lang.m4

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# Written by David MacKenzie, with help from
# Franc,ois Pinard, Karl Berry, Richard Pixley, Ian Lance Taylor,
# Roland McGrath, Noah Friedman, david d zuhn, and many others.


# Table of Contents:
#
# 1. Language selection
#    and routines to produce programs in a given language.
#  a. generic routines
#  b. C
#  c. C++
#  d. Fortran 77
#
# 2. Producing programs in a given language.
#  a. generic routines
#  b. C
#  c. C++
#  d. Fortran 77
#
# 3. Looking for a compiler
#    And possibly the associated preprocessor.
#  a. Generic routines.
#  b. C
#  c. C++
#  d. Fortran 77
#
# 4. Compilers' characteristics.
#  a. Generic routines.
#  b. C
#  c. C++
#  d. Fortran 77



## ----------------------- ##
## 1. Language selection.  ##
## ----------------------- ##



# -------------------------------- #
# 1a. Generic language selection.  #
# -------------------------------- #

# AC_LANG_CASE(LANG1, IF-LANG1, LANG2, IF-LANG2, ..., DEFAULT)
# ------------------------------------------------------------
# Expand into IF-LANG1 if the current language is LANG1 etc. else
# into default.
m4_define([AC_LANG_CASE],
[m4_case(_AC_LANG, $@)])


# _AC_LANG_DISPATCH(MACRO, LANG, ARGS)
# ------------------------------------
# Call the specialization of MACRO for LANG with ARGS.  Complain if
# unavailable.
m4_define([_AC_LANG_DISPATCH],
[m4_ifdef([$1($2)],
       [m4_indir([$1($2)], m4_shiftn(2, $@))],
       [AC_FATAL([$1: unknown language: $2])])])


# _AC_LANG_SET(OLD, NEW)
# ----------------------
# Output the shell code needed to switch from OLD language to NEW language.
# Do not try to optimize like this:
#
# m4_defun([_AC_LANG_SET],
# [m4_if([$1], [$2], [],
#        [_AC_LANG_DISPATCH([AC_LANG], [$2])])])
#
# as it can introduce differences between the sh-current language and the
# m4-current-language when m4_require is used.  Something more subtle
# might be possible, but at least for the time being, play it safe.
m4_defun([_AC_LANG_SET],
[_AC_LANG_DISPATCH([AC_LANG], [$2])])


# AC_LANG(LANG)
# -------------
# Set the current language to LANG.
m4_defun([AC_LANG],
[_AC_LANG_SET(m4_ifdef([_AC_LANG], [m4_defn([_AC_LANG])]),
	      [$1])dnl
m4_define([_AC_LANG], [$1])])


# AC_LANG_PUSH(LANG)
# ------------------
# Save the current language, and use LANG.
m4_defun([AC_LANG_PUSH],
[_AC_LANG_SET(m4_ifdef([_AC_LANG], [m4_defn([_AC_LANG])]),
	      [$1])dnl
m4_pushdef([_AC_LANG], [$1])])


# AC_LANG_POP([LANG])
# -------------------
# If given, check that the current language is LANG, and restore the
# previous language.
m4_defun([AC_LANG_POP],
[m4_ifval([$1],
 [m4_if([$1], m4_defn([_AC_LANG]), [],
  [m4_fatal([$0($1): unexpected current language: ]m4_defn([_AC_LANG]))])])dnl
m4_pushdef([$0 OLD], m4_defn([_AC_LANG]))dnl
m4_popdef([_AC_LANG])dnl
_AC_LANG_SET(m4_defn([$0 OLD]), m4_defn([_AC_LANG]))dnl
m4_popdef([$0 OLD])dnl
])


# AC_LANG_SAVE
# ------------
# Save the current language, but don't change language.
AU_DEFUN([AC_LANG_SAVE],
[[AC_LANG_SAVE]],
[Instead of using `AC_LANG', `AC_LANG_SAVE', and `AC_LANG_RESTORE',
you should use `AC_LANG_PUSH' and `AC_LANG_POP'.])
AC_DEFUN([AC_LANG_SAVE],
[m4_pushdef([_AC_LANG], _AC_LANG)dnl
AC_DIAGNOSE([obsolete], [The macro `AC_LANG_SAVE' is obsolete.
You should run autoupdate.])])


