submitting a patch for ax_openmp.m4

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Hello,

attached is a patch to allow testing for OpenMP support on recent
Darwin/macOS systems with Apple's clang (this needs adding a new option,
with a space in it...)

Also pasted below, in case attachments aren't processed here.
Not sure whether "series" should be bumped to 15.

Best,
Dima Pasechnik
https://pasechnik.info/dima


From 151639ceaf8b939a332f7386256d78895ee7f144 Mon Sep 17 00:00:00 2001
From: Dima Pasechnik <[email protected]>
Date: Mon, 16 Feb 2026 13:40:53 -0600
Subject: [PATCH] test for OpenMP support with Darwin (Apple) clang

---
 m4/ax_openmp.m4 | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/m4/ax_openmp.m4 b/m4/ax_openmp.m4
index 59b5c27..4baa83c 100644
--- a/m4/ax_openmp.m4
+++ b/m4/ax_openmp.m4
@@ -78,12 +78,15 @@ ax_cv_[]_AC_LANG_ABBREV[]_openmp=unknown
 #                -qopenmp (icc>=15), -openmp (icc),
 #                -xopenmp (Sun), -omp (Tru64),
 #                -qsmp=omp (AIX),
+#                -Xpreprocessor -fopenmp (Darwin's clang),
 #                none
-ax_openmp_flags="-fopenmp -openmp -qopenmp -mp -xopenmp -omp -qsmp=omp none"
+ax_openmp_flags="-fopenmp:-openmp:-Xpreprocessor -fopenmp:-qopenmp:-mp:-xopenmp:-omp:-qsmp=omp:none"
 if test "x$OPENMP_[]_AC_LANG_PREFIX[]FLAGS" != x; then
-  ax_openmp_flags="$OPENMP_[]_AC_LANG_PREFIX[]FLAGS $ax_openmp_flags"
+  ax_openmp_flags="$OPENMP_[]_AC_LANG_PREFIX[]FLAGS:$ax_openmp_flags"
 fi
+ac_save_ax_openmp_IFS="$IFS"; IFS=":"
 for ax_openmp_flag in $ax_openmp_flags; do
+  IFS="$ac_save_ax_openmp_IFS"
   case $ax_openmp_flag in
     none) []_AC_LANG_PREFIX[]FLAGS=$save[]_AC_LANG_PREFIX[] ;;
     *) []_AC_LANG_PREFIX[]FLAGS="$save[]_AC_LANG_PREFIX[]FLAGS $ax_openmp_flag" ;;
@@ -109,7 +112,11 @@ main(void)
   return 0;
 }
 ]])],[ax_cv_[]_AC_LANG_ABBREV[]_openmp=$ax_openmp_flag; break],[])
+ac_save_ax_openmp_IFS="$IFS"; IFS=":"
 done
+
+IFS="$ac_save_ax_openmp_IFS"
+
 []_AC_LANG_PREFIX[]FLAGS=$save[]_AC_LANG_PREFIX[]FLAGS
 ])
 if test "x$ax_cv_[]_AC_LANG_ABBREV[]_openmp" = "xunknown"; then
-- 
2.52.0



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	filename=0001-test-for-OpenMP-support-with-Darwin-Apple-clang.patch

From 151639ceaf8b939a332f7386256d78895ee7f144 Mon Sep 17 00:00:00 2001
From: Dima Pasechnik <[email protected]>
Date: Mon, 16 Feb 2026 13:40:53 -0600
Subject: [PATCH] test for OpenMP support with Darwin (Apple) clang

---
 m4/ax_openmp.m4 | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/m4/ax_openmp.m4 b/m4/ax_openmp.m4
index 59b5c27..4baa83c 100644
--- a/m4/ax_openmp.m4
+++ b/m4/ax_openmp.m4
@@ -78,12 +78,15 @@ ax_cv_[]_AC_LANG_ABBREV[]_openmp=unknown
 #                -qopenmp (icc>=15), -openmp (icc),
 #                -xopenmp (Sun), -omp (Tru64),
 #                -qsmp=omp (AIX),
+#                -Xpreprocessor -fopenmp (Darwin's clang),
 #                none
-ax_openmp_flags="-fopenmp -openmp -qopenmp -mp -xopenmp -omp -qsmp=omp none"
+ax_openmp_flags="-fopenmp:-openmp:-Xpreprocessor -fopenmp:-qopenmp:-mp:-xopenmp:-omp:-qsmp=omp:none"
 if test "x$OPENMP_[]_AC_LANG_PREFIX[]FLAGS" != x; then
-  ax_openmp_flags="$OPENMP_[]_AC_LANG_PREFIX[]FLAGS $ax_openmp_flags"
+  ax_openmp_flags="$OPENMP_[]_AC_LANG_PREFIX[]FLAGS:$ax_openmp_flags"
 fi
+ac_save_ax_openmp_IFS="$IFS"; IFS=":"
 for ax_openmp_flag in $ax_openmp_flags; do
+  IFS="$ac_save_ax_openmp_IFS"
   case $ax_openmp_flag in
     none) []_AC_LANG_PREFIX[]FLAGS=$save[]_AC_LANG_PREFIX[] ;;
     *) []_AC_LANG_PREFIX[]FLAGS="$save[]_AC_LANG_PREFIX[]FLAGS $ax_openmp_flag" ;;
@@ -109,7 +112,11 @@ main(void)
   return 0;
 }
 ]])],[ax_cv_[]_AC_LANG_ABBREV[]_openmp=$ax_openmp_flag; break],[])
+ac_save_ax_openmp_IFS="$IFS"; IFS=":"
 done
+
+IFS="$ac_save_ax_openmp_IFS"
+
 []_AC_LANG_PREFIX[]FLAGS=$save[]_AC_LANG_PREFIX[]FLAGS
 ])
 if test "x$ax_cv_[]_AC_LANG_ABBREV[]_openmp" = "xunknown"; then
-- 
2.52.0


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