+ m4_ifdef([gl_FUNC_EXP2L_IEEE], [
+ if test $gl_exp2l_required = ieee && test $REPLACE_EXP2L = 0; then
+ AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+ AC_CACHE_CHECK([whether exp2l works according to ISO C 99 with IEC 60559],
+ [gl_cv_func_exp2l_ieee],
+ [
+ save_LIBS="$LIBS"
+ LIBS="$LIBS $EXP2L_LIBM"
+ AC_RUN_IFELSE(
+ [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+#undef exp2l
+extern
+#ifdef __cplusplus
+"C"
+#endif
+long double exp2l (long double);
+static long double dummy (long double x) { return 0; }
+static long double zero;
+int main (int argc, char *argv[])
+{
+ long double (*my_exp2l) (long double) = argc ? exp2l : dummy;
+ int result = 0;
+ /* This test fails on OpenBSD 4.9, where exp2l(NaN) = 0.0. */
+ if (exp2l (zero / zero) == 0.0L)
+ result |= 1;
+ /* This test fails on IRIX 6.5, where exp2l(-Inf) = 1.0. */
+ if (!(exp2l (-1.0L / zero) == 0.0L))
+ result |= 2;
+ return result;
+}
+ ]])],
+ [gl_cv_func_exp2l_ieee=yes],
+ [gl_cv_func_exp2l_ieee=no],
+ [case "$host_os" in
+ # Guess yes on glibc systems.
+ *-gnu*) gl_cv_func_exp2l_ieee="guessing yes" ;;
+ # If we don't know, assume the worst.
+ *) gl_cv_func_exp2l_ieee="guessing no" ;;
+ esac
+ ])
+ LIBS="$save_LIBS"
+ ])
+ case "$gl_cv_func_exp2l_ieee" in
+ *yes) ;;
+ *) REPLACE_EXP2L=1 ;;
+ esac
+ fi
+ ])