--- a/libstdc++-v3/configure.ac	Thu Oct 25 07:37:49 2018 +0900
+++ b/libstdc++-v3/configure.ac	Thu Feb 13 11:34:05 2020 +0900
@@ -1,6 +1,5 @@
 # Process this file with autoreconf to produce a configure script.
 
-AC_PREREQ(2.64)
 AC_INIT(package-unused, version-unused,, libstdc++)
 AC_CONFIG_SRCDIR(src/shared/hashtable-aux.cc)
 AC_CONFIG_HEADER(config.h)
@@ -84,6 +83,8 @@
 AC_PROG_CXX
 CXXFLAGS="$save_CXXFLAGS"
 
+AC_SYS_LARGEFILE
+
 # Runs configure.host, and assorted other critical bits.  Sets
 # up critical shell variables.
 GLIBCXX_CONFIGURE
@@ -150,6 +151,7 @@
 GLIBCXX_ENABLE_PCH($is_hosted)
 GLIBCXX_ENABLE_THREADS
 GLIBCXX_ENABLE_ATOMIC_BUILTINS
+GLIBCXX_ENABLE_LOCK_POLICY
 GLIBCXX_ENABLE_DECIMAL_FLOAT
 GLIBCXX_ENABLE_INT128_FLOAT128
 if test "$enable_float128" = yes; then
@@ -220,6 +222,15 @@
 # Check for tmpnam which is obsolescent in POSIX.1-2008
 GLIBCXX_CHECK_TMPNAM
 
+# For pthread_cond_clockwait
+GLIBCXX_CHECK_PTHREAD_COND_CLOCKWAIT
+
+# For pthread_mutex_clocklock
+GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK
+
+# For pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock
+GLIBCXX_CHECK_PTHREAD_RWLOCK_CLOCKLOCK
+
 AC_LC_MESSAGES
 
 # For hardware_concurrency
@@ -265,6 +276,12 @@
   AC_CHECK_FUNCS(aligned_alloc posix_memalign memalign _aligned_malloc)
   AC_CHECK_FUNCS(_wfopen)
 
+  # C11 functions for C++17 library
+  AC_CHECK_FUNCS(timespec_get)
+
+  # For Networking TS.
+  AC_CHECK_FUNCS(sockatmark)
+
   # For iconv support.
   AM_ICONV
 
@@ -411,6 +428,8 @@
 
 # Check if assembler supports rdrand opcode.
 GLIBCXX_CHECK_X86_RDRAND
+# Check if assembler supports rdseed opcode.
+GLIBCXX_CHECK_X86_RDSEED
 
 # This depends on GLIBCXX_ENABLE_SYMVERS and GLIBCXX_IS_NATIVE.
 GLIBCXX_CONFIGURE_TESTSUITE
@@ -446,6 +465,7 @@
 AC_CHECK_PROG([DOT], dot, yes, no)
 
 # Check for docbook
+AC_CHECK_PROG([XMLCATALOG], xmlcatalog, yes, no)
 AC_CHECK_PROG([XSLTPROC], xsltproc, yes, no)
 AC_CHECK_PROG([XMLLINT], xmllint, yes, no)
 GLIBCXX_CONFIGURE_DOCBOOK
@@ -474,6 +494,10 @@
 AC_CHECK_PROG([DBLATEX], dblatex, yes, no)
 AC_CHECK_PROG([PDFLATEX], pdflatex, yes, no)
 AM_CONDITIONAL(BUILD_PDF,
+	       test $ac_cv_prog_DOXYGEN = "yes" &&
+	       test $ac_cv_prog_DOT = "yes" &&
+	       test $ac_cv_prog_XSLTPROC = "yes" &&
+	       test $ac_cv_prog_XMLLINT = "yes" &&
 	       test $ac_cv_prog_DBLATEX = "yes" &&
 	       test $ac_cv_prog_PDFLATEX = "yes")