diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 663312da1e3..947bfd2d921 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,10 @@
+2019-12-25  Alexandre Oliva <oliva@adacore.com>
+
+	* crossconfig.m4 (GLIBCXX_CROSSCONFIG) [*-vxworks*]: Define
+	long double functions as available if declared by math.h.
+	(GLIBCXX_CHECK_MATH_DECL, GLIBCXX_CHECK_MATH_DECLS): New.
+	* configure: Rebuild.
+
 2019-12-20  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/92927
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index f2d52fd05f3..d96bd1457ec 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -72927,6 +72927,1110 @@ done
 
     $as_echo "#define HAVE_TANHF 1" >>confdefs.h
 
+
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for acosl declaration" >&5
+$as_echo_n "checking for acosl declaration... " >&6; }
+if ${glibcxx_cv_func_acosl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))acosl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_acosl_use=yes
+
+else
+  glibcxx_cv_func_acosl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_acosl_use" >&5
+$as_echo "$glibcxx_cv_func_acosl_use" >&6; }
+  if test "x$glibcxx_cv_func_acosl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_ACOSL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for asinl declaration" >&5
+$as_echo_n "checking for asinl declaration... " >&6; }
+if ${glibcxx_cv_func_asinl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))asinl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_asinl_use=yes
+
+else
+  glibcxx_cv_func_asinl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_asinl_use" >&5
+$as_echo "$glibcxx_cv_func_asinl_use" >&6; }
+  if test "x$glibcxx_cv_func_asinl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_ASINL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for atan2l declaration" >&5
+$as_echo_n "checking for atan2l declaration... " >&6; }
+if ${glibcxx_cv_func_atan2l_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))atan2l;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_atan2l_use=yes
+
+else
+  glibcxx_cv_func_atan2l_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_atan2l_use" >&5
+$as_echo "$glibcxx_cv_func_atan2l_use" >&6; }
+  if test "x$glibcxx_cv_func_atan2l_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_ATAN2L 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for atanl declaration" >&5
+$as_echo_n "checking for atanl declaration... " >&6; }
+if ${glibcxx_cv_func_atanl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))atanl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_atanl_use=yes
+
+else
+  glibcxx_cv_func_atanl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_atanl_use" >&5
+$as_echo "$glibcxx_cv_func_atanl_use" >&6; }
+  if test "x$glibcxx_cv_func_atanl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_ATANL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ceill declaration" >&5
+$as_echo_n "checking for ceill declaration... " >&6; }
+if ${glibcxx_cv_func_ceill_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))ceill;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_ceill_use=yes
+
+else
+  glibcxx_cv_func_ceill_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_ceill_use" >&5
+$as_echo "$glibcxx_cv_func_ceill_use" >&6; }
+  if test "x$glibcxx_cv_func_ceill_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_CEILL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for cosl declaration" >&5
+$as_echo_n "checking for cosl declaration... " >&6; }
+if ${glibcxx_cv_func_cosl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))cosl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_cosl_use=yes
+
+else
+  glibcxx_cv_func_cosl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_cosl_use" >&5
+$as_echo "$glibcxx_cv_func_cosl_use" >&6; }
+  if test "x$glibcxx_cv_func_cosl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_COSL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for coshl declaration" >&5
+$as_echo_n "checking for coshl declaration... " >&6; }
+if ${glibcxx_cv_func_coshl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))coshl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_coshl_use=yes
+
+else
+  glibcxx_cv_func_coshl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_coshl_use" >&5
+$as_echo "$glibcxx_cv_func_coshl_use" >&6; }
+  if test "x$glibcxx_cv_func_coshl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_COSHL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for expl declaration" >&5
+$as_echo_n "checking for expl declaration... " >&6; }
+if ${glibcxx_cv_func_expl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))expl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_expl_use=yes
+
+else
+  glibcxx_cv_func_expl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_expl_use" >&5
+$as_echo "$glibcxx_cv_func_expl_use" >&6; }
+  if test "x$glibcxx_cv_func_expl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_EXPL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for fabsl declaration" >&5
