Patchwork Default to --enable-libstdcxx-time=auto

login
register
mail settings
Submitter Benjamin Kosnik
Date May 25, 2013, 6:56 p.m.
Message ID <20130525115631.210589ea@oakwood>
Download mbox | patch
Permalink /patch/246352/
State New
Headers show

Comments

Benjamin Kosnik - May 25, 2013, 6:56 p.m.
> > It scraps the renaming/aliasing approach, and just creates a
> > compatibility-chrono.cc that mimics the default configuration in
> > 4.8.0.
> 
> Yeah, I think that is reasonable, with one nit, see below.

Cool, incorporated.
 
> > Users who specially-configured a build with --enable-libstdcxx-time
> > configure options in 4.8.0 are breaking an experimental
> > C++ ABI anyway, so I'm not going to solve for anything but the
> > default case.
> > 
> > For chrono.cc, there is an inline namespace that mangles
> > system_clock and steady_clock in a new way to prevent ambiguous
> > uses. In addition, I make a controversial decision and just
> > forward-declare clocks that libstdc++ cannot do correctly, instead
> > of using typedefs that clearly are only going to get us into
> > trouble as we change things down the road. That's probably only
> > appropriate for trunk.
> 
> > +    // To support the (forward) evolving definition of the
> > library's
> > +    // defined clocks, wrap inside inline namespace so that these
> > +    // types are uniquely mangled. This way, new code can use the
> > +    // current clocks, while the library can contain old
> > definitions.
> > +    // At some point, when these clocks settle down, the inlined
> > +    // namespaces can be removed.
> > +    // XXX GLIBCXX_ABI Deprecated
> > +    inline namespace _V2 {
> > +
> >      /// system_clock
> >      struct system_clock
> >      {
> 
> In this _V2 inline namespace, I think we should change that:
>     struct system_clock
>     {
> #ifdef _GLIBCXX_USE_CLOCK_REALTIME
>       typedef chrono::nanoseconds
> duration; #elif defined(_GLIBCXX_USE_GETTIMEOFDAY)
>       typedef chrono::microseconds
> duration; #else
>       typedef chrono::seconds
> duration; #endif
> into:
>     struct system_clock
>     {
>       typedef chrono::nanoseconds
> duration;
> 
> Won't the templates then DTRT in:
>   return time_point(duration(chrono::seconds(tv.tv_sec)
> 		    + chrono::microseconds(tv.tv_usec)));
> (multiply microseconds by 1000 and seconds by 1000000000)
>       return system_clock::from_time_t(__sec);
> (multiply seconds by 1000000000)?

Yes.
 
> While this change isn't really necessary for Linux, where usually
> _GLIBCXX_USE_CLOCK_REALTIME will be in 4.8.1+ defined and thus the
> nanoseconds resolution will be used anyway, on other OSes it might
> be already a problem, say on Solaris or FreeBSD GCC 4.8.1 will have
> by default likely microseconds resolution, while on the trunk
> nanoseconds. By making it always count in nanoseconds, even if on
> some OSes the low 3 or 9 decimal digits will be always zero, we'd
> prepared to change the system_clock::now() implementation any time to
> provide better resolution, as a libstdc++ internal implementation
> detail.
> 
> Or is this undesirable for users for some reason?

I think your rationale is sound here. I've added some of these comments
to the code.

> 
> > @@ -742,10 +751,18 @@ _GLIBCXX_END_NAMESPACE_VERSION
> >        now() noexcept;
> >      };
> >  #else
> > -    typedef system_clock steady_clock;
> > +    // Forward declare only.
> > +    struct steady_clock;
> >  #endif
> >  
> > +#ifdef _GLIBCXX_USE_CLOCK_REALTIME
> >      typedef system_clock high_resolution_clock;
> > +#else
> > +    // Forward declare only.
> > +    struct high_resolution_clock;
> > +#endif
> > +
> > +  } // end inline namespace _V2
> 
> Yeah, I bet this hunk should be left out from 4.8.1 version of the
> patch.

