lang.m4

autoconf是一个产生可以自动配置源代码包

# AC_LANG_PREPROC_REQUIRE
# -----------------------
# Ensure we have a preprocessor for the current language.
AC_DEFUN([AC_LANG_PREPROC_REQUIRE],
[m4_require([AC_LANG_PREPROC(]_AC_LANG[)],
	    [AC_LANG_PREPROC])])


# AC_REQUIRE_CPP
# --------------
# Require the preprocessor for the current language.
# FIXME: AU_ALIAS once AC_LANG is officially documented (2.51?).
AC_DEFUN([AC_REQUIRE_CPP],
[AC_LANG_PREPROC_REQUIRE])



# AC_NO_EXECUTABLES
# -----------------
# FIXME: The GCC team has specific needs which the current Autoconf
# framework cannot solve elegantly.  This macro implements a dirty
# hack until Autoconf is able to provide the services its users
# need.
#
# Several of the support libraries that are often built with GCC can't
# assume the tool-chain is already capable of linking a program: the
# compiler often expects to be able to link with some of such
# libraries.
#
# In several of these libraries, workarounds have been introduced to
# avoid the AC_PROG_CC_WORKS test, that would just abort their
# configuration.  The introduction of AC_EXEEXT, enabled either by
# libtool or by CVS autoconf, have just made matters worse.
#
# Unlike an earlier version of this macro, using AC_NO_EXECUTABLES does
# not disable link tests at autoconf time, but at configure time.
# This allows AC_NO_EXECUTABLES to be invoked conditionally.
AC_DEFUN_ONCE([AC_NO_EXECUTABLES],
[m4_divert_push([KILL])
m4_divert_text([DEFAULTS], [ac_no_link=no])

AC_BEFORE([$0], [_AC_COMPILER_EXEEXT])
AC_BEFORE([$0], [AC_LINK_IFELSE])

m4_define([_AC_COMPILER_EXEEXT],
[AC_LANG_CONFTEST([AC_LANG_PROGRAM()])
if _AC_DO_VAR(ac_link); then
  ac_no_link=no
  ]m4_defn([_AC_COMPILER_EXEEXT])[
else
  ac_no_link=yes
  # Setting cross_compile will disable run tests; it will
  # also disable AC_CHECK_FILE but that's generally
  # correct if we can't link.
  cross_compiling=yes
  EXEEXT=
  _AC_COMPILER_EXEEXT_CROSS
fi
])

m4_define([AC_LINK_IFELSE],
[if test x$ac_no_link = xyes; then
  AC_MSG_ERROR([Link tests are not allowed after AC@&t@_NO_EXECUTABLES.])
fi
]m4_defn([AC_LINK_IFELSE]))

m4_divert_pop()dnl
])# AC_NO_EXECUTABLES



# ----------------------------- #
# Computing EXEEXT and OBJEXT.  #
# ----------------------------- #


# Files to ignore
# ---------------
# Ignore .d files produced by CFLAGS=-MD.
#
# On UWIN (which uses a cc wrapper for MSVC), the compiler also generates
# a .pdb file
#
# When the w32 free Borland C++ command line compiler links a program
# (conftest.exe), it also produces a file named `conftest.tds' in
# addition to `conftest.obj'.
#
# - *.bb, *.bbg
#   Created per object by GCC when given -ftest-coverage.
#
# - *.xSYM
#   Created on BeOS.  Seems to be per executable.
#
# - *.map, *.inf
#   Created by the Green Hills compiler.


# _AC_COMPILER_OBJEXT_REJECT
# --------------------------
# Case/esac pattern matching the files to be ignored when looking for
# compiled object files.
m4_define([_AC_COMPILER_OBJEXT_REJECT],
[*.$ac_ext | *.xcoff | *.tds | *.d | *.pdb | *.xSYM | *.bb | *.bbg | *.map | *.inf])


# _AC_COMPILER_EXEEXT_REJECT
# --------------------------
# Case/esac pattern matching the files to be ignored when looking for
# compiled executables.
m4_define([_AC_COMPILER_EXEEXT_REJECT],
[_AC_COMPILER_OBJEXT_REJECT | *.o | *.obj])


# We must not AU define them, because autoupdate would then remove
# them, which is right, but Automake 1.4 would remove the support for
# $(EXEEXT) etc.
# FIXME: Remove this once Automake fixed.
AC_DEFUN([AC_EXEEXT],   [])
AC_DEFUN([AC_OBJEXT],   [])


