Build: Move custom Autoconf macros to separate file

Place custom Autoconf macros which other sigrok modules may
re-use into a separate file m4/sigrok.m4. Also, introduce new
macros for defining the package and library versions, and for
gathering compiler warning flags.

configure.ac

@@ -21,17 +21,12 @@
 # We require at least autoconf 2.63 (AC_INIT format changed there).
 AC_PREREQ([2.63])
 
-# libsigrok package version number (NOT the same as shared lib version!).
+AC_INIT([libsigrok], [0.4.0],
-m4_define([sr_package_version_major], [0])
-m4_define([sr_package_version_minor], [4])
-m4_define([sr_package_version_micro], [0])
-
-AC_INIT([libsigrok], [sr_package_version_major.sr_package_version_minor.sr_package_version_micro],
 	[sigrok-devel@lists.sourceforge.net],
 	[libsigrok], [http://www.sigrok.org])
-AC_CONFIG_HEADERS([config.h include/libsigrok/version.h])
 AC_CONFIG_MACRO_DIR([m4])
 AC_CONFIG_AUX_DIR([autostuff])
+AC_CONFIG_HEADERS([config.h include/libsigrok/version.h])
 
 # We require at least automake 1.11 (needed for 'silent rules').
 AM_INIT_AUTOMAKE([1.11 -Wall -Werror no-define nostdinc subdir-objects check-news color-tests])
@@ -62,51 +57,14 @@ AM_PROG_CC_C_O
 # Initialize libtool.
 LT_INIT
 
-CONFIG_STATUS_DEPENDENCIES=
+# Set up the libsigrok version defines.
-SR_PACKAGE_VERSION="AC_PACKAGE_VERSION"
+SR_PKG_VERSION_SET([SR_PACKAGE_VERSION], [AC_PACKAGE_VERSION])
-
-# Check if we can get revision information from git.
-sr_head=`git -C "$srcdir" rev-parse --verify --short HEAD 2>&AS_MESSAGE_LOG_FD`
-
-AS_IF([test "$?" -eq 0 && test -n "$sr_head"], [
-	sr_git_deps=
-	test ! -f "$srcdir/.git/HEAD" || sr_git_deps=' $(top_srcdir)/.git/HEAD'
-
-	sr_head_name=`git -C "$srcdir" rev-parse --symbolic-full-name HEAD 2>&AS_MESSAGE_LOG_FD`
-	AS_IF([test "$?" -eq 0 && test -f "$srcdir/.git/$sr_head_name"],
-		[sr_git_deps="$sr_git_deps \$(top_srcdir)/.git/$sr_head_name"])
-
-	# Use $(wildcard) so that things do not break if for whatever
-	# reason these files do not exist anymore at make time.
-	test -z "$sr_git_deps" || CONFIG_STATUS_DEPENDENCIES="\$(wildcard$sr_git_deps)"
-
-	# Append the revision hash unless we are exactly on a tagged release.
-	git -C "$srcdir" describe --match 'AC_PACKAGE_NAME-AC_PACKAGE_VERSION' \
-		--exact-match >&AS_MESSAGE_LOG_FD 2>&AS_MESSAGE_LOG_FD \
-	|| SR_PACKAGE_VERSION="$SR_PACKAGE_VERSION-git-$sr_head"
-])
-AC_SUBST([CONFIG_STATUS_DEPENDENCIES])
-AC_SUBST([SR_PACKAGE_VERSION])
-
-AC_DEFINE([SR_PACKAGE_VERSION_MAJOR], [sr_package_version_major], [.])
-AC_DEFINE([SR_PACKAGE_VERSION_MINOR], [sr_package_version_minor], [.])
-AC_DEFINE([SR_PACKAGE_VERSION_MICRO], [sr_package_version_micro], [.])
-AC_DEFINE_UNQUOTED([SR_PACKAGE_VERSION_STRING], ["$SR_PACKAGE_VERSION"], [.])
 
 # Library version for libsigrok (NOT the same as the package version).
 # Carefully read the libtool docs before updating these numbers!
 # The algorithm for determining which number to change (and how) is nontrivial!
 # http://www.gnu.org/software/libtool/manual/libtool.html#Updating-version-info
-SR_LIB_VERSION_CURRENT=2
+SR_LIB_VERSION_SET([SR_LIB_VERSION], [2:0:0])
-SR_LIB_VERSION_REVISION=0
-SR_LIB_VERSION_AGE=0
-AC_SUBST([SR_LIB_VERSION],
-	["$SR_LIB_VERSION_CURRENT:$SR_LIB_VERSION_REVISION:$SR_LIB_VERSION_AGE"])
-
-AC_DEFINE_UNQUOTED([SR_LIB_VERSION_CURRENT], [$SR_LIB_VERSION_CURRENT], [.])
-AC_DEFINE_UNQUOTED([SR_LIB_VERSION_REVISION], [$SR_LIB_VERSION_REVISION], [.])
-AC_DEFINE_UNQUOTED([SR_LIB_VERSION_AGE], [$SR_LIB_VERSION_AGE], [.])
-AC_DEFINE_UNQUOTED([SR_LIB_VERSION_STRING], ["$SR_LIB_VERSION"], [.])
 
