Resync config/ from GCC.

config/math.m4

@@ -0,0 +1,50 @@
+dnl GCC_CHECK_LIBM
+dnl
+dnl Check whether -lm is available.  This is a pre-requisite for
+dnl GCC_CHECK_MATH_FUNC so that it will link with -lm.
+AC_DEFUN([GCC_CHECK_LIBM],
+[AC_CHECK_LIB([m],[sin])])
+
+dnl GCC_CHECK_MATH_HEADERS
+dnl
+dnl Check for math.h and complex.h.  This is a pre-requisite for
+dnl GCC_CHECK_MATH_FUNC so that it includes the right headers.
+dnl (Some systems, such as AIX or OpenVMS may define macro for math
+dnl  functions).
+AC_DEFUN([GCC_CHECK_MATH_HEADERS],
+[AC_CHECK_HEADERS_ONCE(math.h complex.h)])
+
+dnl GCC_CHECK_MATH_FUNC([name])
+dnl
+dnl Check whether math function NAME is available on the system (by compiling
+dnl and linking a C program) and run define HAVE_name on success.
+dnl
+dnl Note that OpenVMS system insists on including complex.h before math.h
+AC_DEFUN([GCC_CHECK_MATH_FUNC],
+[
+  AC_REQUIRE([GCC_CHECK_LIBM])
+  AC_REQUIRE([GCC_CHECK_MATH_HEADERS])
+  AC_CACHE_CHECK([for $1], [gcc_cv_math_func_$1],
+		 [AC_LINK_IFELSE([
+#ifdef HAVE_COMPLEX_H
+#include <complex.h>
+#endif
+#ifdef HAVE_MATH_H
+#include <math.h>
+#endif
+
+int (*ptr)() = (int (*)())$1;
+
+int
+main ()
+{
+  return 0;
+}
+],
+[gcc_cv_math_func_$1=yes],
+[gcc_cv_math_func_$1=no])])
+  if test $gcc_cv_math_func_$1 = yes; then
+    AC_DEFINE_UNQUOTED(AS_TR_CPP(HAVE_$1),[1],
+                       [Define to 1 if you have the `$1' function.])
+  fi
+])