Allow PKG_CHECK_MODULES in configure.ac to be commented out easily

(Cherry-pick commits 3d34335, fbb22e9 from 'master' branch.)

* configure.ac [$with_libatomic_ops!=no && $THREADS!=none]
(missing_libatomic_ops): Set to true (before PKG_CHECK_MODULES).
* configure.ac [$missing_libatomic_ops] (PKG_CHECK_MODULES): Set
missing_libatomic_ops back to false if atomic_ops module is not found;
add comment (about pkg-config and the possibility to comment out
PKG_CHECK_MODULES).

diff --git a/configure.ac b/configure.ac
index 7e120f26cabd74215c22d90725338e17ded6ab02..4df809001b2a7beac8e28da73a77357cab258042 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -947,14 +947,21 @@ AC_ARG_WITH([libatomic-ops],
                     [Use an external libatomic_ops? (default: check)])],
     [], [with_libatomic_ops=check])
 
-# Check for an external libatomic_ops if the answer was yes or check.  If not
-# found, fail on yes, and convert check to no.
-# Note: "syntax error near unexpected token ATOMIC_OPS" reported by configure
-# means Autotools pkg.m4 file was not found during aclocal.m4 generation.
+# Check for an external libatomic_ops if the above answer is "yes" or "check".
+# If not found, fail on "yes", and convert "check" to "no".
+# First, check that libatomic_ops usage is not disabled explicitly.
 missing_libatomic_ops=false
 AS_IF([test x"$with_libatomic_ops" != xno -a x"$THREADS" != xnone],
-  [ PKG_CHECK_MODULES([ATOMIC_OPS], [atomic_ops], [],
-                      [ missing_libatomic_ops=true ]) ])
+  [ missing_libatomic_ops=true ])
+
+# Note: "syntax error near unexpected token ATOMIC_OPS" reported by configure
+# means Autotools pkg.m4 file was not found during aclocal.m4 generation;
+# in this case, most probably, you should run pkg-config once before running
+# autogen.sh (autoreconf); alternatively, comment out the following 3 lines.
+AS_IF([test x$missing_libatomic_ops = xtrue],
+  [ PKG_CHECK_MODULES([ATOMIC_OPS], [atomic_ops],
+    [ missing_libatomic_ops=false ], [ [] ]) ])
+
 # Retry with AC_CHECK_HEADER if PKG_CHECK_MODULES failed.
 AS_IF([test x$missing_libatomic_ops = xtrue],
       [ AC_CHECK_HEADER([atomic_ops.h], [missing_libatomic_ops=false]) ])