math: Ensure declarations of math functions.

[gnulib.git] / m4 / hypotl.m4

diff --git a/m4/hypotl.m4 b/m4/hypotl.m4
index 424e0a1..e7b0eb2 100644 (file)
--- a/m4/hypotl.m4
+++ b/m4/hypotl.m4
@@ -1,4 +1,4 @@
-# hypotl.m4 serial 2
+# hypotl.m4 serial 3
 dnl Copyright (C) 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,
@@ -10,6 +10,9 @@ AC_DEFUN([gl_FUNC_HYPOTL],
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
   AC_REQUIRE([gl_FUNC_HYPOT])
 
+  dnl Persuade glibc <math.h> to declare hypotl().
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+
   dnl Test whether hypotl() exists. Assume that hypotl(), if it exists, is
   dnl defined in the same library as hypot().
   save_LIBS="$LIBS"