I did something different, anyway.

Un-guardedly declare the clocks, and then just use the definitions in
the .cc file to define QoI. That way there is a symbol exported in all
configs, but one that can be improve in the future w/o pain. 

> Perhaps we also want some testcase that will roughly test it, like
> grab time(NULL), std::chrono::system_clock::now() and
> std::chrono::steady_clock::now(), then sleep(3), grab both clocks
> again and time(NULL) last, then if the difference between time() is
> at least 2 seconds and less than say 10, verify the difference
> between the clocks is say in a 1 to 20 seconds interval (yeah, it
> could fail badly if one changes system time in between once or
> several times)?  But maybe it would be too flakey.

Agreed, certainly room for improvement. Let's separate out this part
though.

I'm tempted to check this patch into trunk. Jakub?

tested x86_64/linux

-benjamin
Jakub Jelinek - May 25, 2013, 7:19 p.m.
On Sat, May 25, 2013 at 11:56:31AM -0700, Benjamin De Kosnik wrote:
> I'm tempted to check this patch into trunk. Jakub?

Looks good to me.  Will you prepare corresponding patch for the 4.8 branch
too (I guess it should be pretty much the same, not sure if it should keep
using typedef system_clock steady_clock as before for the non-MONOTONIC
configuration, or if it should just do the same thing as trunk)?

Thanks.

	Jakub
Benjamin Kosnik - May 25, 2013, 11:07 p.m.
> Looks good to me.  

Great, trunk patch in.

> Will you prepare corresponding patch for the 4.8
> branch too (I guess it should be pretty much the same, not sure if it
> should keep using typedef system_clock steady_clock as before for the
> non-MONOTONIC configuration, or if it should just do the same thing
> as trunk)?

Same thing, I think. Testing now, ok when it completes?

-benjamin
Jakub Jelinek - May 26, 2013, 5:58 a.m.
On Sat, May 25, 2013 at 04:07:11PM -0700, Benjamin De Kosnik wrote:
> 
> > Looks good to me.  
> 
> Great, trunk patch in.
> 
> > Will you prepare corresponding patch for the 4.8
> > branch too (I guess it should be pretty much the same, not sure if it
> > should keep using typedef system_clock steady_clock as before for the
> > non-MONOTONIC configuration, or if it should just do the same thing
> > as trunk)?
> 
> Same thing, I think. Testing now, ok when it completes?

Yes, thanks.

	Jakub
Jakub Jelinek - May 26, 2013, 7:31 p.m.
On Sun, May 26, 2013 at 07:58:09AM +0200, Jakub Jelinek wrote:
> On Sat, May 25, 2013 at 04:07:11PM -0700, Benjamin De Kosnik wrote:
> > 
> > > Looks good to me.  
> > 
> > Great, trunk patch in.
> > 
> > > Will you prepare corresponding patch for the 4.8
> > > branch too (I guess it should be pretty much the same, not sure if it
> > > should keep using typedef system_clock steady_clock as before for the
> > > non-MONOTONIC configuration, or if it should just do the same thing
> > > as trunk)?
> > 
> > Same thing, I think. Testing now, ok when it completes?
> 
> Yes, thanks.

My bootstraps on x86_64-linux and i686-linux on 4.8 branch were ok, so I
went ahead and committed the backport of your patch (applied cleanly).

	Jakub

Patch


2013-05-24  Benjamin Kosnik  <bkoz@redhat.com>

        * include/std/chrono: Wrap clocks in inline namespace _V2.
        * src/c++11/chrono.cc: Same.
        * src/c++11/compatibility-chrono.cc: Revert to previous chrono.cc
        file, with default configure macros selected.

        * config/abi/pre/gnu.ver (GLIBCXX_3.4.19): Use symbols from inline
        namespace.
        * config/abi/post/x86_64-linux-gnu/baseline_symbols.txt: Fix up.

