Merge remote-tracking branch 'origin/stable-2.0'

Conflicts:
	libguile/numbers.c
	libguile/vm-i-scheme.c

5 files changed, 594 insertions, 1 deletions

diff --git a/m4/copysign.m4 b/m4/copysign.m4
new file mode 100644
index 000000000..382a6c6bb
--- /dev/null
+++ b/m4/copysign.m4
@@ -0,0 +1,19 @@
+# copysign.m4 serial 1
+dnl Copyright (C) 2011-2013 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_COPYSIGN],
+[
+  AC_REQUIRE([gl_MATH_H_DEFAULTS])
+
+  dnl Determine COPYSIGN_LIBM.
+  gl_MATHFUNC([copysign], [double], [(double, double)])
+  if test $gl_cv_func_copysign_no_libm = no \
+     && test $gl_cv_func_copysign_in_libm = no; then
+    HAVE_COPYSIGN=0
+    COPYSIGN_LIBM=
+  fi
+  AC_SUBST([COPYSIGN_LIBM])
+])
diff --git a/m4/gnulib-cache.m4 b/m4/gnulib-cache.m4
index 81e464632..d41ec7b22 100644
--- a/m4/gnulib-cache.m4
+++ b/m4/gnulib-cache.m4
@@ -27,7 +27,7 @@
 
 
 # Specification in the form of a command-line invocation:
-#   gnulib-tool --import --dir=. --local-dir=gnulib-local --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --lgpl=3 --no-conditional-dependencies --libtool --macro-prefix=gl --no-vc-files accept alignof alloca-opt announce-gen autobuild bind byteswap c-strcase canonicalize-lgpl ceil clock-time close connect dirfd duplocale environ extensions flock floor fpieee frexp fstat full-read full-write func gendocs getaddrinfo getlogin getpeername getsockname getsockopt git-version-gen gitlog-to-changelog gnu-web-doc-update gnupload havelib iconv_open-utf inet_ntop inet_pton isinf isnan ldexp lib-symbol-versions lib-symbol-visibility libunistring listen localcharset locale log1p maintainer-makefile malloc-gnu malloca nl_langinfo nproc open pipe-posix pipe2 poll putenv recv recvfrom regex rename select send sendto setenv setsockopt shutdown socket stat-time stdlib strftime striconveh string sys_stat time times trunc verify vsnprintf warnings wchar
+#   gnulib-tool --import --dir=. --local-dir=gnulib-local --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --lgpl=3 --no-conditional-dependencies --libtool --macro-prefix=gl --no-vc-files accept alignof alloca-opt announce-gen autobuild bind byteswap c-strcase canonicalize-lgpl ceil clock-time close connect copysign dirfd duplocale environ extensions flock floor fpieee frexp fstat full-read full-write func gendocs getaddrinfo getlogin getpeername getsockname getsockopt git-version-gen gitlog-to-changelog gnu-web-doc-update gnupload havelib iconv_open-utf inet_ntop inet_pton isfinite isinf isnan ldexp lib-symbol-versions lib-symbol-visibility libunistring listen localcharset locale log1p maintainer-makefile malloc-gnu malloca nl_langinfo nproc open pipe-posix pipe2 poll putenv recv recvfrom regex rename select send sendto setenv setsockopt shutdown socket stat-time stdlib strftime striconveh string sys_stat time times trunc verify vsnprintf warnings wchar
 
 # Specification in the form of a few gnulib-tool.m4 macro invocations:
 gl_LOCAL_DIR([gnulib-local])
@@ -45,6 +45,7 @@ gl_MODULES([
   clock-time