 #############################
 ##  Optional dependencies  ##

m4/sigrok.m4

@@ -0,0 +1,182 @@
+## Copyright (c) 2009  Openismus GmbH
+## Copyright (c) 2015  Daniel Elstner <daniel.kitta@gmail.com>
+##
+## This file is part of the sigrok project.
+##
+## sigrok is free software: you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## sigrok is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with sigrok. If not, see <http://www.gnu.org/licenses/>.
+
+#serial 20150821
+
+## SR_APPEND(var-name, [list-sep,] element)
+##
+## Append the shell word <element> to the shell variable named <var-name>,
+## prefixed by <list-sep> unless the list was empty before appending. If
+## only two arguments are supplied, <list-sep> defaults to a single space
+## character.
+##
+AC_DEFUN([SR_APPEND],
+[dnl
+m4_assert([$# >= 2])[]dnl
+$1=[$]{$1[}]m4_if([$#], [2], [[$]{$1:+' '}$2], [[$]{$1:+$2}$3])[]dnl
+])
+
+## _SR_PKG_VERSION_SET(var-prefix, pkg-name, tag-prefix, base-version, major, minor, [micro])
+##
+m4_define([_SR_PKG_VERSION_SET],
+[dnl
+m4_assert([$# >= 6])[]dnl
+$1=$4
+sr_git_deps=
+# Check if we can get revision information from git.
+sr_head=`git -C "$srcdir" rev-parse --verify --short HEAD 2>&AS_MESSAGE_LOG_FD`
+
+AS_IF([test "$?" = 0 && test "x$sr_head" != x], [dnl
+	test ! -f "$srcdir/.git/HEAD" \
+		|| sr_git_deps="$sr_git_deps \$(top_srcdir)/.git/HEAD"
+
+	sr_head_name=`git -C "$srcdir" rev-parse --symbolic-full-name HEAD 2>&AS_MESSAGE_LOG_FD`
+	AS_IF([test "$?" = 0 && test -f "$srcdir/.git/$sr_head_name"],
+		[sr_git_deps="$sr_git_deps \$(top_srcdir)/.git/$sr_head_name"])
+
+	# Append the revision hash unless we are exactly on a tagged release.
+	git -C "$srcdir" describe --match "$3$4" \
+		--exact-match >&AS_MESSAGE_LOG_FD 2>&AS_MESSAGE_LOG_FD \
+		|| $1="[$]$1-git-$sr_head"
+])
+# Use $(wildcard) so that things do not break if for whatever
+# reason these files do not exist anymore at make time.
+AS_IF([test -n "$sr_git_deps"],
+	[SR_APPEND([CONFIG_STATUS_DEPENDENCIES], ["\$(wildcard$sr_git_deps)"])])
+AC_SUBST([CONFIG_STATUS_DEPENDENCIES])[]dnl
+AC_SUBST([$1])[]dnl
+dnl
+AC_DEFINE([$1_MAJOR], [$5], [Major version number of $2.])[]dnl
+AC_DEFINE([$1_MINOR], [$6], [Minor version number of $2.])[]dnl
+m4_ifval([$7], [AC_DEFINE([$1_MICRO], [$7], [Micro version number of $2.])])[]dnl
+AC_DEFINE_UNQUOTED([$1_STRING], ["[$]$1"], [Version of $2.])[]dnl
+])
+
+## SR_PKG_VERSION_SET(var-prefix, version-triple)
+##
+## Set up substitution variables and macro definitions for the package
+## version components. Derive the version suffix from the repository
+## revision if possible.
+##
+## Substitutions: <var-prefix>
+## Macro defines: <var-prefix>_{MAJOR,MINOR,MICRO,STRING}
+##
+AC_DEFUN([SR_PKG_VERSION_SET],
+[dnl
+m4_assert([$# >= 2])[]dnl
+_SR_PKG_VERSION_SET([$1],
+	m4_defn([AC_PACKAGE_NAME]),
+	m4_defn([AC_PACKAGE_TARNAME])[-],
+	m4_expand([$2]),
+	m4_unquote(m4_split(m4_expand([$2]), [\.])))
+])
+
+## _SR_LIB_VERSION_SET(var-prefix, pkg-name, abi-triple, current, revision, age)
+##
+m4_define([_SR_LIB_VERSION_SET],
+[dnl
+m4_assert([$# >= 6])[]dnl
+$1=$3
+AC_SUBST([$1])[]dnl
