>From a2abacb8133f07c9aa629db03a8e9008d0d15931 Mon Sep 17 00:00:00 2001
From: Assaf Gordon <address@hidden>
Date: Tue, 8 Sep 2015 19:43:32 -0400
Subject: [PATCH] ceill: detect buggy OpenBSD implementation

* m4/ceill.m4: detect buggy openBSD implementation which returns zero
  for small values. discussed here:
  http://lists.gnu.org/archive/html/bug-gnulib/2015-08/msg00010.html
---
 m4/ceill.m4 | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/m4/ceill.m4 b/m4/ceill.m4
index 51c0c56..756d29a 100644
--- a/m4/ceill.m4
+++ b/m4/ceill.m4
@@ -69,6 +69,31 @@ int main (int argc, char *argv[])
   else
     HAVE_DECL_CEILL=0
   fi
+  dnl On OpenBSD5.6 the system's native ceill() is buggy:
+  dnl it returns '0' for small values. Test for this anomaly.
+  if test $REPLACE_CEILL = 0 ; then
+    AC_CACHE_CHECK([whether ceill() breaks with small values],
+        [gl_cv_func_ceill_buggy],
+        [
+          save_LIBS="$LIBS"
+          LIBS="$CEILL_LIBM"
+          AC_RUN_IFELSE(
+           [AC_LANG_PROGRAM(
+             [[#include <math.h>
+long double d = 0.3L;]],
+             [[return (!(ceill (d) == 1)); ]])],
+             [gl_cv_func_ceill_buggy=no], [gl_cv_func_ceill_buggy=yes],
+             [case $host_os in
+                openbsd*) gl_cv_func_ceill_buggy="guessing yes";;
+                *) gl_cv_func_ceill_buggy="guessing no";;
+              esac])
+          LIBS="$save_LIBS"
+        ])
+    case "$gl_cv_func_ceill_buggy" in
+      *yes)
+        REPLACE_CEILL=1 ;;
+    esac
+  fi
   if test $HAVE_DECL_CEILL = 0 || test $REPLACE_CEILL = 1; then
     dnl Find libraries needed to link lib/ceill.c.
     if test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 1; then
-- 
1.9.1