   close
   connect
+  copysign
   dirfd
   duplocale
   environ
@@ -71,6 +72,7 @@ gl_MODULES([
   iconv_open-utf
   inet_ntop
   inet_pton
+  isfinite
   isinf
   isnan
   largefile
diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index 55c003a58..8a1b80175 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -61,6 +61,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module close:
   # Code from module configmake:
   # Code from module connect:
+  # Code from module copysign:
   # Code from module dirent:
   # Code from module dirfd:
   # Code from module dirname-lgpl:
@@ -108,12 +109,15 @@ AC_DEFUN([gl_EARLY],
   # Code from module inet_ntop:
   # Code from module inet_pton:
   # Code from module inline:
+  # Code from module isfinite:
   # Code from module isinf:
   # Code from module isnan:
   # Code from module isnand:
   # Code from module isnand-nolibm:
   # Code from module isnanf:
+  # Code from module isnanf-nolibm:
   # Code from module isnanl:
+  # Code from module isnanl-nolibm:
   # Code from module langinfo:
   # Code from module largefile:
   AC_REQUIRE([AC_SYS_LARGEFILE])
@@ -172,6 +176,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module setsockopt:
   # Code from module shutdown:
   # Code from module signal-h:
+  # Code from module signbit:
   # Code from module size_max:
   # Code from module snippet/_Noreturn:
   # Code from module snippet/arg-nonnull:
@@ -292,6 +297,11 @@ AC_SUBST([LTALLOCA])
     AC_LIBOBJ([connect])
   fi
   gl_SYS_SOCKET_MODULE_INDICATOR([connect])
+  gl_FUNC_COPYSIGN
+  if test $HAVE_COPYSIGN = 0; then
+    AC_LIBOBJ([copysign])
+  fi
+  gl_MATH_MODULE_INDICATOR([copysign])
   gl_DIRENT_H
   gl_FUNC_DIRFD
   if test $ac_cv_func_dirfd = no && test $gl_cv_func_dirfd_macro = no; then
@@ -415,6 +425,11 @@ AC_SUBST([LTALLOCA])
   fi
   gl_ARPA_INET_MODULE_INDICATOR([inet_pton])
   gl_INLINE
+  gl_ISFINITE
+  if test $REPLACE_ISFINITE = 1; then
+    AC_LIBOBJ([isfinite])
+  fi
+  gl_MATH_MODULE_INDICATOR([isfinite])
   gl_ISINF
   if test $REPLACE_ISINF = 1; then
     AC_LIBOBJ([isinf])
@@ -445,6 +460,11 @@ AC_SUBST([LTALLOCA])
     gl_PREREQ_ISNANF
   fi
   gl_MATH_MODULE_INDICATOR([isnanf])
+  gl_FUNC_ISNANF_NO_LIBM
+  if test $gl_func_isnanf_no_libm != yes; then
+    AC_LIBOBJ([isnanf])
+    gl_PREREQ_ISNANF
+  fi
   gl_FUNC_ISNANL
   m4_ifdef([gl_ISNAN], [
     AC_REQUIRE([gl_ISNAN])
@@ -454,6 +474,11 @@ AC_SUBST([LTALLOCA])
     gl_PREREQ_ISNANL
   fi
   gl_MATH_MODULE_INDICATOR([isnanl])
+  gl_FUNC_ISNANL_NO_LIBM
+  if test $gl_func_isnanl_no_libm != yes; then
+    AC_LIBOBJ([isnanl])
+    gl_PREREQ_ISNANL
+  fi
   gl_LANGINFO_H
   AC_REQUIRE([gl_LARGEFILE])
   gl_FUNC_LDEXP
@@ -656,6 +681,13 @@ AC_SUBST([LTALLOCA])
   fi
   gl_SYS_SOCKET_MODULE_INDICATOR([shutdown])
   gl_SIGNAL_H
+  gl_SIGNBIT
+  if test $REPLACE_SIGNBIT = 1; then
+    AC_LIBOBJ([signbitf])
+    AC_LIBOBJ([signbitd])
+    AC_LIBOBJ([signbitl])
+  fi
+  gl_MATH_MODULE_INDICATOR([signbit])
   gl_SIZE_MAX
   gl_FUNC_SNPRINTF
   gl_STDIO_MODULE_INDICATOR([snprintf])
