select: enhance test

[gnulib.git] / m4 / fabsl.m4

diff --git a/m4/fabsl.m4 b/m4/fabsl.m4
index fa4825b..530a13c 100644 (file)
--- a/m4/fabsl.m4
+++ b/m4/fabsl.m4
@@ -1,4 +1,4 @@
-# fabsl.m4 serial 1
+# fabsl.m4 serial 2
 dnl Copyright (C) 2011-2012 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -9,6 +9,9 @@ AC_DEFUN([gl_FUNC_FABSL],
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
   AC_REQUIRE([gl_LONG_DOUBLE_VS_DOUBLE])
 
+  dnl Persuade glibc <math.h> to declare fabsl().
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+
   dnl Determine FABSL_LIBM.
   gl_MATHFUNC([fabsl], [long double], [(long double)])
   if test $gl_cv_func_fabsl_no_libm = yes \