
AC_PROG_AWK
...

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