@@ -935,6 +967,7 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/close.c
   lib/config.charset
   lib/connect.c
+  lib/copysign.c
   lib/dirent.in.h
   lib/dirfd.c
   lib/dirname-lgpl.c
@@ -976,11 +1009,14 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/iconveh.h
   lib/inet_ntop.c
   lib/inet_pton.c
+  lib/isfinite.c
   lib/isinf.c
   lib/isnan.c
   lib/isnand-nolibm.h
   lib/isnand.c
+  lib/isnanf-nolibm.h
   lib/isnanf.c
+  lib/isnanl-nolibm.h
   lib/isnanl.c
   lib/itold.c
   lib/langinfo.in.h
@@ -1053,6 +1089,9 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/setsockopt.c
   lib/shutdown.c
   lib/signal.in.h
+  lib/signbitd.c
+  lib/signbitf.c
+  lib/signbitl.c
   lib/size_max.h
   lib/snprintf.c
   lib/socket.c
@@ -1125,6 +1164,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/close.m4
   m4/codeset.m4
   m4/configmake.m4
+  m4/copysign.m4
   m4/dirent_h.m4
   m4/dirfd.m4
   m4/dirname.m4
@@ -1163,6 +1203,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/inline.m4
   m4/intmax_t.m4
   m4/inttypes_h.m4
+  m4/isfinite.m4
   m4/isinf.m4
   m4/isnan.m4
   m4/isnand.m4
@@ -1228,6 +1269,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/servent.m4
   m4/setenv.m4
   m4/signal_h.m4
+  m4/signbit.m4
   m4/size_max.m4
   m4/snprintf.m4
   m4/socketlib.m4
diff --git a/m4/isfinite.m4 b/m4/isfinite.m4
new file mode 100644
index 000000000..b54b403b8
--- /dev/null
+++ b/m4/isfinite.m4
@@ -0,0 +1,165 @@
+# isfinite.m4 serial 13
+dnl Copyright (C) 2007-2013 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_ISFINITE],
+[
+  AC_REQUIRE([gl_MATH_H_DEFAULTS])
+  dnl Persuade glibc <math.h> to declare isfinite.
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+  AC_CHECK_DECLS([isfinite], , , [[#include <math.h>]])
+  if test "$ac_cv_have_decl_isfinite" = yes; then
+    gl_CHECK_MATH_LIB([ISFINITE_LIBM],
+     [x = isfinite (x) + isfinite ((float) x);])
+    if test "$ISFINITE_LIBM" != missing; then
+      dnl Test whether isfinite() on 'long double' works.
+      gl_ISFINITEL_WORKS
+      case "$gl_cv_func_isfinitel_works" in
+        *yes) ;;
+        *)    ISFINITE_LIBM=missing;;
+      esac
+      dnl Also, isfinite() on 'double' does not work on Linux/ia64 (because of
+      dnl signalling NaNs). But this does not have to be tested, since
+      dnl isfinite(long double) also does not work in this situation.
+    fi
+  fi
+  if test "$ac_cv_have_decl_isfinite" != yes ||
+     test "$ISFINITE_LIBM" = missing; then
+    REPLACE_ISFINITE=1
+    dnl No libraries are needed to link lib/isfinite.c.
+    ISFINITE_LIBM=
+  fi
+  AC_SUBST([ISFINITE_LIBM])
+])
+
+dnl Test whether isfinite() on 'long double' recognizes all numbers which are
+dnl neither finite nor infinite. This test fails e.g. on i686, x86_64, ia64,
+dnl because of
+dnl - pseudo-denormals on x86_64,
+dnl - pseudo-zeroes, unnormalized numbers, and pseudo-denormals on i686,
+dnl - pseudo-NaN, pseudo-Infinity, pseudo-zeroes, unnormalized numbers, and
+dnl   pseudo-denormals on ia64.