        * config/abi/post/i386-linux-gnu/baseline_symbols.txt: Regenerated.
        * config/abi/post/s390x-linux-gnu/baseline_symbols.txt: Regenerated.
        * config/abi/post/powerpc64-linux-gnu/baseline_symbols.txt:
        Regenerated.
        * config/abi/post/powerpc64-linux-gnu/32/baseline_symbols.txt:
        Regenerated.
        * config/abi/post/x86_64-linux-gnu/baseline_symbols.txt: Regenerated.
        * config/abi/post/x86_64-linux-gnu/32/baseline_symbols.txt:
        Regenerated.
        * config/abi/post/powerpc-linux-gnu/baseline_symbols.txt: Regenerated.
        * config/abi/post/s390-linux-gnu/baseline_symbols.txt: Regenerated.
        * config/abi/post/i486-linux-gnu/baseline_symbols.txt: Regenerated.
        * config/abi/post/solaris2.10/baseline_symbols.txt: Regenerated.
        * config/abi/post/solaris2.10/amd64/baseline_symbols.txt: Regenerated.
        * config/abi/post/solaris2.10/sparcv9/baseline_symbols.txt:
        Regenerated.
        * config/abi/post/solaris2.9/baseline_symbols.txt: Regenerated.
        * config/abi/post/solaris2.9/sparcv9/baseline_symbols.txt: Regenerated.


