Introduce new macros for out-of-tree VMODs

With a bit of documentation to explain how to use the two new macros.

Closes #2054

Makefile.am

@@ -6,7 +6,7 @@ pkgconfigdir = $(libdir)/pkgconfig
 pkgconfig_DATA = varnishapi.pc
 
 m4dir = $(datadir)/aclocal
-m4_DATA = varnish-legacy.m4
+m4_DATA = varnish.m4 varnish-legacy.m4
 
 CLEANFILES = cscope.in.out cscope.out cscope.po.out
 EXTRA_DIST = \
@@ -15,6 +15,7 @@ EXTRA_DIST = \
 	LICENSE \
 	autogen.sh \
 	varnishapi.pc.in \
+	varnish.m4 \
 	varnish-legacy.m4
 
 DISTCHECK_CONFIGURE_FLAGS = \

varnish.m4

+# varnish.m4 - Macros to define VMOD builds.            -*- Autoconf -*-
+# serial 5 (varnish-4.1.4)
+
+# Copyright (c) 2016 Varnish Software AS
+# All rights reserved.
+#
+# Author: Dridi Boukelmoune <dridi.boukelmoune@gmail.com>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above
+#    copyright notice, this list of conditions and the following
+#    disclaimer.
+# 2. Redistributions in binary form must reproduce the above
+#    copyright notice, this list of conditions and the following
+#    disclaimer in the documentation and/or other materials
+#    provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+# STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+# OF THE POSSIBILITY OF SUCH DAMAGE.
+
+# _VARNISH_PKG_CONFIG
+# --------------------
+AC_DEFUN([_VARNISH_PKG_CONFIG], [
+	PKG_PROG_PKG_CONFIG([0.21])
+
+	PKG_CHECK_MODULES([VARNISHAPI], [varnishapi])
+	AC_SUBST([VARNISH_VERSION], [$($PKG_CONFIG --modversion varnishapi)])
+
+	PKG_CHECK_VAR([VARNISHAPI_PREFIX], [varnishapi], [prefix])
+	PKG_CHECK_VAR([VARNISHAPI_DATAROOTDIR], [varnishapi], [datarootdir])
+	PKG_CHECK_VAR([VARNISHAPI_BINDIR], [varnishapi], [bindir])
+	PKG_CHECK_VAR([VARNISHAPI_SBINDIR], [varnishapi], [sbindir])
+	PKG_CHECK_VAR([VARNISHAPI_VMODDIR], [varnishapi], [vmoddir])
+
+	PKG_CHECK_VAR([VMODTOOL], [varnishapi], [vmodtool])
+])
+
+# _VARNISH_CHECK_DEVEL
+# --------------------
+AC_DEFUN([_VARNISH_CHECK_DEVEL], [
+
+	AC_REQUIRE([_VARNISH_PKG_CONFIG])
+
+	[_orig_cppflags=$CPPFLAGS]
+	[CPPFLAGS=$VARNISHAPI_CFLAGS]
+
+	AC_CHECK_HEADERS([vsha256.h cache/cache.h], [],
+		[AC_MSG_ERROR([Missing Varnish development files.])])
+
+	[CPPFLAGS=$_orig_cppflags]
+])
+
+# _VARNISH_VMOD_CONFIG
+# --------------------
+AC_DEFUN([_VARNISH_VMOD_CONFIG], [
+
+	AC_REQUIRE([_VARNISH_PKG_CONFIG])
+	AC_REQUIRE([_VARNISH_CHECK_DEVEL])
+
+	dnl Check the VMOD toolchain
+	AC_REQUIRE([AC_LANG_C])
+	AC_REQUIRE([AC_PROG_CC_C99])
+	AC_REQUIRE([AC_PROG_CPP])
+	AC_REQUIRE([AC_PROG_CPP_WERROR])
+
+	AM_PATH_PYTHON([2.6], [], [
+		AC_MSG_ERROR([Python is needed to build VMODs.])
+	])
+
+	AS_IF([test -z "$RST2MAN"], [
+		AC_MSG_ERROR([rst2man is needed to build VMOD manuals.])
+	])
+
+	dnl Expose the location of the std and directors VMODs
