cbrtl-ieee: Work around test failure on IRIX 6.5.

* m4/cbrtl-ieee.m4: New file.
* m4/cbrtl.m4 (gl_FUNC_CBRTL): If gl_FUNC_CBRTL_IEEE is present,
test whether cbrtl works with a minus zero argument. Replace it if not.
* lib/math.in.h (cbrtl): Override if REPLACE_CBRTL is 1.
* m4/math_h.m4 (gl_MATH_H_DEFAULTS): Initialize REPLACE_CBRTL.
* modules/math (Makefile.am): Substitute REPLACE_CBRTL.
* modules/cbrtl (configure.ac): Consider REPLACE_CBRTL.
(Depends-on): Update conditions.
* modules/cbrtl-ieee (Files): Add m4/cbrtl-ieee.m4, m4/minus-zero.m4,
m4/signbit.m4.
(configure.ac): Invoke gl_FUNC_CBRTL_IEEE.
* lib/cbrtl.c (cbrtl) [IRIX]: Avoid an unnecessary addition.
* doc/posix-functions/cbrtl.texi: Mention the cbrtl-ieee module.

1 files changed, 48 insertions, 1 deletions

diff --git a/m4/cbrtl.m4 b/m4/cbrtl.m4
index 3f02abcc30..f40a1c0d67 100644
--- a/m4/cbrtl.m4
+++ b/m4/cbrtl.m4
@@ -1,4 +1,4 @@
-# cbrtl.m4 serial 1
+# cbrtl.m4 serial 2
 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,
@@ -6,6 +6,7 @@ dnl with or without modifications, as long as this notice is preserved.
 
 AC_DEFUN([gl_FUNC_CBRTL],
 [
+  m4_divert_text([DEFAULTS], [gl_cbrtl_required=plain])
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
   AC_REQUIRE([gl_LONG_DOUBLE_VS_DOUBLE])
   AC_REQUIRE([gl_FUNC_CBRT])
@@ -21,9 +22,55 @@ AC_DEFUN([gl_FUNC_CBRTL],
     dnl Also check whether it's declared.
     dnl IRIX 6.5 has cbrtl() in libm but doesn't declare it in <math.h>.
     AC_CHECK_DECL([cbrtl], , [HAVE_DECL_CBRTL=0], [[#include <math.h>]])
+    m4_ifdef([gl_FUNC_CBRTL_IEEE], [
+      if test $gl_cbrtl_required = ieee && test $REPLACE_CBRTL = 0; then
+        AC_CACHE_CHECK([whether cbrtl works according to ISO C 99 with IEC 60559],
+          [gl_cv_func_cbrtl_ieee],
+          [
+            save_LIBS="$LIBS"
+            LIBS="$LIBS $CBRTL_LIBM"
+            AC_RUN_IFELSE(
+              [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+]gl_LONG_DOUBLE_MINUS_ZERO_CODE[
+]gl_LONG_DOUBLE_SIGNBIT_CODE[
+static long double dummy (long double x) { return 0; }
+int main (int argc, char *argv[])
+{
+  extern
+  #ifdef __cplusplus
+  "C"
+  #endif
+  long double cbrtl (long double);
+  long double (*my_cbrtl) (long double) = argc ? cbrtl : dummy;
+  long double f;
+  /* Test cbrtl(-0.0).
+     This test fails on IRIX 6.5.  */
+  f = my_cbrtl (minus_zerol);
+  if (!(f == 0.0L) || (signbitl (minus_zerol) && !signbitl (f)))
+    return 1;
+  return 0;
+}
+              ]])],
+              [gl_cv_func_cbrtl_ieee=yes],
+              [gl_cv_func_cbrtl_ieee=no],
+              [gl_cv_func_cbrtl_ieee="guessing no"])
+            LIBS="$save_LIBS"
+          ])
+        case "$gl_cv_func_cbrtl_ieee" in
+          *yes) ;;
+          *) REPLACE_CBRTL=1 ;;
+        esac
+      fi
+    ])
   else
     HAVE_CBRTL=0
     HAVE_DECL_CBRTL=0
+  fi
+  if test $HAVE_CBRTL = 0 || test $REPLACE_CBRTL = 1; then
     dnl Find libraries needed to link lib/cbrtl.c.
     if test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 1; then
       CBRTL_LIBM="$CBRT_LIBM"