diff --git a/libstdc++-v3/config/abi/post/i386-linux-gnu/baseline_symbols.txt b/libstdc++-v3/config/abi/post/i386-linux-gnu/baseline_symbols.txt
index 6a823ad..6876176 100644
--- a/libstdc++-v3/config/abi/post/i386-linux-gnu/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/i386-linux-gnu/baseline_symbols.txt
@@ -1937,9 +1937,9 @@  FUNC:_ZNSt6__norm15_List_node_base7_M_hookEPS0_@@GLIBCXX_3.4.14
 FUNC:_ZNSt6__norm15_List_node_base7reverseEv@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base8transferEPS0_S1_@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
-FUNC:_ZNSt6chrono12steady_clock3nowEv@@GLIBCXX_3.4.19
-FUNC:_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17
 FUNC:_ZNSt6chrono12system_clock3nowEv@@GLIBCXX_3.4.11
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6gslice8_IndexerC1EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6gslice8_IndexerC2EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6locale11_M_coalesceERKS_S1_i@@GLIBCXX_3.4
@@ -3018,6 +3018,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt10adopt_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt10defer_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt11try_to_lock@@GLIBCXX_3.4.11
diff --git a/libstdc++-v3/config/abi/post/i486-linux-gnu/baseline_symbols.txt b/libstdc++-v3/config/abi/post/i486-linux-gnu/baseline_symbols.txt
index 6a823ad..6876176 100644
--- a/libstdc++-v3/config/abi/post/i486-linux-gnu/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/i486-linux-gnu/baseline_symbols.txt
@@ -1937,9 +1937,9 @@  FUNC:_ZNSt6__norm15_List_node_base7_M_hookEPS0_@@GLIBCXX_3.4.14
 FUNC:_ZNSt6__norm15_List_node_base7reverseEv@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base8transferEPS0_S1_@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
-FUNC:_ZNSt6chrono12steady_clock3nowEv@@GLIBCXX_3.4.19
-FUNC:_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17
 FUNC:_ZNSt6chrono12system_clock3nowEv@@GLIBCXX_3.4.11
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6gslice8_IndexerC1EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6gslice8_IndexerC2EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6locale11_M_coalesceERKS_S1_i@@GLIBCXX_3.4
@@ -3018,6 +3018,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt10adopt_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt10defer_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt11try_to_lock@@GLIBCXX_3.4.11
diff --git a/libstdc++-v3/config/abi/post/powerpc-linux-gnu/baseline_symbols.txt b/libstdc++-v3/config/abi/post/powerpc-linux-gnu/baseline_symbols.txt
index 6a15139..dd45ef0 100644
--- a/libstdc++-v3/config/abi/post/powerpc-linux-gnu/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/powerpc-linux-gnu/baseline_symbols.txt
@@ -2127,9 +2127,9 @@  FUNC:_ZNSt6__norm15_List_node_base7_M_hookEPS0_@@GLIBCXX_3.4.14
 FUNC:_ZNSt6__norm15_List_node_base7reverseEv@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base8transferEPS0_S1_@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
-FUNC:_ZNSt6chrono12steady_clock3nowEv@@GLIBCXX_3.4.19
-FUNC:_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17
 FUNC:_ZNSt6chrono12system_clock3nowEv@@GLIBCXX_3.4.11
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6gslice8_IndexerC1EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6gslice8_IndexerC2EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6locale11_M_coalesceERKS_S1_i@@GLIBCXX_3.4
@@ -3278,6 +3278,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt10adopt_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt10defer_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt11try_to_lock@@GLIBCXX_3.4.11
diff --git a/libstdc++-v3/config/abi/post/powerpc64-linux-gnu/32/baseline_symbols.txt b/libstdc++-v3/config/abi/post/powerpc64-linux-gnu/32/baseline_symbols.txt
index 6a15139..dd45ef0 100644
--- a/libstdc++-v3/config/abi/post/powerpc64-linux-gnu/32/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/powerpc64-linux-gnu/32/baseline_symbols.txt
@@ -2127,9 +2127,9 @@  FUNC:_ZNSt6__norm15_List_node_base7_M_hookEPS0_@@GLIBCXX_3.4.14
 FUNC:_ZNSt6__norm15_List_node_base7reverseEv@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base8transferEPS0_S1_@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
-FUNC:_ZNSt6chrono12steady_clock3nowEv@@GLIBCXX_3.4.19
-FUNC:_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17
