This alters the configure script to enable C++11 thread library
features based on targets that are known to support the features,
rather than based on link tests which are disabled by default. With
Glibc 2.17 this enables a nanosecond resolution std::system_clock in
the default configuration, yay!
I've tested this on two versions of Fedora and Debian, but would be
grateful for test results on Solaris, Cygwin and BSD targets, and for
cross-compilers to any of those targets.
* acinclude.m4 (GLIBCXX_ENABLE_LIBSTDCXX_TIME): Add KIND=auto to
enable features if target OS is known to support them.
* configure.ac (GLIBCXX_ENABLE_LIBSTDCXX_TIME): Default to 'auto'.
* configure: Regenerate.
Tested x86_64-linux, committed to trunk.
commit 47e011c33d78a00015265be39f2845209eeb97fc
Author: Jonathan Wakely <jwakely....@gmail.com>
Date: Sun Feb 3 20:45:51 2013 +0000
* acinclude.m4 (GLIBCXX_ENABLE_LIBSTDCXX_TIME): Add KIND=auto to
enable features if target OS is known to support them.
* configure.ac (GLIBCXX_ENABLE_LIBSTDCXX_TIME): Default to 'auto'.
* configure: Regenerate.
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 619fff0..efeb6d4 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -871,7 +871,8 @@ dnl (FEATURE, DEFAULT, HELP-ARG, HELP-STRING)
dnl (FEATURE, DEFAULT, HELP-ARG, HELP-STRING, permit a|b|c)
dnl (FEATURE, DEFAULT, HELP-ARG, HELP-STRING, SHELL-CODE-HANDLER)
dnl
-dnl See docs/html/17_intro/configury.html#enable for documentation.
+dnl See manual/appendix_porting.html#appendix.porting.build_hacking for
+dnl documentation.
dnl
m4_define([GLIBCXX_ENABLE],[dnl
m4_define([_g_switch],[--enable-$1])dnl
@@ -1161,8 +1162,9 @@ dnl nanosleep and sched_yield in libc and
libposix4 and, if needed,
dnl links in the latter.
dnl --enable-libstdcxx-time=rt
dnl also searches (and, if needed, links) librt. Note that this is
-dnl not always desirable because, in glibc, for example, in turn it
-dnl triggers the linking of libpthread too, which activates locking,
+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=no
dnl --disable-libstdcxx-time
@@ -1175,8 +1177,7 @@ dnl os_defines.h and also defines
_GLIBCXX_USE_SCHED_YIELD.
dnl
AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
- AC_MSG_CHECKING([for clock_gettime, nanosleep and sched_yield])
- GLIBCXX_ENABLE(libstdcxx-time,$1,[[[=KIND]]],
+ GLIBCXX_ENABLE(libstdcxx-time,auto,[[[=KIND]]],
[use KIND for check type],
[permit yes|no|rt])
@@ -1188,9 +1189,59 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
ac_has_clock_monotonic=no
ac_has_clock_realtime=no
- AC_MSG_RESULT($enable_libstdcxx_time)
+ ac_has_nanosleep=no
+ ac_has_sched_yield=no
+
+ if test x"$enable_libstdcxx_time" = x"auto"; then
+
+ case "${target_os}" in
+ cygwin*)
+ ac_has_nanosleep=yes
+ ;;
+ darwin*)
+ ac_has_nanosleep=yes
+ ac_has_sched_yield=yes
+ ;;
+ gnu* | linux* | kfreebsd*-gnu | knetbsd*-gnu)
+ AC_MSG_CHECKING([for at least GNU libc 2.17])
+ AC_TRY_COMPILE(
+ [#include <features.h>],
+ [
+ #if ! __GLIBC_PREREQ(2, 17)
+ #error
+ #endif
+ ],
+ [glibcxx_glibc217=yes], [glibcxx_glibc217=no])
+ AC_MSG_RESULT($glibcxx_glibc217)
+
+ if test x"$glibcxx_glibc217" = x"yes"; then
+ ac_has_clock_monotonic=yes
+ ac_has_clock_realtime=yes
+ fi
+ ac_has_nanosleep=yes
+ ac_has_sched_yield=yes
+ ;;
+ freebsd*|netbsd*)
+ ac_has_clock_monotonic=yes
+ ac_has_clock_realtime=yes
+ ac_has_nanosleep=yes
+ ac_has_sched_yield=yes
+ ;;
+ openbsd*)
+ ac_has_clock_monotonic=yes
+ ac_has_clock_realtime=yes
+ ac_has_nanosleep=yes
+ ;;
+ solaris*)
+ GLIBCXX_LIBS="$GLIBCXX_LIBS -lrt"
+ ac_has_clock_monotonic=yes
+ ac_has_clock_realtime=yes
+ ac_has_nanosleep=yes
+ ac_has_sched_yield=yes
+ ;;
+ esac
- if test x"$enable_libstdcxx_time" != x"no"; then
+ elif test x"$enable_libstdcxx_time" != x"no"; then
if test x"$enable_libstdcxx_time" = x"rt"; then
AC_SEARCH_LIBS(clock_gettime, [rt posix4])
@@ -1214,19 +1265,16 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
case "$ac_cv_search_sched_yield" in
-lposix4*)
GLIBCXX_LIBS="$GLIBCXX_LIBS $ac_cv_search_sched_yield"
- AC_DEFINE(_GLIBCXX_USE_SCHED_YIELD, 1,
- [ Defined if sched_yield is available. ])
+ ac_has_sched_yield=yes
;;
-lrt*)
if test x"$enable_libstdcxx_time" = x"rt"; then
GLIBCXX_LIBS="$GLIBCXX_LIBS $ac_cv_search_sched_yield"
- AC_DEFINE(_GLIBCXX_USE_SCHED_YIELD, 1,
- [ Defined if sched_yield is available. ])
+ ac_has_sched_yield=yes
fi
;;
*)
- AC_DEFINE(_GLIBCXX_USE_SCHED_YIELD, 1,
- [ Defined if sched_yield is available. ])
+ ac_has_sched_yield=yes
;;
esac
@@ -1284,6 +1332,11 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
[ Defined if clock_gettime has realtime clock support. ])
fi
+ if test x"$ac_has_sched_yield" = x"yes"; then
+ AC_DEFINE(_GLIBCXX_USE_SCHED_YIELD, 1,
+ [ Defined if sched_yield is available. ])
+ fi
+
if test x"$ac_has_nanosleep" = x"yes"; then
AC_DEFINE(_GLIBCXX_USE_NANOSLEEP, 1,
[ Defined if nanosleep is available. ])
diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
index 73d430a..f6ba176 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -198,8 +198,7 @@ GLIBCXX_COMPUTE_STDIO_INTEGER_CONSTANTS
GLIBCXX_CHECK_GETTIMEOFDAY
# For clock_gettime, nanosleep and sched_yield support.
-# NB: The default is [no], because otherwise it requires linking.
-GLIBCXX_ENABLE_LIBSTDCXX_TIME([no])
+GLIBCXX_ENABLE_LIBSTDCXX_TIME
AC_LC_MESSAGES