+AC_DEFUN([gl_ISFINITEL_WORKS],
+[
+  AC_REQUIRE([AC_PROG_CC])
+  AC_REQUIRE([gl_BIGENDIAN])
+  AC_REQUIRE([gl_LONG_DOUBLE_VS_DOUBLE])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  AC_CACHE_CHECK([whether isfinite(long double) works], [gl_cv_func_isfinitel_works],
+    [
+      AC_RUN_IFELSE([AC_LANG_SOURCE([[
+#include <float.h>
+#include <limits.h>
+#include <math.h>
+#define NWORDS \
+  ((sizeof (long double) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
+typedef union { unsigned int word[NWORDS]; long double value; }
+        memory_long_double;
+/* On Irix 6.5, gcc 3.4.3 can't compute compile-time NaN, and needs the
+   runtime type conversion.  */
+#ifdef __sgi
+static long double NaNl ()
+{
+  double zero = 0.0;
+  return zero / zero;
+}
+#else
+# define NaNl() (0.0L / 0.0L)
+#endif
+int main ()
+{
+  int result = 0;
+
+  {
+    memory_long_double m;
+    unsigned int i;
+
+    /* The isfinite macro should be immune against changes in the sign bit and
+       in the mantissa bits.  The xor operation twiddles a bit that can only be
+       a sign bit or a mantissa bit (since the exponent never extends to
+       bit 31).  */
+    m.value = NaNl ();
+    m.word[NWORDS / 2] ^= (unsigned int) 1 << (sizeof (unsigned int) * CHAR_BIT - 1);
+    for (i = 0; i < NWORDS; i++)
+      m.word[i] |= 1;
+    if (isfinite (m.value))
+      result |= 1;
+  }
+
+#if ((defined __ia64 && LDBL_MANT_DIG == 64) || (defined __x86_64__ || defined __amd64__) || (defined __i386 || defined __i386__ || defined _I386 || defined _M_IX86 || defined _X86_)) && !HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
+/* Representation of an 80-bit 'long double' as an initializer for a sequence
+   of 'unsigned int' words.  */
+# ifdef WORDS_BIGENDIAN
+#  define LDBL80_WORDS(exponent,manthi,mantlo) \
+     { ((unsigned int) (exponent) << 16) | ((unsigned int) (manthi) >> 16), \
+       ((unsigned int) (manthi) << 16) | (unsigned int) (mantlo) >> 16),    \
+       (unsigned int) (mantlo) << 16                                        \
+     }
+# else
+#  define LDBL80_WORDS(exponent,manthi,mantlo) \
+     { mantlo, manthi, exponent }
+# endif
+  { /* Quiet NaN.  */
+    static memory_long_double x =
+      { LDBL80_WORDS (0xFFFF, 0xC3333333, 0x00000000) };
+    if (isfinite (x.value))
+      result |= 2;
+  }
+  {
+    /* Signalling NaN.  */
+    static memory_long_double x =
+      { LDBL80_WORDS (0xFFFF, 0x83333333, 0x00000000) };
+    if (isfinite (x.value))
+      result |= 2;
+  }
+  /* The isfinite macro should recognize Pseudo-NaNs, Pseudo-Infinities,
+     Pseudo-Zeroes, Unnormalized Numbers, and Pseudo-Denormals, as defined in
+       Intel IA-64 Architecture Software Developer's Manual, Volume 1:
+       Application Architecture.
