libstdc++-v3: add support for --enable-libstdcxx-time=c11

Add support for --enable-libstdcxx-time=c11 via the ISO C11
threads.h API function thrd_sleep().

Signed-off-by: Christopher Friedt <chris@friedt.co>

Author: cfriedt-friedtco

libstdc++-v3/acinclude.m4

@@ -1320,6 +1320,8 @@ dnl        not always desirable because, in glibc 2.16 and earlier, for
 dnl        example, in turn it triggers the linking of libpthread too,
 dnl        which activates locking,
 dnl        a large overhead for single-thread programs.
+dnl --enable-libstdcxx-time=c11
+dnl        checks for the availability of <threads.h> and thrd_sleep in libc.
 dnl --enable-libstdcxx-time=no
 dnl --disable-libstdcxx-time
 dnl        disables the checks completely
@@ -1333,7 +1335,7 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
 
   GLIBCXX_ENABLE(libstdcxx-time,auto,[[[=KIND]]],
     [use KIND for check type],
-    [permit yes|no|rt])
+    [permit yes|no|rt|c11])
 
   AC_LANG_SAVE
   AC_LANG_CPLUSPLUS
@@ -1345,6 +1347,9 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
   ac_has_clock_realtime=no
   ac_has_nanosleep=no
   ac_has_sched_yield=no
+  ac_has_thrd_sleep=no
+
+  AC_CHECK_HEADERS(threads.h, ac_has_threads_h=yes, ac_has_threads_h=no)
 
   if test x"$enable_libstdcxx_time" = x"auto"; then
 
@@ -1396,11 +1401,20 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
         ac_has_sched_yield=yes
     esac
 
+  elif test x"$enable_libstdcxx_time" = x"c11"; then
+    
+    # workaround for the error below until ac_cv_func_thrd_sleep is available when cross-compiling
+    # checking for library containing thrd_sleep...
+    # configure: error: Link tests are not allowed after GCC_NO_EXECUTABLES.
+    ac_has_thrd_sleep=yes
+
   elif test x"$enable_libstdcxx_time" != x"no"; then
 
     if test x"$enable_libstdcxx_time" = x"rt"; then
       AC_SEARCH_LIBS(clock_gettime, [rt])
       AC_SEARCH_LIBS(nanosleep, [rt])
+    elif test x"$enable_libstdcxx_time" = x"c11"; then
+      AC_CHECK_FUNC(thrd_sleep)
     else
       AC_CHECK_FUNC(clock_gettime)
       AC_CHECK_FUNC(nanosleep)
@@ -1537,6 +1551,9 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
   if test x"$ac_has_nanosleep" = x"yes"; then
     AC_DEFINE(_GLIBCXX_USE_NANOSLEEP, 1,
       [ Defined if nanosleep is available. ])
+  elif test x"$ac_has_thrd_sleep" = x"yes"; then
+    AC_DEFINE(_GLIBCXX_USE_THRD_SLEEP, 1,
+      [ Defined if thrd_sleep is available. ])
   else
       AC_MSG_CHECKING([for sleep])
       AC_TRY_COMPILE([#include <unistd.h>],
@@ -1557,7 +1574,7 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
       AC_MSG_RESULT($ac_has_usleep)
   fi
 
-  if test x"$ac_has_nanosleep$ac_has_sleep" = x"nono"; then
+  if test x"$ac_has_nanosleep$ac_has_sleep$ac_has_thrd_sleep" = x"nonono"; then
       ac_no_sleep=yes
       AC_MSG_CHECKING([for Sleep])
       AC_TRY_COMPILE([#include <windows.h>],

libstdc++-v3/configure

@@ -20493,7 +20493,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 if test "${enable_libstdcxx_time+set}" = set; then :
   enableval=$enable_libstdcxx_time;
       case "$enableval" in
-       yes|no|rt) ;;
+       yes|no|rt|c11) ;;
        *) as_fn_error $? "Unknown argument to enable/disable libstdcxx-time" "$LINENO" 5 ;;
 	  	        esac
 
