diff --git a/src/gpg-error-config.in b/src/gpg-error-config.in
index d5e2f3b..49451e7 100644
--- a/src/gpg-error-config.in
+++ b/src/gpg-error-config.in
@@ -1,392 +1,539 @@
 #!/bin/sh
 # Copyright (C) 1999, 2002, 2003 Free Software Foundation, Inc.
 #
 # This file is free software; as a special exception the author gives
 # unlimited permission to copy and/or distribute it, with or without
 # modifications, as long as this notice is preserved.
 #
 # This file is distributed in the hope that it will be useful, but
 # WITHOUT ANY WARRANTY, to the extent permitted by law; without even the
 # implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 # SPDX-License-Identifier: FSFULLR
 
 prefix=@prefix@
 datarootdir=@datarootdir@
 datadir=@datadir@
 PKG_CONFIG_PATH="$PKG_CONFIG_PATH${PKG_CONFIG_PATH:+:}${datadir}/pkgconfig"
 #
 
 #### start of pkgconf-funcs
 
 #
 # Bourne shell functions for config file in pkg-config style, so that
 # we can share such a config file between pkg-config and script
 #
 
 #
 # get_var: Get the variable value of NAME
 #
 # Variables are recorded in the shell variables named "VAR_<NAME>"
 #
 get_var () {
     local name=$1
 
     eval echo \$VAR_$name
 }
 
 #
 # get_attr: Get the attribute value of KEY
 #
 # Attributes are recorded in the shell variables named "ATTR_<KEY>"
 #
 get_attr () {
     local name=$1
 
     eval echo \$ATTR_$name
 }
 
 # Remove ${varname} part in the beginning of a string.
 remove_var_expr () {
     local varname=$1
     shift
 
     eval echo \"\${@#\\\$\\\{$varname\\\}}\"
 }
 
 # Given a string, substitute variables.
 substitute_vars () {
     local string="$1"
     local line
     local varname
     local result
 
     while [ -n "$string" ]; do
 	case "$string" in
 	    \$\$*)
 		result="$result\$"
 		string="${string#\$\$}"
 		;;
 	    \${*}*)
 		varname="${string#\$\{}"
 		varname="${varname%%\}*}"
 		result="$result$(get_var ${varname})"
 		string=$(remove_var_expr ${varname} ${string})
 		;;
 	    *)
 		result="${result}$(printf %c "$string")"
 		string="${string#$(printf %c "$string")}"
 		;;
 	esac
     done
 
     echo "$result"
 }
 
 #
 # Read a config from stdin
 #
 # Variables:
 # For VAR=VALUE, value is stored in the shell variable VAR_*.
 #
 # Attributes:
 # For KEY: VALUE, value is stored in the shell variable ATTR_*.
 #
 read_config_from_stdin () {
+    local filename=$1
     local line
     local varname
     local value
     local key
+    local reading_attrs
 
     while read line; do
-	case "$line" in
-	    *=*)
-		varname="${line%%=*}"
-		value="${line#*=}"
-		VAR_list="$VAR_list VAR_$varname"
-		read VAR_$varname <<EOF1
+	if [ -z "$line" ]; then
+	    reading_attrs=yes
+	    continue
+	elif [ -z "$reading_attrs" ]; then
+	    case "$line" in
+		*=*)
+		    varname="${line%%=*}"
+		    value="${line#*=}"
+		    VAR_list="$VAR_list VAR_$varname"
+		    read VAR_$varname <<EOF1
 $(substitute_vars "$value")
 EOF1
-		;;
-	    *:\ *)
-		key="${line%%:\ *}"
-		value="${line#*:\ }"
-		ATTR_list="$ATTR_list ATTR_$key"
-		read ATTR_$key <<EOF2
+		    continue
+		    ;;
+		*) reading_attrs=yes ;;
+	    esac
+	fi
+	if [ -n "$reading_attrs" ]; then
+	    case "$line" in
+		*:\ *)
+		    key="${line%%:\ *}"
+		    value="${line#*:\ }"
+		    ATTR_list="$ATTR_list ATTR_$key"
+		    read ATTR_$key <<EOF2
 $(substitute_vars "$value")
 EOF2
-		;;
-	esac
+		    ;;
+		*:|*:\ ) ;;
+		*)
+		    echo "Error reading $filename: $line" 1>&2
+		    exit 1
+		    ;;
+	    esac
+	fi
     done
 }
 
 
 find_file_in_path () {
     local f=$1
     local p=$2
     local IFS=":"		# On Windows it should be ";"???
 