# _AC_COMPILER_EXEEXT_DEFAULT
# ---------------------------
# Check for the extension used for the default name for executables.
#
# We do this in order to find out what is the extension we must add for
# creating executables (see _AC_COMPILER_EXEEXT's comments).
#
# Beware of `expr' that may return `0' or `'.  Since this macro is
# the first one in touch with the compiler, it should also check that
# it compiles properly.
#
# On OpenVMS 7.1 system, the DEC C 5.5 compiler when called through a
# GNV (gnv.sourceforge.net) cc wrapper, produces the output file named
# `a_out.exe'.
m4_define([_AC_COMPILER_EXEEXT_DEFAULT],
[# Try to create an executable without -o first, disregard a.out.
# It will help us diagnose broken compilers, and finding out an intuition
# of exeext.
AC_MSG_CHECKING([for _AC_LANG compiler default output file name])
ac_link_default=`echo "$ac_link" | sed ['s/ -o *conftest[^ ]*//']`
#
# List of possible output files, starting from the most likely.
# The algorithm is not robust to junk in `.', hence go to wildcards (a.*)
# only as a last resort.  b.out is created by i960 compilers.
ac_files='a_out.exe a.exe conftest.exe a.out conftest a.* conftest.* b.out'
#
# The IRIX 6 linker writes into existing files which may not be
# executable, retaining their permissions.  Remove them first so a
# subsequent execution test works.
ac_rmfiles=
for ac_file in $ac_files
do
  case $ac_file in
    _AC_COMPILER_EXEEXT_REJECT ) ;;
    * ) ac_rmfiles="$ac_rmfiles $ac_file";;
  esac
done
rm -f $ac_rmfiles

AS_IF([_AC_DO_VAR(ac_link_default)],
[# Autoconf-2.13 could set the ac_cv_exeext variable to `no'.
# So ignore a value of `no', otherwise this would lead to `EXEEXT = no'
# in a Makefile.  We should not override ac_cv_exeext if it was cached,
# so that the user can short-circuit this test for compilers unknown to
# Autoconf.
for ac_file in $ac_files
do
  test -f "$ac_file" || continue
  case $ac_file in
    _AC_COMPILER_EXEEXT_REJECT )
	;;
    [[ab]].out )
	# We found the default executable, but exeext='' is most
	# certainly right.
	break;;
    *.* )
        if test "${ac_cv_exeext+set}" = set && test "$ac_cv_exeext" != no;
	then :; else
	   ac_cv_exeext=`expr "$ac_file" : ['[^.]*\(\..*\)']`
	fi
	# We set ac_cv_exeext here because the later test for it is not
	# safe: cross compilers may not add the suffix if given an `-o'
	# argument, so we may need to know it at that point already.
	# Even if this section looks crufty: it has the advantage of
	# actually working.
	break;;
    * )
	break;;
  esac
done
test "$ac_cv_exeext" = no && ac_cv_exeext=
],
      [_AC_MSG_LOG_CONFTEST
AC_MSG_FAILURE([_AC_LANG compiler cannot create executables], 77)])
ac_exeext=$ac_cv_exeext
AC_MSG_RESULT([$ac_file])
])# _AC_COMPILER_EXEEXT_DEFAULT


# _AC_COMPILER_EXEEXT_WORKS
# -------------------------
m4_define([_AC_COMPILER_EXEEXT_WORKS],
[# Check that the compiler produces executables we can run.  If not, either
# the compiler is broken, or we cross compile.
AC_MSG_CHECKING([whether the _AC_LANG compiler works])
# FIXME: These cross compiler hacks should be removed for Autoconf 3.0
# If not cross compiling, check that we can run a simple program.
if test "$cross_compiling" != yes; then
  if _AC_DO_TOKENS([./$ac_file]); then
    cross_compiling=no
  else
    if test "$cross_compiling" = maybe; then
	cross_compiling=yes
    else
	AC_MSG_FAILURE([cannot run _AC_LANG compiled programs.
If you meant to cross compile, use `--host'.])
    fi
  fi
fi
AC_MSG_RESULT([yes])
])# _AC_COMPILER_EXEEXT_WORKS


# _AC_COMPILER_EXEEXT_CROSS
# -------------------------
m4_define([_AC_COMPILER_EXEEXT_CROSS],
[# Check that the compiler produces executables we can run.  If not, either
# the compiler is broken, or we cross compile.
AC_MSG_CHECKING([whether we are cross compiling])
AC_MSG_RESULT([$cross_compiling])
])# _AC_COMPILER_EXEEXT_CROSS


