build: check if pkg-config is correctly installed in ./autogen.sh

Absence of pkg-config leads to some odd messages:

    configure.ac:27: error: possibly undefined macro: AC_SUBST
          If this token and others are legitimate, please use m4_pattern_allow.
          See the Autoconf documentation.
    configure.ac:163: error: possibly undefined macro: AC_MSG_FAILURE
    configure:21413: error: possibly undefined macro: AC_MSG_CHECKING
    configure:21418: error: possibly undefined macro: AC_TRY_LINK
    configure:21423: error: possibly undefined macro: AC_MSG_RESULT
    configure:21432: error: possibly undefined macro: AC_MSG_NOTICE
    configure:21894: error: possibly undefined macro: AC_PATH_TOOL
    configure:21896: error: possibly undefined macro: AC_MSG_ERROR
    configure:21975: error: possibly undefined macro: AC_DEFINE_UNQUOTED

We try to detect this situation by looking for `PKG_CHECK_MODULES` macro
in `aclocal.m4`. If not present, we issue some useful tips, like
installing the package or telling aclocal the location of
`pkg.m4` (mostly for OSX users).

diff --git a/autogen.sh b/autogen.sh
index 78e5d82b1bfc1aa8dce68a395a3127aabd07563c..bc63a810d8f2a4853c3bee61bf940f7549e9217c 100755 (executable)
--- a/autogen.sh
+++ b/autogen.sh
@@ -36,6 +36,32 @@ check_command "$AUTOCONF"
 check_command "$AUTOHEADER"
 check_command "$AUTOMAKE"
 
+# Absence of pkg-config or misconfiguration can make some odd error
+# messages, we check if it is installed correctly. See:
+#  https://blogs.oracle.com/mandy/entry/autoconf_weirdness
+#
+# We cannot just check for pkg-config command, we need to check for
+# PKG_* macros. The pkg-config command can be defined in ./configure,
+# we cannot tell anything when not present.
+check_pkg_config() {
+    grep -q '^AC_DEFUN.*PKG_CHECK_MODULES' aclocal.m4 || {
+        cat <<EOF >&2
+autogen.sh: could not find PKG_CHECK_MODULES macro.
+
+  Either pkg-config is not installed on your system or
+  \`pkg.m4' is missing or not found by aclocal.
+
+  If \`pkg.m4' is installed at an unusual location, re-run
+  \`autogen.sh' by setting \`ACLOCAL_FLAGS':
+
+    ACLOCAL_FLAGS="-I <prefix>/share/aclocal" ./autogen.sh
+
+EOF
+        exit 1
+    }
+}
+
+
 echo "autogen.sh: start libtoolize to get ltmain.sh"
 ${LIBTOOLIZE} --copy --force
 echo "autogen.sh: reconfigure with autoreconf"
@@ -45,9 +71,10 @@ ${AUTORECONF} -vif -I m4 || {
         [ -d "$dir" ] || continue
         [ -f "$dir"/configure.ac ] || [ -f "$dir"/configure.in ] || continue
        echo "autogen.sh: configure `basename $dir`"
-       (cd "$dir" && ${ACLOCAL} -I m4)
+       (cd "$dir" && ${ACLOCAL} -I m4 ${ACLOCAL_FLAGS})
+        (cd "$dir" && check_pkg_config)
        (cd "$dir" && ${LIBTOOLIZE} --automake --copy --force)
-       (cd "$dir" && ${ACLOCAL} -I m4)
+       (cd "$dir" && ${ACLOCAL} -I m4 ${ACLOCAL_FLAGS})
        (cd "$dir" && ${AUTOCONF} --force)
        (cd "$dir" && ${AUTOHEADER})
        (cd "$dir" && ${AUTOMAKE} --add-missing --copy --force-missing)