+$as_echo_n "checking for fabsl declaration... " >&6; }
+if ${glibcxx_cv_func_fabsl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))fabsl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_fabsl_use=yes
+
+else
+  glibcxx_cv_func_fabsl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_fabsl_use" >&5
+$as_echo "$glibcxx_cv_func_fabsl_use" >&6; }
+  if test "x$glibcxx_cv_func_fabsl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_FABSL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for floorl declaration" >&5
+$as_echo_n "checking for floorl declaration... " >&6; }
+if ${glibcxx_cv_func_floorl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))floorl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_floorl_use=yes
+
+else
+  glibcxx_cv_func_floorl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_floorl_use" >&5
+$as_echo "$glibcxx_cv_func_floorl_use" >&6; }
+  if test "x$glibcxx_cv_func_floorl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_FLOORL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for fmodl declaration" >&5
+$as_echo_n "checking for fmodl declaration... " >&6; }
+if ${glibcxx_cv_func_fmodl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))fmodl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_fmodl_use=yes
+
+else
+  glibcxx_cv_func_fmodl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_fmodl_use" >&5
+$as_echo "$glibcxx_cv_func_fmodl_use" >&6; }
+  if test "x$glibcxx_cv_func_fmodl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_FMODL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for frexpl declaration" >&5
+$as_echo_n "checking for frexpl declaration... " >&6; }
+if ${glibcxx_cv_func_frexpl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))frexpl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_frexpl_use=yes
+
+else
+  glibcxx_cv_func_frexpl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_frexpl_use" >&5
+$as_echo "$glibcxx_cv_func_frexpl_use" >&6; }
+  if test "x$glibcxx_cv_func_frexpl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_FREXPL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ldexpl declaration" >&5
+$as_echo_n "checking for ldexpl declaration... " >&6; }
+if ${glibcxx_cv_func_ldexpl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))ldexpl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_ldexpl_use=yes
+
+else
+  glibcxx_cv_func_ldexpl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_ldexpl_use" >&5
+$as_echo "$glibcxx_cv_func_ldexpl_use" >&6; }
+  if test "x$glibcxx_cv_func_ldexpl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_LDEXPL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for log10l declaration" >&5
+$as_echo_n "checking for log10l declaration... " >&6; }
+if ${glibcxx_cv_func_log10l_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))log10l;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_log10l_use=yes
+
+else
+  glibcxx_cv_func_log10l_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_log10l_use" >&5
+$as_echo "$glibcxx_cv_func_log10l_use" >&6; }
+  if test "x$glibcxx_cv_func_log10l_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_LOG10L 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for logl declaration" >&5
+$as_echo_n "checking for logl declaration... " >&6; }
+if ${glibcxx_cv_func_logl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))logl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_logl_use=yes
+
+else
+  glibcxx_cv_func_logl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_logl_use" >&5
+$as_echo "$glibcxx_cv_func_logl_use" >&6; }
+  if test "x$glibcxx_cv_func_logl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_LOGL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for modfl declaration" >&5
+$as_echo_n "checking for modfl declaration... " >&6; }
+if ${glibcxx_cv_func_modfl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))modfl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_modfl_use=yes
+
+else
+  glibcxx_cv_func_modfl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_modfl_use" >&5
+$as_echo "$glibcxx_cv_func_modfl_use" >&6; }
+  if test "x$glibcxx_cv_func_modfl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_MODFL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for powl declaration" >&5
+$as_echo_n "checking for powl declaration... " >&6; }
+if ${glibcxx_cv_func_powl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))powl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_powl_use=yes
+
+else
+  glibcxx_cv_func_powl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_powl_use" >&5
+$as_echo "$glibcxx_cv_func_powl_use" >&6; }
+  if test "x$glibcxx_cv_func_powl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_POWL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sinl declaration" >&5
+$as_echo_n "checking for sinl declaration... " >&6; }
+if ${glibcxx_cv_func_sinl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))sinl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_sinl_use=yes
