Add support for version checks.

m4/ax_pkg_config.m4

@@ -28,7 +28,7 @@ dnl OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 dnl SUCH DAMAGE.
 dnl
 
-m4_define([AX_PKG_CONFIG_MACROS_VERSION], [0.20170404])
+m4_define([AX_PKG_CONFIG_MACROS_VERSION], [0.20180506])
 
 dnl
 dnl AX_PROG_PKG_CONFIG([min-version])
@@ -39,8 +39,10 @@ dnl
 AC_DEFUN([AX_PROG_PKG_CONFIG], [
     m4_pattern_forbid([^AX_PKG_CONFIG_[A-Z_]+$])
     AC_ARG_VAR([PKG_CONFIG], [path to pkg-config binary])
-    AC_ARG_VAR([PKG_CONFIG_PATH], [list of directories to prepend to default search path])
+    AC_ARG_VAR([PKG_CONFIG_PATH],
-    AC_ARG_VAR([PKG_CONFIG_LIBDIR], [list of directories to search instead of default search path])
+        [list of directories to prepend to default search path])
+    AC_ARG_VAR([PKG_CONFIG_LIBDIR],
+        [list of directories to search instead of default search path])
     if test x"${PKG_CONFIG}" = x"" ; then
         AC_PATH_PROGS([PKG_CONFIG], [pkgconf pkg-config]) >/dev/null
     else
@@ -97,12 +99,17 @@ AC_DEFUN([AX_PKG_CONFIG_VAR], [
 ])
 
 dnl
-dnl AX_PKG_CONFIG_CHECK(package-name,
+dnl AX_PKG_CONFIG_CHECK(package-name, [version-spec],
 dnl     [action-if-found], [action-if-not-found])
 dnl -------------------------------------------
 dnl
 dnl Check if the specified package is installed.  If it is, define
 dnl HAVE_PACKAGE, PACKAGE_VERSION, PACKAGE_CFLAGS and PACKAGE_LIBS.
+dnl
+dnl The second argument, if non-empty, specifies a minimum (>=1.2.3 or
+dnl >1.2.3), maximum (<=1.2.3 or <1.2.3) or exact (==1.2.3 or =1.2.3
+dnl or 1.2.3) version to look for.
+dnl
 dnl The specified actions are performed in addition to the standard
 dnl actions.
 dnl
@@ -110,10 +117,35 @@ AC_DEFUN([AX_PKG_CONFIG_CHECK], [
     AC_REQUIRE([AX_PROG_PKG_CONFIG])
     m4_define([_P], AS_TR_SH([m4_toupper([$1])]))
     m4_define([_p], AS_TR_SH([m4_tolower([$1])]))
+dnl
+    ver="$2"
+    ver="${ver##*\[<=>\]}"
+    case "$2" in
+    "")
+        vopt=""
+	vtext="$1"
+	;;
+    ">=$ver"|">$ver")
+	vopt="--atleast-version=$ver"
+	vtext="$1 $ver or newer"
+	;;
+    "<=$ver"|"<$ver")
+        vopt="--max-version=$ver"
+	vtext="$1 $ver or older"
+	;;
+    "==$ver"|"=$ver"|"$ver")
+        vopt="--exact-version=$ver"
+	vtext="$1 $ver"
+	;;
+    *)
+        AC_MSG_ERROR([invalid version specification: "$2"])
+	;;
+    esac
+dnl
     AC_ARG_VAR(_P[_CFLAGS], [C compiler flags for $1])
     AC_ARG_VAR(_P[_LIBS], [linker flags for $1])
-    AC_MSG_CHECKING([if $1 is installed])
+    AC_MSG_CHECKING([if ${vtext} is installed])
-    if AC_RUN_LOG(["${PKG_CONFIG}" --exists --print-errors "$1"]) ; then
+    if AC_RUN_LOG(["${PKG_CONFIG}" --exists $vopt --print-errors "$1"]) ; then
         AC_MSG_RESULT([yes])
         [ax_pc_cv_have_]_p=yes
         AC_DEFINE([HAVE_]_P, [1], [Define to 1 if you have $1])
@@ -133,11 +165,11 @@ dnl
         AC_SUBST(_P[_LIBS], [$ax_pc_cv_]_p[_libs])
         AC_MSG_RESULT([${ax_pc_cv_]_p[_libs:-none}])
 dnl
-        m4_default([$2], [:])
+        m4_default([$3], [:])
     else
         AC_MSG_RESULT([no])
         [ax_pc_cv_have_]_p=no
-        m4_default([$3], [:])
+        m4_default([$4], [:])
     fi
     m4_ifdef([AM_CONDITIONAL], [
         AM_CONDITIONAL([HAVE_]_P, [test x"$ax_pc_cv_have_]_p[" = x"yes"])
@@ -145,13 +177,13 @@ dnl
 ])
 
 dnl
-dnl AX_PKG_CONFIG_REQUIRE(package-name)
+dnl AX_PKG_CONFIG_REQUIRE(package-name, [version-spec])
 dnl -----------------------------------
 dnl
 dnl As above, but fail if the package is not installed.
 dnl
 AC_DEFUN([AX_PKG_CONFIG_REQUIRE], [
-    AX_PKG_CONFIG_CHECK([$1], [], [
+    AX_PKG_CONFIG_CHECK([$1], [$2], [], [
         AC_MSG_ERROR([cannot proceed without $1])
     ])
 ])