+AC_DEFINE([$1_CURRENT], [$4], [Binary version of $2.])[]dnl
+AC_DEFINE([$1_REVISION], [$5], [Binary revision of $2.])[]dnl
+AC_DEFINE([$1_AGE], [$6], [Binary age of $2.])[]dnl
+AC_DEFINE([$1_STRING], ["$3"], [Binary version triple of $2.])[]dnl
+])
+
+## SR_LIB_VERSION_SET(var-prefix, abi-triple)
+##
+## Set up substitution variables and macro definitions for a library
+## binary version.
+##
+## Substitutions: <var-prefix>
+## Macro defines: <var-prefix>_{CURRENT,REVISION,AGE,STRING}
+##
+AC_DEFUN([SR_LIB_VERSION_SET],
+[dnl
+m4_assert([$# >= 1])[]dnl
+_SR_LIB_VERSION_SET([$1],
+	m4_defn([AC_PACKAGE_NAME]),
+	[$2], m4_unquote(m4_split([$2], [:])))
+])
+
+## _SR_ARG_ENABLE_WARNINGS_ONCE
+##
+## Implementation helper macro of SR_ARG_ENABLE_WARNINGS. Pulled in
+## through AC_REQUIRE so that it is only expanded once.
+##
+m4_define([_SR_ARG_ENABLE_WARNINGS_ONCE],
+[dnl
+AC_PROVIDE([$0])[]dnl
+AC_ARG_ENABLE([warnings],
+		[AS_HELP_STRING([[--enable-warnings[=min|max|fatal|no]]],
+				[set compile pedantry level [default=min]])],
+		[sr_enable_warnings=$enableval],
+		[sr_enable_warnings=min])[]dnl
+dnl
+# Test whether the compiler accepts each flag.  Look at standard output,
+# since GCC only shows a warning message if an option is not supported.
+sr_check_compile_warning_flags() {
+	for sr_flag
+	do
+		sr_cc_out=`$sr_cc $sr_warning_flags $sr_flag -c "$sr_conftest" 2>&1 || echo failed`
+		AS_IF([test "$?$sr_cc_out" = 0],
+			[SR_APPEND([sr_warning_flags], [$sr_flag])],
+			[AS_ECHO(["$sr_cc: $sr_cc_out"]) >&AS_MESSAGE_LOG_FD])
+		rm -f "conftest.[$]{OBJEXT:-o}"
+	done
+}
+])
+
+## SR_ARG_ENABLE_WARNINGS(variable, min-flags, max-flags)
+##
+## Provide the --enable-warnings configure argument, set to "min" by default.
+## <min-flags> and <max-flags> should be space-separated lists of compiler
+## warning flags to use with --enable-warnings=min or --enable-warnings=max,
+## respectively. Warning level "fatal" is the same as "max" but in addition
+## enables -Werror mode.
+##
+## In order to determine the warning options to use with the C++ compiler,
+## call AC_LANG([C++]) first to change the current language. If different
+## output variables are used, it is also fine to call SR_ARG_ENABLE_WARNINGS
+## repeatedly, once for each language setting.
+##
+AC_DEFUN([SR_ARG_ENABLE_WARNINGS],
+[dnl
+m4_assert([$# >= 3])[]dnl
+AC_REQUIRE([_SR_ARG_ENABLE_WARNINGS_ONCE])[]dnl
+dnl
+AS_CASE([$ac_compile],
+	[[*'$CXXFLAGS '*]], [sr_lang='C++' sr_cc=$CXX sr_conftest="conftest.[$]{ac_ext:-cc}"],
+	[[*'$CFLAGS '*]],   [sr_lang=C sr_cc=$CC sr_conftest="conftest.[$]{ac_ext:-c}"],
+	[AC_MSG_ERROR([[current language is neither C nor C++]])])
+dnl
+AC_MSG_CHECKING([which $sr_lang compiler warning flags to use])
+sr_warning_flags=
+AC_LANG_CONFTEST([AC_LANG_SOURCE([[
+int main(int argc, char** argv) { return (argv != 0) ? argc : 0; }
+]])])
+AS_CASE([$sr_enable_warnings],
+	[no], [],
+	[max], [sr_check_compile_warning_flags $3],
+	[fatal], [sr_check_compile_warning_flags $3 -Werror],
+	[sr_check_compile_warning_flags $2])
+rm -f "$sr_conftest"
+AC_SUBST([$1], [$sr_warning_flags])
+AC_MSG_RESULT([[$]{sr_warning_flags:-none}])[]dnl
+])