 FUNC:_ZNSt6chrono12system_clock3nowEv@@GLIBCXX_3.4.11
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6gslice8_IndexerC1EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6gslice8_IndexerC2EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6locale11_M_coalesceERKS_S1_i@@GLIBCXX_3.4
@@ -3278,6 +3278,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt10adopt_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt10defer_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt11try_to_lock@@GLIBCXX_3.4.11
diff --git a/libstdc++-v3/config/abi/post/powerpc64-linux-gnu/baseline_symbols.txt b/libstdc++-v3/config/abi/post/powerpc64-linux-gnu/baseline_symbols.txt
index ac5fe54..bc72230 100644
--- a/libstdc++-v3/config/abi/post/powerpc64-linux-gnu/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/powerpc64-linux-gnu/baseline_symbols.txt
@@ -2127,9 +2127,9 @@  FUNC:_ZNSt6__norm15_List_node_base7_M_hookEPS0_@@GLIBCXX_3.4.14
 FUNC:_ZNSt6__norm15_List_node_base7reverseEv@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base8transferEPS0_S1_@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
-FUNC:_ZNSt6chrono12steady_clock3nowEv@@GLIBCXX_3.4.19
-FUNC:_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17
 FUNC:_ZNSt6chrono12system_clock3nowEv@@GLIBCXX_3.4.11
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6gslice8_IndexerC1EmRKSt8valarrayImES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6gslice8_IndexerC2EmRKSt8valarrayImES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6locale11_M_coalesceERKS_S1_i@@GLIBCXX_3.4
@@ -3208,6 +3208,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt10adopt_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt10defer_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt11try_to_lock@@GLIBCXX_3.4.11
diff --git a/libstdc++-v3/config/abi/post/s390-linux-gnu/baseline_symbols.txt b/libstdc++-v3/config/abi/post/s390-linux-gnu/baseline_symbols.txt
index ca25208..3815db3 100644
--- a/libstdc++-v3/config/abi/post/s390-linux-gnu/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/s390-linux-gnu/baseline_symbols.txt
@@ -2127,9 +2127,9 @@  FUNC:_ZNSt6__norm15_List_node_base7_M_hookEPS0_@@GLIBCXX_3.4.14
 FUNC:_ZNSt6__norm15_List_node_base7reverseEv@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base8transferEPS0_S1_@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
-FUNC:_ZNSt6chrono12steady_clock3nowEv@@GLIBCXX_3.4.19
-FUNC:_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17
 FUNC:_ZNSt6chrono12system_clock3nowEv@@GLIBCXX_3.4.11
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6gslice8_IndexerC1EmRKSt8valarrayImES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6gslice8_IndexerC2EmRKSt8valarrayImES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6locale11_M_coalesceERKS_S1_i@@GLIBCXX_3.4
@@ -3278,6 +3278,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt10adopt_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt10defer_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt11try_to_lock@@GLIBCXX_3.4.11
diff --git a/libstdc++-v3/config/abi/post/s390x-linux-gnu/baseline_symbols.txt b/libstdc++-v3/config/abi/post/s390x-linux-gnu/baseline_symbols.txt
index ac5fe54..bc72230 100644
--- a/libstdc++-v3/config/abi/post/s390x-linux-gnu/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/s390x-linux-gnu/baseline_symbols.txt
@@ -2127,9 +2127,9 @@  FUNC:_ZNSt6__norm15_List_node_base7_M_hookEPS0_@@GLIBCXX_3.4.14
 FUNC:_ZNSt6__norm15_List_node_base7reverseEv@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base8transferEPS0_S1_@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
-FUNC:_ZNSt6chrono12steady_clock3nowEv@@GLIBCXX_3.4.19
-FUNC:_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17
 FUNC:_ZNSt6chrono12system_clock3nowEv@@GLIBCXX_3.4.11
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6gslice8_IndexerC1EmRKSt8valarrayImES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6gslice8_IndexerC2EmRKSt8valarrayImES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6locale11_M_coalesceERKS_S1_i@@GLIBCXX_3.4
@@ -3208,6 +3208,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt10adopt_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt10defer_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt11try_to_lock@@GLIBCXX_3.4.11
diff --git a/libstdc++-v3/config/abi/post/solaris2.10/amd64/baseline_symbols.txt b/libstdc++-v3/config/abi/post/solaris2.10/amd64/baseline_symbols.txt
