Dedicated autoconf macros for libraries detection

They live as private macros in varnish.m4, which is now included in the
Varnish build during the autogen phase. This way it is now possible to
dogfood on macros we distribute downstream. Considering how simple they
are, they could be made public macros for the convenience of VMOD or VUT
writers.

We don't need to have the LIBS-saving-dance in configure.ac for every
single dependency.

autogen.sh

@@ -45,7 +45,7 @@ fi
 set -ex
 
 $LIBTOOLIZE --copy --force
-aclocal -I m4
+aclocal -I m4 -I .
 autoheader
 automake --add-missing --copy --foreign
 autoconf

bin/varnishd/Makefile.am

@@ -157,7 +157,7 @@ varnishd_LDADD = \
 	@SAN_LDFLAGS@ \
 	@JEMALLOC_LDADD@ \
 	@PCRE_LIBS@ \
-	${DL_LIBS} ${PTHREAD_LIBS} ${NET_LIBS} ${LIBM} ${LIBUMEM}
+	${DL_LIBS} ${PTHREAD_LIBS} ${NET_LIBS} ${LIBM} ${UMEM_LIBS}
 
 noinst_PROGRAMS = vhp_gen_hufdec
 vhp_gen_hufdec_SOURCES = hpack/vhp_gen_hufdec.c

configure.ac

@@ -65,40 +65,18 @@ AC_ARG_WITH([dot],
 AM_CONDITIONAL(HAVE_DOT,[test "x$DOT" != "xno"])
 
 # Checks for libraries.
-save_LIBS="${LIBS}"
-LIBS=""
-AC_CHECK_LIB(rt, clock_gettime)
-RT_LIBS="${LIBS}"
-LIBS="${save_LIBS}"
-AC_SUBST(RT_LIBS)
-
-save_LIBS="${LIBS}"
-LIBS=""
-AC_CHECK_LIB(dl, dlopen)
-DL_LIBS="${LIBS}"
-LIBS="${save_LIBS}"
-AC_SUBST(DL_LIBS)
+_VARNISH_SEARCH_LIBS(pthread, pthread_create, [thr pthread c_r])
+_VARNISH_CHECK_LIB(rt, clock_gettime)
+_VARNISH_CHECK_LIB(dl, dlopen)
+_VARNISH_CHECK_LIB(socket, socket)
+_VARNISH_CHECK_LIB(nsl, getaddrinfo)
+NET_LIBS="${SOCKET_LIBS} ${NSL_LIBS}"
 
 AX_WITH_CURSES
 if test "x$ax_cv_curses" != xyes; then
    AC_MSG_ERROR([requires an X/Open-compatible Curses library])
 fi
 
-save_LIBS="${LIBS}"
-LIBS=""
-AC_SEARCH_LIBS(pthread_create, [thr pthread c_r])
-PTHREAD_LIBS="${LIBS}"
-LIBS="${save_LIBS}"
-AC_SUBST(PTHREAD_LIBS)
-
-save_LIBS="${LIBS}"
-LIBS=""
-AC_CHECK_LIB(socket, socket)
-AC_CHECK_LIB(nsl, getaddrinfo)
-NET_LIBS="${LIBS}"
-LIBS="${save_LIBS}"
-AC_SUBST(NET_LIBS)
-
 # XXX: This _may_ be for OS/X
 AC_CHECK_LIBM
 AC_SUBST(LIBM)
@@ -320,17 +298,9 @@ AC_SUBST(JEMALLOC_LDADD)
 # Userland slab allocator, available only on Solaris
 case $target in
 *-*-solaris*)
-	AC_CHECK_HEADERS([umem.h])
-	if test "$ac_cv_have_umem_h" = yes; then
-		save_LIBS="${LIBS}"
-		LIBS=""
-		AC_CHECK_LIB(umem, umem_alloc)
-		LIBUMEM="${LIBS}"
-		LIBS="${save_LIBS}"
-	fi
+	AC_CHECK_HEADERS([umem.h], [_VARNISH_CHECK_LIB(umem, umem_alloc)])
 	;;
 esac
-AC_SUBST(LIBUMEM)
 
 # These functions are provided by libcompat on platforms where they
 # are not available

varnish.m4

@@ -42,6 +42,26 @@
 # any time. Public macros starting with VARNISH_ are documented and will
 # maintain backwards compatibility with older versions of Varnish Cache.
 
+# _VARNISH_CHECK_LIB(LIB, FUNC)
+# -----------------------------
+AC_DEFUN([_VARNISH_CHECK_LIB], [
+	save_LIBS="${LIBS}"
+	LIBS=""
+	AC_CHECK_LIB([$1], [$2])
+	AC_SUBST(m4_toupper($1_LIBS), [$LIBS])
+	LIBS="${save_LIBS}"
+])
+
+# _VARNISH_SEARCH_LIBS(VAR, FUNC, LIBS)
+# -------------------------------------
+AC_DEFUN([_VARNISH_SEARCH_LIBS], [
+	save_LIBS="${LIBS}"
+	LIBS=""
+	AC_SEARCH_LIBS([$2], [$3])
+	AC_SUBST(m4_toupper($1_LIBS), [$LIBS])
+	LIBS="${save_LIBS}"
+])
+
 # _VARNISH_PKG_CONFIG
 # --------------------
 AC_DEFUN([_VARNISH_PKG_CONFIG], [