     for d in $p; do
 	if [ -r $d/$f ]; then
 	    RESULT="$d/$f"
 	    return 0
 	fi
     done
     RESULT=""
     return 1
 }
 
 read_config_file () {
     local config_file
     local RESULT
 
     if find_file_in_path $1.pc $2; then
 	config_file=$RESULT
     else
 	echo "Can't find $1.pc" 1>&2
 	exit 1
     fi
-    read_config_from_stdin < $config_file
+    read_config_from_stdin $config_file < $config_file
 }
 
 cleanup_vars_attrs () {
     eval unset $VAR_list VAR_list
     eval unset $ATTR_list ATTR_list
 }
 
 not_listed_yet () {
     local m=$1
     local arg
     shift
 
     for arg; do
 	if [ $m = $arg ]; then
 	    return 1
 	fi
     done
 
     return 0
 }
 
 list_only_once () {
     local result=""
     local arg
 
     for arg; do
 	if not_listed_yet $arg $result; then
 	    result="$result $arg"
 	fi
     done
 
     echo $result
 }
 
 list_only_once_for_libs () {
     local result=""
     local rev_list=""
     local arg
 
     # Scan the list and eliminate duplicates for non-"-lxxx"
     # the resulted list is in reverse order
     for arg; do
 	case "$arg" in
 	    -l*)
 		# As-is
 		rev_list="$arg $rev_list"
 		;;
 	    *)
 		if not_listed_yet $arg $rev_list; then
 		    rev_list="$arg $rev_list"
 		fi
 		;;
 	esac
     done
 
     # Scan again
     for arg in $rev_list; do
 	case "$arg" in
 	    -l*)
 		if not_listed_yet $arg $result; then
 		    result="$arg $result"
 		fi
 		;;
 	    *)
 		# As-is
 		result="$arg $result"
 		;;
 	esac
     done
 