+       Table 5-2 "Floating-Point Register Encodings"
+       Figure 5-6 "Memory to Floating-Point Register Data Translation"
+   */
+  { /* Pseudo-NaN.  */
+    static memory_long_double x =
+      { LDBL80_WORDS (0xFFFF, 0x40000001, 0x00000000) };
+    if (isfinite (x.value))
+      result |= 4;
+  }
+  { /* Pseudo-Infinity.  */
+    static memory_long_double x =
+      { LDBL80_WORDS (0xFFFF, 0x00000000, 0x00000000) };
+    if (isfinite (x.value))
+      result |= 8;
+  }
+  { /* Pseudo-Zero.  */
+    static memory_long_double x =
+      { LDBL80_WORDS (0x4004, 0x00000000, 0x00000000) };
+    if (isfinite (x.value))
+      result |= 16;
+  }
+  { /* Unnormalized number.  */
+    static memory_long_double x =
+      { LDBL80_WORDS (0x4000, 0x63333333, 0x00000000) };
+    if (isfinite (x.value))
+      result |= 32;
+  }
+  { /* Pseudo-Denormal.  */
+    static memory_long_double x =
+      { LDBL80_WORDS (0x0000, 0x83333333, 0x00000000) };
+    if (isfinite (x.value))
+      result |= 64;
+  }
+#endif
+
+  return result;
+}]])], [gl_cv_func_isfinitel_works=yes], [gl_cv_func_isfinitel_works=no],
+      [case "$host_cpu" in
+                               # Guess no on ia64, x86_64, i386.
+         ia64 | x86_64 | i*86) gl_cv_func_isfinitel_works="guessing no";;
+         *)                    gl_cv_func_isfinitel_works="guessing yes";;
+       esac
+      ])
+    ])
+])
diff --git a/m4/signbit.m4 b/m4/signbit.m4
new file mode 100644
index 000000000..d58caaf05
--- /dev/null
+++ b/m4/signbit.m4
@@ -0,0 +1,365 @@
+# signbit.m4 serial 13
+dnl Copyright (C) 2007-2013 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_SIGNBIT],
+[
+  AC_REQUIRE([gl_MATH_H_DEFAULTS])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  AC_CACHE_CHECK([for signbit macro], [gl_cv_func_signbit],
+    [
+      AC_RUN_IFELSE(
+        [AC_LANG_SOURCE([[
+#include <math.h>
+/* If signbit is defined as a function, don't use it, since calling it for
+   'float' or 'long double' arguments would involve conversions.
+   If signbit is not declared at all but exists as a library function, don't
+   use it, since the prototype may not match.
+   If signbit is not declared at all but exists as a compiler built-in, don't
+   use it, since it's preferable to use __builtin_signbit* (no warnings,
+   no conversions).  */
+#ifndef signbit
+# error "signbit should be a macro"
+#endif
+#include <string.h>
+]gl_SIGNBIT_TEST_PROGRAM
+])],
+        [gl_cv_func_signbit=yes],
+        [gl_cv_func_signbit=no],
+        [case "$host_os" in
+                   # Guess yes on glibc systems.
+           *-gnu*) gl_cv_func_signbit="guessing yes" ;;
+                   # If we don't know, assume the worst.
+           *)      gl_cv_func_signbit="guessing no" ;;
+         esac
+        ])
+    ])
+  dnl GCC 4.0 and newer provides three built-ins for signbit.
+  dnl They can be used without warnings, also in C++, regardless of <math.h>.
+  dnl But they may expand to calls to functions, which may or may not be in
+  dnl libc.
+  AC_CACHE_CHECK([for signbit compiler built-ins], [gl_cv_func_signbit_gcc],
+    [
+      AC_RUN_IFELSE(
+        [AC_LANG_SOURCE([[
+#if __GNUC__ >= 4
+# define signbit(x) \
+   (sizeof (x) == sizeof (long double) ? __builtin_signbitl (x) : \
+    sizeof (x) == sizeof (double) ? __builtin_signbit (x) : \
+    __builtin_signbitf (x))
+#else
+# error "signbit should be three compiler built-ins"
+#endif
+#include <string.h>
+]gl_SIGNBIT_TEST_PROGRAM
+])],
+        [gl_cv_func_signbit_gcc=yes],
+        [gl_cv_func_signbit_gcc=no],
+        [case "$host_os" in
+                   # Guess yes on glibc systems.
+           *-gnu*) gl_cv_func_signbit_gcc="guessing yes" ;;
+                   # If we don't know, assume the worst.
+           *)      gl_cv_func_signbit_gcc="guessing no" ;;
+         esac
+        ])
+    ])
+  dnl Use the compiler built-ins whenever possible, because they are more
+  dnl efficient than the system library functions (if they exist).