index 5b46247..fb58c48 100644
--- a/libstdc++-v3/config/abi/post/solaris2.10/amd64/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/solaris2.10/amd64/baseline_symbols.txt
@@ -1902,8 +1902,9 @@  FUNC:_ZNSt6__norm15_List_node_base7_M_hookEPS0_@@GLIBCXX_3.4.14
 FUNC:_ZNSt6__norm15_List_node_base7reverseEv@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base8transferEPS0_S1_@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
-FUNC:_ZNSt6chrono12steady_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6chrono12system_clock3nowEv@@GLIBCXX_3.4.11
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6gslice8_IndexerC1EmRKSt8valarrayImES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6gslice8_IndexerC2EmRKSt8valarrayImES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6locale11_M_coalesceERKS_S1_i@@GLIBCXX_3.4
@@ -2915,6 +2916,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt7nothrow@@GLIBCXX_3.4
 OBJECT:20:_ZTSSt12ctype_bynameIcE@@GLIBCXX_3.4
 OBJECT:20:_ZTSSt12ctype_bynameIwE@@GLIBCXX_3.4
diff --git a/libstdc++-v3/config/abi/post/solaris2.10/baseline_symbols.txt b/libstdc++-v3/config/abi/post/solaris2.10/baseline_symbols.txt
index df69ba2..4b04784 100644
--- a/libstdc++-v3/config/abi/post/solaris2.10/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/solaris2.10/baseline_symbols.txt
@@ -1902,8 +1902,9 @@  FUNC:_ZNSt6__norm15_List_node_base7_M_hookEPS0_@@GLIBCXX_3.4.14
 FUNC:_ZNSt6__norm15_List_node_base7reverseEv@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base8transferEPS0_S1_@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
-FUNC:_ZNSt6chrono12steady_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6chrono12system_clock3nowEv@@GLIBCXX_3.4.11
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6gslice8_IndexerC1EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6gslice8_IndexerC2EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6locale11_M_coalesceERKS_S1_i@@GLIBCXX_3.4
@@ -2980,6 +2981,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt7nothrow@@GLIBCXX_3.4
 OBJECT:20:_ZTSSt12ctype_bynameIcE@@GLIBCXX_3.4
 OBJECT:20:_ZTSSt12ctype_bynameIwE@@GLIBCXX_3.4
diff --git a/libstdc++-v3/config/abi/post/solaris2.10/sparcv9/baseline_symbols.txt b/libstdc++-v3/config/abi/post/solaris2.10/sparcv9/baseline_symbols.txt
index 4c15813..d324ca0 100644
--- a/libstdc++-v3/config/abi/post/solaris2.10/sparcv9/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/solaris2.10/sparcv9/baseline_symbols.txt
@@ -1566,6 +1566,8 @@  FUNC:_ZNSt15_List_node_base7_M_hookEPS_@@GLIBCXX_3.4.14
 FUNC:_ZNSt15_List_node_base7reverseEv@@GLIBCXX_3.4
 FUNC:_ZNSt15_List_node_base8transferEPS_S0_@@GLIBCXX_3.4
 FUNC:_ZNSt15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt15__exception_ptr13exception_ptr4swapERS0_@@CXXABI_1.3.3
 FUNC:_ZNSt15__exception_ptr13exception_ptrC1EMS0_FvvE@@CXXABI_1.3.3
 FUNC:_ZNSt15__exception_ptr13exception_ptrC1ERKS0_@@CXXABI_1.3.3
@@ -2915,6 +2917,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt7nothrow@@GLIBCXX_3.4
 OBJECT:20:_ZTSSt12ctype_bynameIcE@@GLIBCXX_3.4
 OBJECT:20:_ZTSSt12ctype_bynameIwE@@GLIBCXX_3.4
diff --git a/libstdc++-v3/config/abi/post/solaris2.9/baseline_symbols.txt b/libstdc++-v3/config/abi/post/solaris2.9/baseline_symbols.txt
index b9e822e..63c0ec5 100644
--- a/libstdc++-v3/config/abi/post/solaris2.9/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/solaris2.9/baseline_symbols.txt
@@ -1878,8 +1878,9 @@  FUNC:_ZNSt6__norm15_List_node_base7_M_hookEPS0_@@GLIBCXX_3.4.14
 FUNC:_ZNSt6__norm15_List_node_base7reverseEv@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base8transferEPS0_S1_@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
-FUNC:_ZNSt6chrono12steady_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6chrono12system_clock3nowEv@@GLIBCXX_3.4.11
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6gslice8_IndexerC1EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6gslice8_IndexerC2EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6locale11_M_coalesceERKS_S1_i@@GLIBCXX_3.4
@@ -2991,6 +2992,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt7nothrow@@GLIBCXX_3.4
 OBJECT:20:_ZTSSt12ctype_bynameIcE@@GLIBCXX_3.4
 OBJECT:20:_ZTSSt12ctype_bynameIwE@@GLIBCXX_3.4