     echo $result
 }
 
+arg1_is_same () {
+    [ "$1" = "=" -o "$1" = ">=" -o "$1" = "<=" ]
+}
+
+arg1_is_less () {
+    [ "$1" = "!=" -o "$1" = "<" -o "$1" = "<=" ]
+}
+
+arg1_is_great () {
+    [ "$1" = "!=" -o "$1" = ">" -o "$1" = ">=" ]
+}
+
+#
+# Evaluate comparison between versions in RPM way
+#
+eval_compare_version () {
+    local str1="$1"
+    local cmp="$2"
+    local str2="$3"
+    local char1 char2
+    local chunk1 chunk2
+
+    while [ -n "$str1" -a -n "$str2" ]; do
+	# Trim anything that's not alnum or tilde from the front
+	str1="$(expr "$str1" : '[^0-9A-Za-z~]*\(.*\)')"
+	str2="$(expr "$str2" : '[^0-9A-Za-z~]*\(.*\)')"
+
+	# Get the first character
+	char1=${str1%${str1#?}}
+	char2=${str2%${str2#?}}
+
+	if [ "$char1" = ~ -o "$char2" = ~ ]; then
+	    if [ "$char1" != ~ ]; then
+		arg1_is_great $cmp
+		return
+	    fi
+	    if [ "$char2" != ~ ]; then
+		arg1_is_less $cmp
+		return
+	    fi
+	    str1=${str1#~}
+	    str2=${str2#~}
+	    continue
+	fi
+
+	if [ -z "$char1" -o -z "$char2" ]; then
+	    break
+	fi
+
+	case "$char1$char2" in
+	    [0-9][A-Za-z])
+		arg1_is_great $cmp
+		return
+		;;
+	    [A-Za-z][0-9])
+		arg1_is_less $cmp
+		return
+		;;
+	    [0-9][0-9])
+		chunk1="$(expr "$str1" : '\([0-9]*\)')"
+		chunk2="$(expr "$str2" : '\([0-9]*\)')"
+		;;
+	    [A-Za-z][A-Za-z])
+		chunk1="$(expr "$str1" : '\([A-Za-z]*\)')"
+		chunk2="$(expr "$str2" : '\([A-Za-z]*\)')"
+		;;
+	esac
+
+	# Compare chunks numerically if digits, or lexicographically
+	if expr "$chunk1" "!=" "$chunk2" >/dev/null; then
+	    if expr "$chunk1" ">" "$chunk2" >/dev/null; then
+		arg1_is_great $cmp
+		return
+	    else
+		arg1_is_less $cmp
+		return
+	    fi
+	fi
+
+	# Remove the chunk
+	str1="${str1#$chunk1}"
+	str2="${str2#$chunk2}"
+    done
+
+    # Either STR1, STR2 or both is empty here
+    if [ -n "$str1" ]; then
+	case "$str1" in
+	    ~*) arg1_is_less $cmp ;;
+	    *)  arg1_is_great $cmp ;;
+	esac
+    elif [ -n "$str2" ]; then
+	case "$str2" in
+	    ~*) arg1_is_great $cmp ;;
+	    *)  arg1_is_less $cmp ;;
+	esac
+    else
+	arg1_is_same $cmp
+    fi
+}
+
 #
 # Recursively solve package dependencies
 #
-# XXX: version requirement (version comparison) is not yet supported
+# Result is in the pkg_list variable
 #
 all_required_config_files () {
     local list
     local all_list
     local new_list
-    local p
-
-    list="$@"
-    all_list="$list"
+    local p pkg cmp ver
 
+    list=$*
     while [ -n "$list" ]; do
-	new_list=""
 	for p in $list; do
-	    read_config_file $p $PKG_CONFIG_PATH
+	    if [ -z "$pkg" ]; then
+		pkg=$p
+	    elif [ -z "$cmp" ]; then
+		case "$p" in
+		    "="|"!="|"<"|">"|"<="|">=") cmp=$p ;;
+		    *)
+			read_config_file $pkg $PKG_CONFIG_PATH
+			all_list="$all_list $pkg"
+			new_list="$new_list $(get_attr Requires)"
+			cleanup_vars_attrs
+			pkg=$p
+			;;
+		esac
+	    else
+		read_config_file $pkg $PKG_CONFIG_PATH
+		if ! eval_compare_version "$(get_attr Version)" $cmp $p; then
+		    echo "Version mismatch for $pkg $cmp $p: $(get_attr Version)" 1>&2
+		    exit 1
+		fi
+		all_list="$all_list $pkg"
+		new_list="$new_list $(get_attr Requires)"
+		cleanup_vars_attrs
+		pkg=
+		cmp=
+	    fi
+	done
+	if [ -n "$cmp" ]; then
+	    echo "No version after comparison operator ($cmp): $pkg" 1>&2
+	    exit 1
+	elif [ -n "$pkg" ]; then
+	    read_config_file $pkg $PKG_CONFIG_PATH
+	    all_list="$all_list $pkg"
 	    new_list="$new_list $(get_attr Requires)"
 	    cleanup_vars_attrs
-	done
-	all_list="$all_list $new_list"
+	fi
+
 	list="$new_list"
+	new_list=""
     done
 
-    echo $(list_only_once $all_list)
+    pkg_list=$(list_only_once $all_list)
 }
 