+  case "$gl_cv_func_signbit_gcc" in
+    *yes)
+      REPLACE_SIGNBIT_USING_GCC=1
+      ;;
+    *)
+      case "$gl_cv_func_signbit" in
+        *yes) ;;
+        *)
+          dnl REPLACE_SIGNBIT=1 makes sure the signbit[fdl] functions get built.
+          REPLACE_SIGNBIT=1
+          gl_FLOAT_SIGN_LOCATION
+          gl_DOUBLE_SIGN_LOCATION
+          gl_LONG_DOUBLE_SIGN_LOCATION
+          if test "$gl_cv_cc_float_signbit" = unknown; then
+            dnl Test whether copysignf() is declared.
+            AC_CHECK_DECLS([copysignf], , , [[#include <math.h>]])
+            if test "$ac_cv_have_decl_copysignf" = yes; then
+              dnl Test whether copysignf() can be used without libm.
+              AC_CACHE_CHECK([whether copysignf can be used without linking with libm],
+                [gl_cv_func_copysignf_no_libm],
+                [
+                  AC_LINK_IFELSE(
+                    [AC_LANG_PROGRAM(
+                       [[#include <math.h>
+                         float x, y;]],
+                       [[return copysignf (x, y) < 0;]])],
+                    [gl_cv_func_copysignf_no_libm=yes],
+                    [gl_cv_func_copysignf_no_libm=no])
+                ])
+              if test $gl_cv_func_copysignf_no_libm = yes; then
+                AC_DEFINE([HAVE_COPYSIGNF_IN_LIBC], [1],
+                  [Define if the copysignf function is declared in <math.h> and available in libc.])
+              fi
+            fi
+          fi
+          if test "$gl_cv_cc_double_signbit" = unknown; then
+            dnl Test whether copysign() is declared.
+            AC_CHECK_DECLS([copysign], , , [[#include <math.h>]])
+            if test "$ac_cv_have_decl_copysign" = yes; then
+              dnl Test whether copysign() can be used without libm.
+              AC_CACHE_CHECK([whether copysign can be used without linking with libm],
+                [gl_cv_func_copysign_no_libm],
+                [
+                  AC_LINK_IFELSE(
+                    [AC_LANG_PROGRAM(
+                       [[#include <math.h>
+                         double x, y;]],
+                       [[return copysign (x, y) < 0;]])],
+                    [gl_cv_func_copysign_no_libm=yes],
+                    [gl_cv_func_copysign_no_libm=no])
+                ])
+              if test $gl_cv_func_copysign_no_libm = yes; then
+                AC_DEFINE([HAVE_COPYSIGN_IN_LIBC], [1],
+                  [Define if the copysign function is declared in <math.h> and available in libc.])
+              fi
+            fi
+          fi
+          if test "$gl_cv_cc_long_double_signbit" = unknown; then
+            dnl Test whether copysignl() is declared.
+            AC_CHECK_DECLS([copysignl], , , [[#include <math.h>]])
+            if test "$ac_cv_have_decl_copysignl" = yes; then
+              dnl Test whether copysignl() can be used without libm.
+              AC_CACHE_CHECK([whether copysignl can be used without linking with libm],
+                [gl_cv_func_copysignl_no_libm],
+                [
+                  AC_LINK_IFELSE(
+                    [AC_LANG_PROGRAM(
+                       [[#include <math.h>
+                         long double x, y;]],
+                       [[return copysignl (x, y) < 0;]])],
+                    [gl_cv_func_copysignl_no_libm=yes],
+                    [gl_cv_func_copysignl_no_libm=no])
+                ])
+              if test $gl_cv_func_copysignl_no_libm = yes; then
+                AC_DEFINE([HAVE_COPYSIGNL_IN_LIBC], [1],
+                  [Define if the copysignl function is declared in <math.h> and available in libc.])