diff --git a/libstdc++-v3/config/abi/post/solaris2.9/sparcv9/baseline_symbols.txt b/libstdc++-v3/config/abi/post/solaris2.9/sparcv9/baseline_symbols.txt
index 3a3d0b7..d4bcf7e 100644
--- a/libstdc++-v3/config/abi/post/solaris2.9/sparcv9/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/solaris2.9/sparcv9/baseline_symbols.txt
@@ -1878,8 +1878,9 @@  FUNC:_ZNSt6__norm15_List_node_base7_M_hookEPS0_@@GLIBCXX_3.4.14
 FUNC:_ZNSt6__norm15_List_node_base7reverseEv@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base8transferEPS0_S1_@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
-FUNC:_ZNSt6chrono12steady_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6chrono12system_clock3nowEv@@GLIBCXX_3.4.11
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6gslice8_IndexerC1EmRKSt8valarrayImES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6gslice8_IndexerC2EmRKSt8valarrayImES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6locale11_M_coalesceERKS_S1_i@@GLIBCXX_3.4
@@ -2926,6 +2927,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt7nothrow@@GLIBCXX_3.4
 OBJECT:20:_ZTSSt12ctype_bynameIcE@@GLIBCXX_3.4
 OBJECT:20:_ZTSSt12ctype_bynameIwE@@GLIBCXX_3.4
diff --git a/libstdc++-v3/config/abi/post/x86_64-linux-gnu/32/baseline_symbols.txt b/libstdc++-v3/config/abi/post/x86_64-linux-gnu/32/baseline_symbols.txt
index 6a823ad..6876176 100644
--- a/libstdc++-v3/config/abi/post/x86_64-linux-gnu/32/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/x86_64-linux-gnu/32/baseline_symbols.txt
@@ -1937,9 +1937,9 @@  FUNC:_ZNSt6__norm15_List_node_base7_M_hookEPS0_@@GLIBCXX_3.4.14
 FUNC:_ZNSt6__norm15_List_node_base7reverseEv@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base8transferEPS0_S1_@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
-FUNC:_ZNSt6chrono12steady_clock3nowEv@@GLIBCXX_3.4.19
-FUNC:_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17
 FUNC:_ZNSt6chrono12system_clock3nowEv@@GLIBCXX_3.4.11
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6gslice8_IndexerC1EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6gslice8_IndexerC2EjRKSt8valarrayIjES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6locale11_M_coalesceERKS_S1_i@@GLIBCXX_3.4
@@ -3018,6 +3018,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt10adopt_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt10defer_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt11try_to_lock@@GLIBCXX_3.4.11
diff --git a/libstdc++-v3/config/abi/post/x86_64-linux-gnu/baseline_symbols.txt b/libstdc++-v3/config/abi/post/x86_64-linux-gnu/baseline_symbols.txt
index 165638b..0217375 100644
--- a/libstdc++-v3/config/abi/post/x86_64-linux-gnu/baseline_symbols.txt
+++ b/libstdc++-v3/config/abi/post/x86_64-linux-gnu/baseline_symbols.txt
@@ -1937,9 +1937,9 @@  FUNC:_ZNSt6__norm15_List_node_base7_M_hookEPS0_@@GLIBCXX_3.4.14
 FUNC:_ZNSt6__norm15_List_node_base7reverseEv@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base8transferEPS0_S1_@@GLIBCXX_3.4.9
 FUNC:_ZNSt6__norm15_List_node_base9_M_unhookEv@@GLIBCXX_3.4.14
-FUNC:_ZNSt6chrono12steady_clock3nowEv@@GLIBCXX_3.4.19
-FUNC:_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17
 FUNC:_ZNSt6chrono12system_clock3nowEv@@GLIBCXX_3.4.11
+FUNC:_ZNSt6chrono3_V212steady_clock3nowEv@@GLIBCXX_3.4.19
+FUNC:_ZNSt6chrono3_V212system_clock3nowEv@@GLIBCXX_3.4.19
 FUNC:_ZNSt6gslice8_IndexerC1EmRKSt8valarrayImES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6gslice8_IndexerC2EmRKSt8valarrayImES4_@@GLIBCXX_3.4
 FUNC:_ZNSt6locale11_M_coalesceERKS_S1_i@@GLIBCXX_3.4
@@ -2953,6 +2953,8 @@  OBJECT:1:_ZNSt21__numeric_limits_base9is_iec559E@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_moduloE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt21__numeric_limits_base9is_signedE@@GLIBCXX_3.4
 OBJECT:1:_ZNSt6chrono12system_clock12is_monotonicE@@GLIBCXX_3.4.11
+OBJECT:1:_ZNSt6chrono3_V212steady_clock9is_steadyE@@GLIBCXX_3.4.19
+OBJECT:1:_ZNSt6chrono3_V212system_clock9is_steadyE@@GLIBCXX_3.4.19
 OBJECT:1:_ZSt10adopt_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt10defer_lock@@GLIBCXX_3.4.11
 OBJECT:1:_ZSt11try_to_lock@@GLIBCXX_3.4.11
diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver
index 9c64a0d..9e1f4da 100644
--- a/libstdc++-v3/config/abi/pre/gnu.ver
+++ b/libstdc++-v3/config/abi/pre/gnu.ver
@@ -1320,11 +1320,8 @@  GLIBCXX_3.4.17 {
     _ZNSt13__future_base19_Async_state_commonD1Ev;
     _ZNSt13__future_base19_Async_state_commonD2Ev;
 