+	AC_SUBST([VARNISHAPI_VMODDIR])
+
+	dnl Expose Varnish's aclocal directory to automake
+	AC_SUBST([VARNISHAPI_DATAROOTDIR])
+
+	dnl Define the VMOD directory for libtool
+	AS_CASE([$prefix],
+		[NONE], [
+			vmoddir=$VARNISHAPI_VMODDIR
+			ac_default_prefix=$VARNISHAPI_PREFIX],
+		[vmoddir=$libdir/varnish/vmods]
+	)
+	AC_SUBST([vmoddir])
+
+	dnl Define an automake silent execution for vmodtool
+	[am__v_VMODTOOL_0='@echo "  VMODTOOL" $<;']
+	[am__v_VMODTOOL_1='']
+	[am__v_VMODTOOL_='$(am__v_VMODTOOL_$(AM_DEFAULT_VERBOSITY))']
+	[AM_V_VMODTOOL='$(am__v_VMODTOOL_$(V))']
+	AC_SUBST([am__v_VMODTOOL_0])
+	AC_SUBST([am__v_VMODTOOL_1])
+	AC_SUBST([am__v_VMODTOOL_])
+	AC_SUBST([AM_V_VMODTOOL])
+
+	dnl Define VMODs LDFLAGS
+	AC_SUBST([VMOD_LDFLAGS],
+		"-module -export-dynamic -avoid-version -shared")
+
+	dnl Define the PATH for the test suite
+	AC_SUBST([VMOD_TEST_PATH],
+		[$VARNISHAPI_SBINDIR:$VARNISHAPI_BINDIR:$PATH])
+])
+
+# _VARNISH_VMOD(NAME)
+# -------------------
+AC_DEFUN([_VARNISH_VMOD], [
+
+	AC_REQUIRE([_VARNISH_VMOD_CONFIG])
+
+	VMOD_FILE="\$(abs_builddir)/.libs/libvmod_$1.so"
+	AC_SUBST(m4_toupper(VMOD_$1_FILE), [$VMOD_FILE])
+
+	VMOD_IMPORT="$1 from \\\"$VMOD_FILE\\\""
+	AC_SUBST(m4_toupper(VMOD_$1), [$VMOD_IMPORT])
+
+	VMOD_RULES="
+
+vmod_$1.lo: vcc_$1_if.c vcc_$1_if.h
+
+vcc_$1_if.h vmod_$1.rst vmod_$1.man.rst: vcc_$1_if.c
+
+vcc_$1_if.c: vmod_$1.vcc
+	\$(AM_V_VMODTOOL) $PYTHON $VMODTOOL -o vcc_$1_if \$(srcdir)/vmod_$1.vcc
+
+vmod_$1.3: vmod_$1.man.rst
+	$RST2MAN vmod_$1.man.rst vmod_$1.3
+
+clean: clean-vmod-$1
+
+distclean: clean-vmod-$1
+
+clean-vmod-$1:
+	rm -f vcc_$1_if.c vcc_$1_if.h
+	rm -f vmod_$1.rst vmod_$1.man.rst vmod_$1.3
+
+"
+
+	AC_SUBST(m4_toupper(BUILD_VMOD_$1), [$VMOD_RULES])
+	m4_ifdef([_AM_SUBST_NOTMAKE],
+		[_AM_SUBST_NOTMAKE(m4_toupper(BUILD_VMOD_$1))])
+])
+
+# VARNISH_VMODS(NAMES)
+# --------------------
+# Since: Varnish 4.1.4
+#
+# Set up the VMOD tool-chain to build the collection of NAMES modules. The
+# definition of key variables is made available for use in Makefile rules
+# to build the modules:
+#
+# - VMOD_LDFLAGS (the recommended flags to link VMODs)
+# - VMOD_TEST_PATH (for the test suite's environment)
+# - VMODTOOL (to generate a VMOD's interface)
+# - vmoddir (the install prefix for VMODs)
+#
+# Configuring your VMOD build with libtool can be as simple as:
+#
+#     AM_CFLAGS = $(VARNISHAPI_CFLAGS)
+#     AM_LDFLAGS = $(VARNISHAPI_LIBS) $(VMOD_LDFLAGS)
+#
+#     vmod_LTLIBRARIES = libvmod_foo.la
+#
+#     [...]
+#
+# Turnkey build rules are generated for each module, they are provided as
+# a convenience mechanism but offer no means of customizations. They make
+# use of the VMODTOOL variable automatically.
+#
+# For example, if you define the following in configure.ac:
+#