@@ -20518,6 +20518,21 @@ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
   ac_has_clock_realtime=no
   ac_has_nanosleep=no
   ac_has_sched_yield=no
+  ac_has_thrd_sleep=no
+
+    for ac_header in threads.h
+do :
+  ac_fn_cxx_check_header_mongrel "$LINENO" "threads.h" "ac_cv_header_threads_h" "$ac_includes_default"
+if test "x$ac_cv_header_threads_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_THREADS_H 1
+_ACEOF
+  ac_has_threads_h=yes
+else
+  ac_has_threads_h=no
+fi
+
+done
 
   if test x"$enable_libstdcxx_time" = x"auto"; then
 
@@ -20627,6 +20642,13 @@ fi
         ac_has_sched_yield=yes
     esac
 
+  elif test x"$enable_libstdcxx_time" = x"c11"; then
+
+    # workaround for the error below until ac_cv_func_thrd_sleep is available when cross-compiling
+    # checking for library containing thrd_sleep...
+    # configure: error: Link tests are not allowed after GCC_NO_EXECUTABLES.
+    ac_has_thrd_sleep=yes
+
   elif test x"$enable_libstdcxx_time" != x"no"; then
 
     if test x"$enable_libstdcxx_time" = x"rt"; then
@@ -20748,6 +20770,11 @@ if test "$ac_res" != no; then :
 
 fi
 
+    elif test x"$enable_libstdcxx_time" = x"c11"; then
+      ac_fn_cxx_check_func "$LINENO" "thrd_sleep" "ac_cv_func_thrd_sleep"
+if test "x$ac_cv_func_thrd_sleep" = xyes; then :
+
+fi
     else
       ac_fn_cxx_check_func "$LINENO" "clock_gettime" "ac_cv_func_clock_gettime"
 if test "x$ac_cv_func_clock_gettime" = xyes; then :
@@ -21058,6 +21085,10 @@ $as_echo "#define _GLIBCXX_USE_SCHED_YIELD 1" >>confdefs.h
 
 $as_echo "#define _GLIBCXX_USE_NANOSLEEP 1" >>confdefs.h
 
+  elif test x"$ac_has_thrd_sleep" = x"yes"; then
+
+$as_echo "#define _GLIBCXX_USE_THRD_SLEEP 1" >>confdefs.h
+
   else
       { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sleep" >&5
 $as_echo_n "checking for sleep... " >&6; }
@@ -21114,7 +21145,7 @@ $as_echo "#define HAVE_USLEEP 1" >>confdefs.h
 $as_echo "$ac_has_usleep" >&6; }
   fi
 
-  if test x"$ac_has_nanosleep$ac_has_sleep" = x"nono"; then
+  if test x"$ac_has_nanosleep$ac_has_sleep$ac_has_thrd_sleep" = x"nonono"; then
       ac_no_sleep=yes
       { $as_echo "$as_me:${as_lineno-$LINENO}: checking for Sleep" >&5
 $as_echo_n "checking for Sleep... " >&6; }

libstdc++-v3/include/bits/this_thread_sleep.h

@@ -40,6 +40,10 @@
 # include <time.h>  // nanosleep
 #endif
 
+#ifdef _GLIBCXX_USE_THRD_SLEEP
+#include <threads.h>
+#endif
+
 namespace std _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
@@ -57,7 +61,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   {
 #ifndef _GLIBCXX_NO_SLEEP
 
-#ifndef _GLIBCXX_USE_NANOSLEEP
+#if !(defined(_GLIBCXX_USE_NANOSLEEP) || defined(_GLIBCXX_USE_THRD_SLEEP))
     void
     __sleep_for(chrono::seconds, chrono::nanoseconds);
 #endif
@@ -79,6 +83,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  };
 	while (::nanosleep(&__ts, &__ts) == -1 && errno == EINTR)
 	  { }
+#elif defined(_GLIBCXX_USE_THRD_SLEEP)
+	struct ::timespec __ts =
+	  {
+	    static_cast<std::time_t>(__s.count()),
+	    static_cast<long>(__ns.count())
+	  };
+  ::thrd_sleep(&__ts, &__ts);
 #else
 	__sleep_for(__s, __ns);
 #endif

libstdc++-v3/src/c++11/thread.cc

@@ -214,6 +214,13 @@ namespace this_thread
       };
     while (::nanosleep(&__ts, &__ts) == -1 && errno == EINTR)
       { }
+#elif defined(_GLIBCXX_HAVE_THRD_SLEEP)
+    struct ::timespec __ts =
+      {
+	static_cast<std::time_t>(__s.count()),
+	static_cast<long>(__ns.count())
+      };
+    ::thrd_sleep(&__ts, &__ts);
 #elif defined(_GLIBCXX_HAVE_SLEEP)
     const auto target = chrono::steady_clock::now() + __s + __ns;
     while (true)