+ if test $ac_cv_func_log1p = yes; then
+ :
+ m4_ifdef([gl_FUNC_LOG1P_IEEE], [
+ if test $gl_log1p_required = ieee && test $REPLACE_LOG1P = 0; then
+ AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+ AC_CACHE_CHECK([whether log1p works according to ISO C 99 with IEC 60559],
+ [gl_cv_func_log1p_ieee],
+ [
+ save_LIBS="$LIBS"
+ LIBS="$LIBS $LOG1P_LIBM"
+ AC_RUN_IFELSE(
+ [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+]gl_DOUBLE_MINUS_ZERO_CODE[
+]gl_DOUBLE_SIGNBIT_CODE[
+static double dummy (double x) { return 0; }
+int main (int argc, char *argv[])
+{
+ double (*my_log1p) (double) = argc ? log1p : dummy;
+ /* This test fails on AIX, HP-UX 11. */
+ double y = my_log1p (minus_zerod);
+ if (!(y == 0.0) || (signbitd (minus_zerod) && !signbitd (y)))
+ return 1;
+ return 0;
+}
+ ]])],
+ [gl_cv_func_log1p_ieee=yes],
+ [gl_cv_func_log1p_ieee=no],
+ [case "$host_os" in
+ # Guess yes on glibc systems.
+ *-gnu*) gl_cv_func_log1p_ieee="guessing yes" ;;
+ # If we don't know, assume the worst.
+ *) gl_cv_func_log1p_ieee="guessing no" ;;
+ esac
+ ])
+ LIBS="$save_LIBS"
+ ])
+ case "$gl_cv_func_log1p_ieee" in
+ *yes) ;;
+ *) REPLACE_LOG1P=1 ;;
+ esac
+ fi
+ ])
+ else