+#     VARNISH_VMODS([foo bar])
+#
+# Two build rules will be available for use in Makefile.am for vmod-foo
+# and vmod-bar:
+#
+#     vmod_LTLIBRARIES = libvmod_foo.la libvmod_bar.la
+#
+#     [...]
+#
+#     @BUILD_VMOD_FOO@
+#     @BUILD_VMOD_BAR@
+#
+# These two set of make rules are independent and may be used in separate
+# sub-directories. You still need to declare the generated VCC interfaces
+# in your library's sources. The generated files can be declared this way:
+#
+#     nodist_libvmod_foo_la_SOURCES = \
+#         vcc_foo_if.c \
+#         vcc_foo_if.h
+#
+#     nodist_libvmod_bar_la_SOURCES = \
+#         vcc_bar_if.c \
+#         vcc_bar_if.h
+#
+# The generated rules also build the manual page, all you need to do is to
+# declare the generated pages:
+#
+#     nodist_man_MANS = vmod_foo.3 vmod_bar.3
+#
+# However, it requires RST2MAN to be defined beforehand in configure.ac
+# and it is for now the VMOD's maintainer job to manage it. On the other
+# hand python detection is done and the resulting PYTHON variable to use
+# the VMODTOOL. Since nothing requires RST2MAN to be written in python, it
+# is left outside of the scope. You may even define a phony RST2MAN to
+# skip man page generation as it is often the case from a dist archive.
+#
+# Two notable variables are exposed from Varnish's pkg-config:
+#
+# - VARNISHAPI_VMODDIR (locate vmod-std and vmod-directors in your tests)
+# - VARNISHAPI_DATAROOTDIR (for when aclocal is called from a Makefile)
+#
+# For example in your root Makefile.am:
+#
+#     ACLOCAL_AMFLAGS = -I m4 -I ${VARNISHAPI_DATAROOTDIR}/aclocal
+#
+# The VARNISH_VERSION variable will be set even if the VARNISH_PREREQ isn't
+# called. Although many things are set up to facilitate VMOD maintenance,
+# initialization of autoconf, automake and libtool is still the maintainer's
+# responsibility.
+#
+AC_DEFUN([VARNISH_VMODS], [
+	m4_foreach([_vmod_name],
+		m4_split(m4_normalize([$1])),
+		[_VARNISH_VMOD(_vmod_name)])
+])
+
+# VARNISH_PREREQ(MINIMUM-VERSION, [MAXIMUM-VERSION])
+# --------------------------------------------------
+# Since: Varnish 4.1.4
+#
+# Verify that the version of Varnish Cache found by pkg-config is at least
+# MINIMUM-VERSION. If MAXIMUM-VERSION is specified, verify that the version
+# is strictly below MAXIMUM-VERSION.
+#
+# If the prerequisite is met, the variable VARNISH_VERSION is available.
+#
+AC_DEFUN([VARNISH_PREREQ], [
+	AC_REQUIRE([_VARNISH_PKG_CONFIG])
+	AC_MSG_CHECKING([for Varnish])
+	AC_MSG_RESULT([$VARNISH_VERSION])
+
+	AS_VERSION_COMPARE([$VARNISH_VERSION], [$1], [
+		AC_MSG_ERROR([Varnish version $1 or higher is required.])
+	])
+
+	test $# -gt 1 &&
+	AS_VERSION_COMPARE([$2], [$VARNISH_VERSION], [
+		AC_MSG_ERROR([Varnish version below $2 is required.])
+	])
+])