+              fi
+            fi
+          fi
+          ;;
+      esac
+      ;;
+  esac
+])
+
+AC_DEFUN([gl_SIGNBIT_TEST_PROGRAM], [[
+/* Global variables.
+   Needed because GCC 4 constant-folds __builtin_signbitl (literal)
+   but cannot constant-fold            __builtin_signbitl (variable).  */
+float vf;
+double vd;
+long double vl;
+int main ()
+{
+/* HP cc on HP-UX 10.20 has a bug with the constant expression -0.0.
+   So we use -p0f and -p0d instead.  */
+float p0f = 0.0f;
+float m0f = -p0f;
+double p0d = 0.0;
+double m0d = -p0d;
+/* On HP-UX 10.20, negating 0.0L does not yield -0.0L.
+   So we use another constant expression instead.
+   But that expression does not work on other platforms, such as when
+   cross-compiling to PowerPC on Mac OS X 10.5.  */
+long double p0l = 0.0L;
+#if defined __hpux || defined __sgi
+long double m0l = -LDBL_MIN * LDBL_MIN;
+#else
+long double m0l = -p0l;
+#endif
+  int result = 0;
+  if (signbit (vf)) /* link check */
+    vf++;
+  {
+    float plus_inf = 1.0f / p0f;
+    float minus_inf = -1.0f / p0f;
+    if (!(!signbit (255.0f)
+          && signbit (-255.0f)
+          && !signbit (p0f)
+          && (memcmp (&m0f, &p0f, sizeof (float)) == 0 || signbit (m0f))
+          && !signbit (plus_inf)
+          && signbit (minus_inf)))
+      result |= 1;
+  }
+  if (signbit (vd)) /* link check */
+    vd++;
+  {
+    double plus_inf = 1.0 / p0d;
+    double minus_inf = -1.0 / p0d;
+    if (!(!signbit (255.0)
+          && signbit (-255.0)
+          && !signbit (p0d)
+          && (memcmp (&m0d, &p0d, sizeof (double)) == 0 || signbit (m0d))
+          && !signbit (plus_inf)
+          && signbit (minus_inf)))
+      result |= 2;
+  }
+  if (signbit (vl)) /* link check */
+    vl++;
+  {
+    long double plus_inf = 1.0L / p0l;
+    long double minus_inf = -1.0L / p0l;
+    if (signbit (255.0L))
+      result |= 4;
+    if (!signbit (-255.0L))
+      result |= 4;
+    if (signbit (p0l))
+      result |= 8;
+    if (!(memcmp (&m0l, &p0l, sizeof (long double)) == 0 || signbit (m0l)))
+      result |= 16;
+    if (signbit (plus_inf))
+      result |= 32;
+    if (!signbit (minus_inf))
+      result |= 64;
+  }
+  return result;
+}
+]])
+
+AC_DEFUN([gl_FLOAT_SIGN_LOCATION],
+[
+  gl_FLOATTYPE_SIGN_LOCATION([float], [gl_cv_cc_float_signbit], [f], [FLT])
+])
+
+AC_DEFUN([gl_DOUBLE_SIGN_LOCATION],
+[
+  gl_FLOATTYPE_SIGN_LOCATION([double], [gl_cv_cc_double_signbit], [], [DBL])
+])
+
+AC_DEFUN([gl_LONG_DOUBLE_SIGN_LOCATION],
+[
+  gl_FLOATTYPE_SIGN_LOCATION([long double], [gl_cv_cc_long_double_signbit], [L], [LDBL])
+])
+
+AC_DEFUN([gl_FLOATTYPE_SIGN_LOCATION],
+[
+  AC_CACHE_CHECK([where to find the sign bit in a '$1'],
+    [$2],
+    [
+      AC_RUN_IFELSE(
+        [AC_LANG_SOURCE([[
+#include <stddef.h>
+#include <stdio.h>
+#define NWORDS \
+  ((sizeof ($1) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
+typedef union { $1 value; unsigned int word[NWORDS]; }
+        memory_float;
+static memory_float plus = { 1.0$3 };
