From 0567678636c46265af80b3e5be463539dd84b893 Mon Sep 17 00:00:00 2001
From: Sergey B Kirpichev <skirpichev@gmail.com>
Date: Wed, 2 Sep 2026 13:06:42 +0300
Subject: [PATCH 1/2] gh-153740: refine test for _Float16 (check support from
 libm)

---
 configure    | 4 +++-
 configure.ac | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index e0ad04b036aeb13..dbc71e5b27d64f6 100755
--- a/configure
+++ b/configure
@@ -16745,12 +16745,14 @@ else case e in #(
   e) cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+#include <math.h>
 int main(void)
 {
     _Float16 val = 1.0f16;
+    int test = !isfinite(val) || isinf(val) || isnan(val);
     double d = 3.14;
     val = d;
-    return 0;
+    return test;
 }
 
 _ACEOF
diff --git a/configure.ac b/configure.ac
index 2b8a5b052878c91..e367d2dd71682a6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4474,12 +4474,14 @@ AC_CACHE_CHECK([for _Float16 support], [ac_cv_float16_supported],
 WITH_SAVE_ENV([
 CFLAGS="$CFLAGS -O0"
 AC_RUN_IFELSE([AC_LANG_SOURCE([[
+#include <math.h>
 int main(void)
 {
     _Float16 val = 1.0f16;
+    int test = !isfinite(val) || isinf(val) || isnan(val);
     double d = 3.14;
     val = d;
-    return 0;
+    return test;
 }
 ]])], [ac_cv_float16_supported=yes],
 [ac_cv_float16_supported=no],

From 8daf2de17e5d8b27422326049459ba95fe7117e2 Mon Sep 17 00:00:00 2001
From: Sergey B Kirpichev <skirpichev@gmail.com>
Date: Wed, 2 Sep 2026 15:58:26 +0300
Subject: [PATCH 2/2] + comment on test

---
 configure    | 2 +-
 configure.ac | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index dbc71e5b27d64f6..a2ca40de07d54ec 100755
--- a/configure
+++ b/configure
@@ -16749,7 +16749,7 @@ else case e in #(
 int main(void)
 {
     _Float16 val = 1.0f16;
-    int test = !isfinite(val) || isinf(val) || isnan(val);
+    int test = isinf(val) || isnan(val); /* basic support from libm */
     double d = 3.14;
     val = d;
     return test;
diff --git a/configure.ac b/configure.ac
index e367d2dd71682a6..e1333230fefa688 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4478,7 +4478,7 @@ AC_RUN_IFELSE([AC_LANG_SOURCE([[
 int main(void)
 {
     _Float16 val = 1.0f16;
-    int test = !isfinite(val) || isinf(val) || isnan(val);
+    int test = isinf(val) || isnan(val); /* basic support from libm */
     double d = 3.14;
     val = d;
     return test;