ax_ext_check_header.m4

# Heavily modified, to try without any added includes first, and to set a
# HEADER_H_CPPFLAGS variable (for a file called header.h) instead of modifying
# CFLAGS/CPPFLAGS directly.

# ===========================================================================
#    http://www.gnu.org/software/autoconf-archive/ax_ext_check_header.html
# ===========================================================================
#
# SYNOPSIS
#
#   AX_EXT_CHECK_HEADER(<header>, <paths>).
#
# DESCRIPTION
#
#   Check for <header> with -I<path> for each path in <paths> if need be.
#   The first sucecssful path is chosen (eg if you say
#   AX_EXT_CHECK_HEADER(foo.h, bar baz qux) and -Ibaz works then -Iqux will
#   not be tested.
#
#   Any -I flags that locate a header are added to CFLAGS and CPPFLAGS. AS
#   with AC_CHECK_HEADERS it causes HAVE_<header>_H to be defined as 1.
#
#   Example:
#
#    AX_EXT_HAVE_HEADER(openssl/rsa.h, /usr/local/include /usr/local/ssl/include /usr/local/openssl/include)
#
# LICENSE
#
#   Copyright (c) 2008 Duncan Simpson <dps@simpson.demon.co.uk>
#
#   Copying and distribution of this file, with or without modification, are
#   permitted in any medium without royalty provided the copyright notice
#   and this notice are preserved. This file is offered as-is, without any
#   warranty.

#serial 7

AC_DEFUN([AX_EXT_HAVE_HEADER],
[AC_LANG_PUSH(C)
	got="no"
	hdr=`echo $1 | $as_tr_sh`
	AC_CACHE_CHECK([for $1], [ext_cv_hashdr_${hdr}],
	               AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <$1>])], [got="yes"], [got="no"]))
	if test "x$got" = "xyes"; then
		hdr=`echo $1 | $as_tr_cpp`
		eval ${hdr}_CPPFLAGS=""
	fi
	for dir in $2; do
		if test "x${got}" = "xno"; then
			ext_hashdr_cvdir=`echo $dir | $as_tr_sh`
			AC_CACHE_CHECK([for $1 with -I$dir], [ext_cv${ext_hashdr_cvdir}_hashdr_${hdr}],
			               [ext_have_hdr_save_cflags=${CFLAGS} CFLAGS="${CFLAGS} -I${dir}"
			               AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <$1>])],
			                                 [got="yes"; eval "ext_cv${ext_hashdr_cvdir}_hashdr_${hdr}"="yes"],
			                                 [got="no"; eval "ext_cv${ext_hashdr_cvdir}_hashdr_${hdr}"="no"])
			               CFLAGS=$ext_have_hdr_save_cflags])
			if eval `echo 'test x${'ext_cv${ext_hashdr_cvdir}_hashdr_${hdr}'}' = "xyes"`; then
				got="yes";
				hdr=`echo $1 | $as_tr_cpp`
				eval ${hdr}_CPPFLAGS=-I${dir}
			fi
		fi
	done
AC_LANG_POP])