Support older pkg-config packages

Resolve the pkg-config 0.28 or greater dependency introduced by
the patch "Add bash completion to the install routine."

1 files changed, 17 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index 1de0808..bb6d673 100644
--- a/configure.ac
+++ b/configure.ac
@@ -45,6 +45,23 @@ AC_ARG_ENABLE([bashcompl],
 	[Install bash completion for ipset]),
 	[enable_bashcompl="$enableval"], [enable_bashcompl="no"])
 
+# backward compatibility with older pkg-config
+m4_ifndef([PKG_CHECK_VAR], [
+# PKG_CHECK_VAR(VARIABLE, MODULE, CONFIG-VARIABLE,
+# [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
+# -------------------------------------------
+# Retrieves the value of the pkg-config variable for the given module.
+AC_DEFUN([PKG_CHECK_VAR],
+[AC_REQUIRE([PKG_PROG_PKG_CONFIG])dnl
+AC_ARG_VAR([$1], [value of $3 for $2, overriding pkg-config])dnl
+
+_PKG_CONFIG([$1], [variable="][$3]["], [$2])
+AS_VAR_COPY([$1], [pkg_cv_][$1])
+
+AS_VAR_IF([$1], [""], [$5], [$4])dnl
+])# PKG_CHECK_VAR
+])
+
 if test "x$enable_bashcompl" = "xyes"; then
 	PKG_CHECK_VAR(bashcompdir, [bash-completion], [completionsdir], , bashcompdir="${sysconfdir}/bash_completion.d")
 	AC_SUBST(bashcompdir)