# _AC_COMPILER_EXEEXT_O
# ---------------------
# Check for the extension used when `-o foo'.  Try to see if ac_cv_exeext,
# as computed by _AC_COMPILER_EXEEXT_DEFAULT is OK.
m4_define([_AC_COMPILER_EXEEXT_O],
[AC_MSG_CHECKING([for suffix of executables])
AS_IF([_AC_DO_VAR(ac_link)],
[# If both `conftest.exe' and `conftest' are `present' (well, observable)
# catch `conftest.exe'.  For instance with Cygwin, `ls conftest' will
# work properly (i.e., refer to `conftest.exe'), while it won't with
# `rm'.
for ac_file in conftest.exe conftest conftest.*; do
  test -f "$ac_file" || continue
  case $ac_file in
    _AC_COMPILER_EXEEXT_REJECT ) ;;
    *.* ) ac_cv_exeext=`expr "$ac_file" : ['[^.]*\(\..*\)']`
	  break;;
    * ) break;;
  esac
done],
	      [AC_MSG_FAILURE([cannot compute suffix of executables: cannot compile and link])])
rm -f conftest$ac_cv_exeext
AC_MSG_RESULT([$ac_cv_exeext])
])# _AC_COMPILER_EXEEXT_O


# _AC_COMPILER_EXEEXT
# -------------------
# Check for the extension used for executables.  It compiles a test
# executable.  If this is called, the executable extensions will be
# automatically used by link commands run by the configure script.
#
# Note that some compilers (cross or not), strictly obey to `-o foo' while
# the host requires `foo.exe', so we should not depend upon `-o' to
# test EXEEXT.  But then, be sure not to destroy user files.
#
# Must be run before _AC_COMPILER_OBJEXT because _AC_COMPILER_EXEEXT_DEFAULT
# checks whether the compiler works.
m4_define([_AC_COMPILER_EXEEXT],
[AC_LANG_CONFTEST([AC_LANG_PROGRAM()])
ac_clean_files_save=$ac_clean_files
ac_clean_files="$ac_clean_files a.out a.exe b.out"
_AC_COMPILER_EXEEXT_DEFAULT
_AC_COMPILER_EXEEXT_WORKS
rm -f a.out a.exe conftest$ac_cv_exeext b.out
ac_clean_files=$ac_clean_files_save
_AC_COMPILER_EXEEXT_CROSS
_AC_COMPILER_EXEEXT_O
rm -f conftest.$ac_ext
AC_SUBST([EXEEXT], [$ac_cv_exeext])dnl
ac_exeext=$EXEEXT
])# _AC_COMPILER_EXEEXT


# _AC_COMPILER_OBJEXT
# -------------------
# Check the object extension used by the compiler: typically `.o' or
# `.obj'.  If this is called, some other behavior will change,
# determined by ac_objext.
#
# This macro is called by AC_LANG_COMPILER, the latter being required
# by the AC_COMPILE_IFELSE macros, so use _AC_COMPILE_IFELSE.  And in fact,
# don't, since _AC_COMPILE_IFELSE needs to know ac_objext for the `test -s'
# it includes.  So do it by hand.
m4_define([_AC_COMPILER_OBJEXT],
[AC_CACHE_CHECK([for suffix of object files], ac_cv_objext,
[AC_LANG_CONFTEST([AC_LANG_PROGRAM()])
rm -f conftest.o conftest.obj
AS_IF([_AC_DO_VAR(ac_compile)],
[for ac_file in conftest.o conftest.obj conftest.*; do
  test -f "$ac_file" || continue;
  case $ac_file in
    _AC_COMPILER_OBJEXT_REJECT ) ;;
    *) ac_cv_objext=`expr "$ac_file" : '.*\.\(.*\)'`
       break;;
  esac
done],
      [_AC_MSG_LOG_CONFTEST
AC_MSG_FAILURE([cannot compute suffix of object files: cannot compile])])
rm -f conftest.$ac_cv_objext conftest.$ac_ext])
AC_SUBST([OBJEXT], [$ac_cv_objext])dnl
ac_objext=$OBJEXT
])# _AC_COMPILER_OBJEXT





## ------------------------------- ##
## 4. Compilers' characteristics.  ##
## ------------------------------- ##

# AC_LANG_WERROR
# ------------------
# Treat warnings from the current language's preprocessor, compiler, and
# linker as fatal errors.
AC_DEFUN([AC_LANG_WERROR],
[m4_divert_text([DEFAULTS], [ac_[]_AC_LANG_ABBREV[]_werror_flag=no])
ac_[]_AC_LANG_ABBREV[]_werror_flag=yes])# AC_LANG_WERROR