# AC_LANG_RESTORE
# ---------------
# Restore the current language from the stack.
AU_DEFUN([AC_LANG_RESTORE], [AC_LANG_POP($@)])


# _AC_LANG_ABBREV
# ---------------
# Return a short signature of _AC_LANG which can be used in shell
# variable names, or in M4 macro names.
m4_defun([_AC_LANG_ABBREV],
[_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])


# _AC_LANG_PREFIX
# ---------------
# Return a short (upper case) signature of _AC_LANG that is used to
# prefix environment variables like FLAGS.
m4_defun([_AC_LANG_PREFIX],
[_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])


# AC_LANG_ASSERT(LANG)
# --------------------
# Current language must be LANG.
m4_defun([AC_LANG_ASSERT],
[m4_if(_AC_LANG, $1, [],
       [m4_fatal([$0: current language is not $1: ] _AC_LANG)])])



## ---------------------- ##
## 2.Producing programs.  ##
## ---------------------- ##


# ---------------------- #
# 2a. Generic routines.  #
# ---------------------- #


# AC_LANG_CONFTEST(BODY)
# ----------------------
# Save the BODY in `conftest.$ac_ext'.  Add a trailing new line.
AC_DEFUN([AC_LANG_CONFTEST],
[cat >conftest.$ac_ext <<_ACEOF
$1
_ACEOF])


# AC_LANG_SOURCE(BODY)
# --------------------
# Produce a valid source for the current language, which includes the
# BODY, and as much as possible `confdefs.h'.
AC_DEFUN([AC_LANG_SOURCE],
[_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])


# AC_LANG_PROGRAM([PROLOGUE], [BODY])
# -----------------------------------
# Produce a valid source for the current language.  Prepend the
# PROLOGUE (typically CPP directives and/or declarations) to an
# execution the BODY (typically glued inside the `main' function, or
# equivalent).
AC_DEFUN([AC_LANG_PROGRAM],
[AC_LANG_SOURCE([_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])])


# AC_LANG_CALL(PROLOGUE, FUNCTION)
# --------------------------------
# Call the FUNCTION.
AC_DEFUN([AC_LANG_CALL],
[m4_ifval([$2], [], [m4_warn([syntax], [$0: no function given])])dnl
_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])


# AC_LANG_FUNC_LINK_TRY(FUNCTION)
# -------------------------------
# Produce a source which links correctly iff the FUNCTION exists.
AC_DEFUN([AC_LANG_FUNC_LINK_TRY],
[m4_ifval([$1], [], [m4_warn([syntax], [$0: no function given])])dnl
_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])


# AC_LANG_BOOL_COMPILE_TRY(PROLOGUE, EXPRESSION)
# ----------------------------------------------
# Produce a program that compiles with success iff the boolean EXPRESSION
# evaluates to true at compile time.
AC_DEFUN([AC_LANG_BOOL_COMPILE_TRY],
[_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])


# AC_LANG_INT_SAVE(PROLOGUE, EXPRESSION)
# --------------------------------------
# Produce a program that saves the runtime evaluation of the integer
# EXPRESSION into `conftest.val'.
AC_DEFUN([AC_LANG_INT_SAVE],
[_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])


## -------------------------------------------- ##
## 3. Looking for Compilers and Preprocessors.  ##
## -------------------------------------------- ##

# ----------------------------------------------------- #
# 3a. Generic routines in compilers and preprocessors.  #
# ----------------------------------------------------- #

# AC_LANG_COMPILER
# ----------------
# Find a compiler for the current LANG.  Be sure to be run before
# AC_LANG_PREPROC.
#
# Note that because we might AC_REQUIRE `AC_LANG_COMPILER(C)' for
# instance, the latter must be AC_DEFUN'd, not just define'd.
m4_define([AC_LANG_COMPILER],
[AC_BEFORE([AC_LANG_COMPILER(]_AC_LANG[)],
	   [AC_LANG_PREPROC(]_AC_LANG[)])dnl
_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])


# AC_LANG_COMPILER_REQUIRE
# ------------------------
# Ensure we have a compiler for the current LANG.
AC_DEFUN([AC_LANG_COMPILER_REQUIRE],
[m4_require([AC_LANG_COMPILER(]_AC_LANG[)],
	    [AC_LANG_COMPILER])])



# _AC_LANG_COMPILER_GNU
# ---------------------
# Check whether the compiler for the current language is GNU.
#
# It doesn't seem necessary right now to have a different source
# according to the current language, since this works fine.  Some day
# it might be needed.  Nevertheless, pay attention to the fact that
# the position of `choke me' on the seventh column is meant: otherwise
# some Fortran compilers (e.g., SGI) might consider it's a
# continuation line, and warn instead of reporting an error.
m4_define([_AC_LANG_COMPILER_GNU],
[AC_CACHE_CHECK([whether we are using the GNU _AC_LANG compiler],
		[ac_cv_[]_AC_LANG_ABBREV[]_compiler_gnu],
[_AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [[#ifndef __GNUC__
       choke me
#endif
]])],
		   [ac_compiler_gnu=yes],
		   [ac_compiler_gnu=no])
ac_cv_[]_AC_LANG_ABBREV[]_compiler_gnu=$ac_compiler_gnu
])])# _AC_LANG_COMPILER_GNU


# AC_LANG_PREPROC
# ---------------
# Find a preprocessor for the current language.  Note that because we
# might AC_REQUIRE `AC_LANG_PREPROC(C)' for instance, the latter must
# be AC_DEFUN'd, not just define'd.  Since the preprocessor depends
# upon the compiler, look for the compiler.
m4_define([AC_LANG_PREPROC],
[AC_LANG_COMPILER_REQUIRE()dnl
_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])