[PATCH] Add std::timespec and std::timespec_get for C++17

[Jonathan Wakely]

        * configure.ac: Check for C11 timespec_get function.
        * crossconfig.m4 (freebsd, linux, gnu, cygwin, solaris, netbsd)
        (openbsd): Likewise
        * config.h.in: Regenerate.
        * configure: Regenerate.
        * include/c_global/ctime (timespec, timespec_get): Add to namespace
        std for C++17 and up.

Tested powerpc64le-linux (and bootstrapped on aarch64-linux-gnu cross
compiler), committed to trunk.



commit 9c433c582ce9ca7a12a61a1e674ca7b3885318d8
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Thu Feb 14 11:06:46 2019 +0000

    Add std::timespec and std::timespec_get for C++17
    
            * configure.ac: Check for C11 timespec_get function.
            * crossconfig.m4 (freebsd, linux, gnu, cygwin, solaris, netbsd)
            (openbsd): Likewise
            * config.h.in: Regenerate.
            * configure: Regenerate.
            * include/c_global/ctime (timespec, timespec_get): Add to namespace
            std for C++17 and up.

diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
index ad5b4117cfd..6c98f270441 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -265,6 +265,9 @@ if $GLIBCXX_IS_NATIVE; then
   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 iconv support.
   AM_ICONV
 
diff --git a/libstdc++-v3/crossconfig.m4 b/libstdc++-v3/crossconfig.m4
index 3de40dc138b..4a303008053 100644
--- a/libstdc++-v3/crossconfig.m4
+++ b/libstdc++-v3/crossconfig.m4
@@ -135,6 +135,7 @@ case "${host}" in
     fi
     AC_CHECK_FUNCS(__cxa_thread_atexit)
     AC_CHECK_FUNCS(aligned_alloc posix_memalign memalign _aligned_malloc)
+    AC_CHECK_FUNCS(timespec_get)
     ;;
 
   *-fuchsia*)
@@ -194,6 +195,7 @@ case "${host}" in
     GCC_CHECK_TLS
     AC_CHECK_FUNCS(__cxa_thread_atexit_impl)
     AC_CHECK_FUNCS(aligned_alloc posix_memalign memalign _aligned_malloc)
+    AC_CHECK_FUNCS(timespec_get)
     AM_ICONV
     ;;
   *-mingw32*)
@@ -221,6 +223,7 @@ case "${host}" in
       AC_DEFINE(HAVE_ISNANL)
     fi
     AC_CHECK_FUNCS(aligned_alloc posix_memalign memalign _aligned_malloc)
+    AC_CHECK_FUNCS(timespec_get)
     ;;
   *-qnx6.1* | *-qnx6.2*)
     SECTION_FLAGS='-ffunction-sections -fdata-sections'
diff --git a/libstdc++-v3/include/c_global/ctime 
b/libstdc++-v3/include/c_global/ctime
index cdd3d8d7171..685c821b577 100644
--- a/libstdc++-v3/include/c_global/ctime
+++ b/libstdc++-v3/include/c_global/ctime
@@ -72,4 +72,13 @@ namespace std
   using ::strftime;
 } // namespace
 
+#if __cplusplus >= 201703L && defined(_GLIBCXX_HAVE_TIMESPEC_GET)
+#undef timespec_get
+namespace std
+{
+  using ::timespec;
+  using ::timespec_get;
+} // namespace std
+#endif
+
 #endif