 #### end of pkgconf-funcs
 
 myname=${0##*/}
 if [ $myname = gpgrt-config ]; then
   myname="gpg-error-config"
 fi
 
 usage()
 {
     cat <<EOF
 Usage: $myname [OPTIONS]
 Options:
         [--mt]       (must be the first option)
 	[--prefix]
 	[--exec-prefix]
 	[--version]
 	[--libs]
 	[--cflags]
 EOF
     exit $1
 }
 
 if test $# -eq 0; then
     usage 1 1>&2
 fi
 
 if [ "$1" != "--mt" ]; then
     mt=no
 else
     # In future, use --variable=mtcflags or --variable=mtlibs
     mt=yes
     shift
 fi
 
 modules=""
 output_var=""
 output_attr=""
 opt_cflags=no
 opt_libs=no
 output=""
 delimiter=" "
 
 while test $# -gt 0; do
     case $1 in
 	--prefix)
 	    # In future, use --variable=prefix instead.
 	    output_var=prefix
 	    ;;
 	--exec-prefix)
 	    # In future, use --variable=exec_prefix instead.
 	    output_var=exec_prefix
 	    ;;
 	--version)
 	    # In future, use --modversion instead.
 	    output_attr=Version
 	    delimiter="
 "
 	    ;;
 	--modversion)
 	    output_attr=Version
 	    delimiter="
 "
 	    ;;
 	--cflags)
 	    opt_cflags=yes
 	    ;;
 	--libs)
 	    opt_libs=yes
 	    ;;
 	--variable=*)
 	    output_var=${1#*=}
 	    ;;
 	--host)
 	    # In future, use --variable=host instead.
 	    output_var=host
 	    ;;
 	--help)
 	    usage 0
 	    ;;
 	*)
 	    modules="$modules $1"
 	    ;;
     esac
     shift
 done
 
 if [ $myname = "gpg-error-config" -a -z "$modules" ]; then
     read_config_file ${myname%-config} $PKG_CONFIG_PATH
     if [ -n "$output_var" ]; then
 	output="$output${output:+ }$(get_var $output_var)"
     elif [ -n "$output_attr" ]; then
 	output="$output${output:+ }$(get_attr $output_attr)"
     else
 	cflags="$(get_attr Cflags)"
 	libs="$(get_attr Libs)"
 
 	mtcflags="$(get_var mtcflags)"
 	mtlibs="$(get_var mtlibs)"
     fi
 
     requires="$(get_attr Requires)"
     cleanup_vars_attrs
-    pkg_list=$(all_required_config_files $requires)
+    all_required_config_files $requires
 else
     if [ -z "$modules" ]; then
 	modules=${myname%-config}
     fi
     cflags=""
     libs=""
-    pkg_list=$(all_required_config_files $modules)
+    all_required_config_files $modules
 fi
 
 for p in $pkg_list; do
     read_config_file $p $PKG_CONFIG_PATH
     if [ -n "$output_var" ]; then
 	output="$output${output:+$delimiter}$(get_var $output_var)"
     elif [ -n "$output_attr" ]; then
 	output="$output${output:+$delimiter}$(get_attr $output_attr)"
     else
 	cflags="$cflags${cflags:+ }$(get_attr Cflags)"
 	libs="$libs${libs:+ }$(get_attr Libs)"
     fi
     cleanup_vars_attrs
 done
 
 if [ -z "$output_var" -a -z "$output_attr" ]; then
     if [ $opt_cflags = yes ]; then
-	output="$output $(list_only_once $cflags)"
+	output="$output${output:+ }$(list_only_once $cflags)"
 	# Backward compatibility to old gpg-error-config
 	if [ $mt = yes ]; then
 	    output="$output $mtcflags"
 	fi
     fi
     if [ $opt_libs = yes ]; then
-	output="$output $(list_only_once_for_libs $libs)"
+	output="$output${output:+ }$(list_only_once_for_libs $libs)"
 	# Backward compatibility to old gpg-error-config
 	if [ $mt = yes ]; then
 	    output="$output $mtlibs"
 	fi
     fi
 fi
 
 echo "$output"