+static memory_float minus = { -1.0$3 };
+int main ()
+{
+  size_t j, k, i;
+  unsigned int m;
+  FILE *fp = fopen ("conftest.out", "w");
+  if (fp == NULL)
+    return 1;
+  /* Find the different bit.  */
+  k = 0; m = 0;
+  for (j = 0; j < NWORDS; j++)
+    {
+      unsigned int x = plus.word[j] ^ minus.word[j];
+      if ((x & (x - 1)) || (x && m))
+        {
+          /* More than one bit difference.  */
+          fprintf (fp, "unknown");
+          return 2;
+        }
+      if (x)
+        {
+          k = j;
+          m = x;
+        }
+    }
+  if (m == 0)
+    {
+      /* No difference.  */
+      fprintf (fp, "unknown");
+      return 3;
+    }
+  /* Now m = plus.word[k] ^ ~minus.word[k].  */
+  if (plus.word[k] & ~minus.word[k])
+    {
+      /* Oh? The sign bit is set in the positive and cleared in the negative
+         numbers?  */
+      fprintf (fp, "unknown");
+      return 4;
+    }
+  for (i = 0; ; i++)
+    if ((m >> i) & 1)
+      break;
+  fprintf (fp, "word %d bit %d", (int) k, (int) i);
+  if (fclose (fp) != 0)
+    return 5;
+  return 0;
+}
+        ]])],
+        [$2=`cat conftest.out`],
+        [$2="unknown"],
+        [
+          dnl When cross-compiling, we don't know. It depends on the
+          dnl ABI and compiler version. There are too many cases.
+          $2="unknown"
+        ])
+      rm -f conftest.out
+    ])
+  case "$]$2[" in
+    word*bit*)
+      word=`echo "$]$2[" | sed -e 's/word //' -e 's/ bit.*//'`
+      bit=`echo "$]$2[" | sed -e 's/word.*bit //'`
+      AC_DEFINE_UNQUOTED([$4][_SIGNBIT_WORD], [$word],
+        [Define as the word index where to find the sign of '$1'.])
+      AC_DEFINE_UNQUOTED([$4][_SIGNBIT_BIT], [$bit],
+        [Define as the bit index in the word where to find the sign of '$1'.])
+      ;;
+  esac
+])
+
+# Expands to code that defines a function signbitf(float).
+# It extracts the sign bit of a non-NaN value.
+AC_DEFUN([gl_FLOAT_SIGNBIT_CODE],
+[
+  gl_FLOATTYPE_SIGNBIT_CODE([float], [f], [f])
+])
+
+# Expands to code that defines a function signbitd(double).
+# It extracts the sign bit of a non-NaN value.
+AC_DEFUN([gl_DOUBLE_SIGNBIT_CODE],
+[
+  gl_FLOATTYPE_SIGNBIT_CODE([double], [d], [])
+])
+
+# Expands to code that defines a function signbitl(long double).
+# It extracts the sign bit of a non-NaN value.
+AC_DEFUN([gl_LONG_DOUBLE_SIGNBIT_CODE],
+[
+  gl_FLOATTYPE_SIGNBIT_CODE([long double], [l], [L])
+])
+
+AC_DEFUN([gl_FLOATTYPE_SIGNBIT_CODE],
+[[
+static int
+signbit$2 ($1 value)
+{
+  typedef union { $1 f; unsigned char b[sizeof ($1)]; } float_union;
+  static float_union plus_one = { 1.0$3 };   /* unused bits are zero here */
+  static float_union minus_one = { -1.0$3 }; /* unused bits are zero here */
+  /* Compute the sign bit mask as the XOR of plus_one and minus_one.  */
+  float_union u;
+  unsigned int i;
+  u.f = value;
+  for (i = 0; i < sizeof ($1); i++)
+    if (u.b[i] & (plus_one.b[i] ^ minus_one.b[i]))
+      return 1;
+  return 0;
+}
+]])