libimagequant: fix integration

The symbol was being set up in cmake but not on the autotools side.
Clean this up to be like other external libraries.

We need to pull in some openmp logic as it's not uncommon for the lib
to be built with openmp support.  When we test for it, we need to do
so with openmp flags.

Fixes #137.

1 files changed, 119 insertions, 0 deletions

diff --git a/m4/ax_openmp.m4 b/m4/ax_openmp.m4
new file mode 100644
index 0000000..4d5d88b
--- /dev/null
+++ b/m4/ax_openmp.m4
@@ -0,0 +1,119 @@
+# ===========================================================================
+#         http://www.gnu.org/software/autoconf-archive/ax_openmp.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_OPENMP([ACTION-IF-FOUND[, ACTION-IF-NOT-FOUND]])
+#
+# DESCRIPTION
+#
+#   This macro tries to find out how to compile programs that use OpenMP a
+#   standard API and set of compiler directives for parallel programming
+#   (see http://www-unix.mcs/)
+#
+#   On success, it sets the OPENMP_CFLAGS/OPENMP_CXXFLAGS/OPENMP_F77FLAGS
+#   output variable to the flag (e.g. -omp) used both to compile *and* link
+#   OpenMP programs in the current language.
+#
+#   NOTE: You are assumed to not only compile your program with these flags,
+#   but also link it with them as well.
+#
+#   If you want to compile everything with OpenMP, you should set:
+#
+#     CFLAGS="$CFLAGS $OPENMP_CFLAGS"
+#     #OR#  CXXFLAGS="$CXXFLAGS $OPENMP_CXXFLAGS"
+#     #OR#  FFLAGS="$FFLAGS $OPENMP_FFLAGS"
+#
+#   (depending on the selected language).
+#
+#   The user can override the default choice by setting the corresponding
+#   environment variable (e.g. OPENMP_CFLAGS).
+#
+#   ACTION-IF-FOUND is a list of shell commands to run if an OpenMP flag is
+#   found, and ACTION-IF-NOT-FOUND is a list of commands to run it if it is
+#   not found. If ACTION-IF-FOUND is not specified, the default action will
+#   define HAVE_OPENMP.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Steven G. Johnson <stevenj@alum.mit.edu>
+#   Copyright (c) 2015 John W. Peterson <jwpeterson@gmail.com>
+#
+#   This program 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.
+#
+#   This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
+#
+#   As a special exception, the respective Autoconf Macro's copyright owner
+#   gives unlimited permission to copy, distribute and modify the configure
+#   scripts that are the output of Autoconf when processing the Macro. You
+#   need not follow the terms of the GNU General Public License when using
+#   or distributing such scripts, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+#serial 11
+
+AC_DEFUN([AX_OPENMP], [
+AC_PREREQ([2.69]) dnl for _AC_LANG_PREFIX
+
+AC_CACHE_CHECK([for OpenMP flag of _AC_LANG compiler], ax_cv_[]_AC_LANG_ABBREV[]_openmp, [save[]_AC_LANG_PREFIX[]FLAGS=$[]_AC_LANG_PREFIX[]FLAGS
+ax_cv_[]_AC_LANG_ABBREV[]_openmp=unknown
+# Flags to try:  -fopenmp (gcc), -openmp (icc), -mp (SGI & PGI),
+#                -xopenmp (Sun), -omp (Tru64), -qsmp=omp (AIX), none
+ax_openmp_flags="-fopenmp -openmp -mp -xopenmp -omp -qsmp=omp none"
+if test "x$OPENMP_[]_AC_LANG_PREFIX[]FLAGS" != x; then
+  ax_openmp_flags="$OPENMP_[]_AC_LANG_PREFIX[]FLAGS $ax_openmp_flags"
+fi
+for ax_openmp_flag in $ax_openmp_flags; do
+  case $ax_openmp_flag in
+    none) []_AC_LANG_PREFIX[]FLAGS=$save[]_AC_LANG_PREFIX[] ;;
+    *) []_AC_LANG_PREFIX[]FLAGS="$save[]_AC_LANG_PREFIX[]FLAGS $ax_openmp_flag" ;;
+  esac
+  AC_LINK_IFELSE([AC_LANG_SOURCE([[
+@%:@include <omp.h>
+
+static void
+parallel_fill(int * data, int n)
+{
+  int i;
+@%:@pragma omp parallel for
+  for (i = 0; i < n; ++i)
+    data[i] = i;
+}
+
+int
+main()
+{
+  int arr[100000];
+  omp_set_num_threads(2);
+  parallel_fill(arr, 100000);
+  return 0;
+}
+]])],[ax_cv_[]_AC_LANG_ABBREV[]_openmp=$ax_openmp_flag; break],[])
+done
+[]_AC_LANG_PREFIX[]FLAGS=$save[]_AC_LANG_PREFIX[]FLAGS
+])
+if test "x$ax_cv_[]_AC_LANG_ABBREV[]_openmp" = "xunknown"; then
+  m4_default([$2],:)
+else
+  if test "x$ax_cv_[]_AC_LANG_ABBREV[]_openmp" != "xnone"; then
+    OPENMP_[]_AC_LANG_PREFIX[]FLAGS=$ax_cv_[]_AC_LANG_ABBREV[]_openmp
+  fi
+  m4_default([$1], [AC_DEFINE(HAVE_OPENMP,1,[Define if OpenMP is enabled])])
+fi
+])dnl AX_OPENMP