From 80fbaac4cd1930e9545a5d36bf46ae49011d2ce8 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Wed, 17 Feb 2016 13:53:54 -0500
Subject: [PATCH] make configure attempt to catch broken floating point
 CFLAGS/defaults

---
 configure | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/configure b/configure
index 248c4500..779a3ef0 100755
--- a/configure
+++ b/configure
@@ -655,6 +655,16 @@ printf "no\n"
 fail "$0: error: unsupported long double type"
 fi
 
+#
+# Some build systems globally pass in broken CFLAGS like -ffast-math
+# for all packages. On recent GCC we can detect this and error out
+# early rather than producing a seriously-broken math library.
+#
+if trycppif "__FAST_MATH__ || (defined(__GCC_IEC_559) && __GCC_IEC_559==0)" \
+  "$CFLAGS_C99FSE $CPPFLAGS $CFLAGS" ; then
+fail "$0: error: compiler has broken floating point; check CFLAGS"
+fi
+
 printf "creating config.mak... "
 
 cmdline=$(quote "$0")
-- 
2.25.1