Do not use PKG_CHECK_MODULES in configure

Issue #200 (bdwgc).

Presence of libatomic_ops is now detected only by checking the
installed headers, but libatomic_ops is no longer needed for most of
the clients which have atomic intrinsics support by the compiler.

* README.md (Installation and Portability): Remove information about
"syntax error near unexpected token ATOMIC_OPS".
* autogen.sh: Update comment removing pkg-config from the requirements.
* configure.ac (PKG_CHECK_MODULES(ATOMIC_OPS)): Comment out; update the
comment.

3 files changed, 8 insertions, 13 deletions

diff --git a/README.md b/README.md
index c25e82a0..6b4ae5cc 100644
--- a/README.md
+++ b/README.md
@@ -192,10 +192,6 @@ build of `master` branch of the collector could look like:
 Cloning of `libatomic_ops` is now optional provided the compiler supports
 atomic intrinsics.
 
-If you are getting "syntax error near unexpected token ATOMIC_OPS" during
-configure execution, this means pkg.m4 cannot be found, most probably
-you should run `pkg-config` once before running `./autogen.sh` (autoreconf).
-
 Below we focus on the collector build using classic makefile.
 For the Makefile.direct-based process, typing `make check` instead of `make`
 will automatically build the collector and then run `setjmp_test` and `gctest`.
diff --git a/autogen.sh b/autogen.sh
index 8a614f91..c1500b2d 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -5,8 +5,8 @@ set -e
 # config.h.in, Makefile.in, etc.) missing in the source repository.
 #
 # If you compile from a distribution tarball, you can skip this.  Otherwise,
-# make sure that you have Autoconf, Automake, Libtool, and pkg-config
-# installed on your system, and that the corresponding *.m4 files are visible
+# make sure that you have Autoconf, Automake and Libtool installed
+# on your system, and that the corresponding *.m4 files are visible
 # to the aclocal.  The latter can be achieved by using packages shipped by
 # your OS, or by installing custom versions of all four packages to the same
 # prefix.  Otherwise, you may need to invoke autoreconf with the appropriate
diff --git a/configure.ac b/configure.ac
index 501be32d..3170309d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1018,13 +1018,12 @@ missing_libatomic_ops=false
 AS_IF([test x"$with_libatomic_ops" != xno -a x"$with_libatomic_ops" != xnone],
   [ missing_libatomic_ops=true ])
 
-dnl Note: "syntax error near unexpected token ATOMIC_OPS" reported by configure
-dnl means Autotools pkg.m4 file was not found during aclocal.m4 generation;
-dnl in this case, most probably, you should run pkg-config once before running
-dnl autogen.sh (autoreconf); alternatively, comment out the following 3 lines.
-AS_IF([test x$missing_libatomic_ops = xtrue],
-  [ PKG_CHECK_MODULES([ATOMIC_OPS], [atomic_ops],
-    [ missing_libatomic_ops=false ], [ [] ]) ])
+dnl To avoid "syntax error near unexpected token ATOMIC_OPS" configure error
+dnl observed by some clients, the following 3 code lines are commented out:
+dnl
+dnl AS_IF([test x$missing_libatomic_ops = xtrue],
+dnl  [ PKG_CHECK_MODULES([ATOMIC_OPS], [atomic_ops],
+dnl    [ missing_libatomic_ops=false ], [ [] ]) ])
 
 dnl Retry with AC_CHECK_HEADER if PKG_CHECK_MODULES failed.
 AS_IF([test x$missing_libatomic_ops = xtrue],