+
+else
+  glibcxx_cv_func_sinl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_sinl_use" >&5
+$as_echo "$glibcxx_cv_func_sinl_use" >&6; }
+  if test "x$glibcxx_cv_func_sinl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_SINL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sinhl declaration" >&5
+$as_echo_n "checking for sinhl declaration... " >&6; }
+if ${glibcxx_cv_func_sinhl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))sinhl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_sinhl_use=yes
+
+else
+  glibcxx_cv_func_sinhl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_sinhl_use" >&5
+$as_echo "$glibcxx_cv_func_sinhl_use" >&6; }
+  if test "x$glibcxx_cv_func_sinhl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_SINHL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sqrtl declaration" >&5
+$as_echo_n "checking for sqrtl declaration... " >&6; }
+if ${glibcxx_cv_func_sqrtl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))sqrtl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_sqrtl_use=yes
+
+else
+  glibcxx_cv_func_sqrtl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_sqrtl_use" >&5
+$as_echo "$glibcxx_cv_func_sqrtl_use" >&6; }
+  if test "x$glibcxx_cv_func_sqrtl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_SQRTL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for tanl declaration" >&5
+$as_echo_n "checking for tanl declaration... " >&6; }
+if ${glibcxx_cv_func_tanl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))tanl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_tanl_use=yes
+
+else
+  glibcxx_cv_func_tanl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_tanl_use" >&5
+$as_echo "$glibcxx_cv_func_tanl_use" >&6; }
+  if test "x$glibcxx_cv_func_tanl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_TANL 1
+_ACEOF
+
+  fi
+
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for tanhl declaration" >&5
+$as_echo_n "checking for tanhl declaration... " >&6; }
+if ${glibcxx_cv_func_tanhl_use+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+
+      ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+
+int
+main ()
+{
+
+  void (*f)(void) = (void (*)(void))tanhl;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  glibcxx_cv_func_tanhl_use=yes
+
+else
+  glibcxx_cv_func_tanhl_use=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_func_tanhl_use" >&5
+$as_echo "$glibcxx_cv_func_tanhl_use" >&6; }
+  if test "x$glibcxx_cv_func_tanhl_use" = xyes; then
+    cat >>confdefs.h <<_ACEOF
+#define HAVE_TANHL 1
+_ACEOF
+
+  fi
+
+
+
     ;;
   *)
     as_fn_error $? "No support for this host/target combination." "$LINENO" 5
diff --git a/libstdc++-v3/crossconfig.m4 b/libstdc++-v3/crossconfig.m4
index 5e248897943..2a0cb0475e5 100644
--- a/libstdc++-v3/crossconfig.m4
+++ b/libstdc++-v3/crossconfig.m4
@@ -291,9 +291,71 @@ case "${host}" in
     AC_DEFINE(HAVE_SQRTF)
     AC_DEFINE(HAVE_TANF)
     AC_DEFINE(HAVE_TANHF)
+
+dnl # Different versions and execution modes implement different
+dnl # subsets of these functions.  Instead of hard-coding, test for C
+dnl # declarations in headers.  The C primitives could be defined as
+dnl # macros, in which case the tests might fail, and we might have to
+dnl # switch to more elaborate tests.
+    GLIBCXX_CHECK_MATH_DECLS([
+      acosl asinl atan2l atanl ceill cosl coshl expl fabsl floorl fmodl
+      frexpl ldexpl log10l logl modfl powl sinl sinhl sqrtl tanl tanhl])
+dnl # sincosl is the only one missing here, compared with the *l
+dnl # functions in the list guarded by
+dnl # long_double_math_on_this_cpu in configure.ac, right after
+dnl # the expansion of the present macro.
     ;;
   *)
     AC_MSG_ERROR([No support for this host/target combination.])
    ;;
 esac
 ])
+
+
+dnl
+dnl Check to see if the (math function) argument passed is
+dnl declared when using the c compiler
+dnl
+dnl Define HAVE_CARGF etc if "cargf" is declared
+dnl
+dnl argument 1 is name of function to check
+dnl
+dnl ASSUMES argument is a math function
+dnl
+dnl GLIBCXX_CHECK_MATH_DECL
+AC_DEFUN([GLIBCXX_CHECK_MATH_DECL], [
+  AC_CACHE_CHECK([for $1 declaration],
+    [glibcxx_cv_func_$1_use], [
+      AC_LANG_SAVE
+      AC_LANG_C
+      AC_TRY_COMPILE([
+#include <math.h>
+#ifdef HAVE_IEEEFP_H
+# include <ieeefp.h>
+#endif
+], [
+  void (*f)(void) = (void (*)(void))$1;
+], [glibcxx_cv_func_$1_use=yes
+], [glibcxx_cv_func_$1_use=no])])
+  if test "x$glibcxx_cv_func_$1_use" = xyes; then
+    AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE_$1]))
+  fi
+])
+
+dnl
+dnl Check to see whether multiple math functions are
+dnl declared when using the c compiler
+dnl
+dnl Define HAVE_CARGF HAVE_POWL etc if "cargf" and "powl"
+dnl are declared
+dnl
+dnl argument 1 is a word list naming function to check
+dnl
+dnl ASSUMES arguments are math functions
+dnl
+dnl GLIBCXX_CHECK_MATH_DECLS
+AC_DEFUN([GLIBCXX_CHECK_MATH_DECLS], [
+  m4_foreach_w([glibcxx_func], [$1], [
+    GLIBCXX_CHECK_MATH_DECL(glibcxx_func)
+  ])
+])