-#ifdef HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT
-   # GLIBCXX_ABI compatibility only.
     # std::chrono::steady_clock::now()
     _ZNSt6chrono12steady_clock3nowEv;
-#endif
 
 } GLIBCXX_3.4.16;
 
@@ -1349,8 +1346,11 @@  GLIBCXX_3.4.18 {
 
 GLIBCXX_3.4.19 {
 
-    # std::chrono::steady_clock::now()
-    _ZNSt6chrono12steady_clock3nowEv;
+    # chrono second generation
+    _ZNSt6chrono3_V212steady_clock3nowEv;
+    _ZNSt6chrono3_V212steady_clock9is_steadyE;
+    _ZNSt6chrono3_V212system_clock3nowEv;
+    _ZNSt6chrono3_V212system_clock9is_steadyE;
 
 } GLIBCXX_3.4.18;
 
diff --git a/libstdc++-v3/include/std/chrono b/libstdc++-v3/include/std/chrono
index 7111319..6d9df7d 100644
--- a/libstdc++-v3/include/std/chrono
+++ b/libstdc++-v3/include/std/chrono
@@ -686,17 +686,35 @@  _GLIBCXX_END_NAMESPACE_VERSION
 		 const time_point<_Clock, _Dur2>& __rhs)
       { return !(__lhs < __rhs); }
 
-    /// system_clock
-    struct system_clock
+
+    // Clocks. 
+
+    // Why nanosecond resolution as the default?  
+    // Why have std::system_clock always count in the higest
+    // resolution (ie nanoseconds), even if on some OSes the low 3
+    // or 9 decimal digits will be always zero? This allows later
+    // implementations to change the system_clock::now()
+    // implementation any time to provide better resolution without
+    // changing function signature or units.
+
+    // To support the (forward) evolution of the library's defined
+    // clocks, wrap inside inline namespace so that the current
+    // defintions of system_clock, steady_clock, and
+    // high_resolution_clock types are uniquely mangled. This way, new
+    // code can use the latests clocks, while the library can contain
+    // compatibility definitions for previous versions.  At some
+    // point, when these clocks settle down, the inlined namespaces
+    // can be removed.  XXX GLIBCXX_ABI Deprecated
+    inline namespace _V2 {
+
+    /**
+     *  @brief System clock.
+     *
+     *  Time returned represents wall time from the system-wide clock.
+    */
+     struct system_clock
     {
-#ifdef _GLIBCXX_USE_CLOCK_REALTIME
       typedef chrono::nanoseconds     				duration;
-#elif defined(_GLIBCXX_USE_GETTIMEOFDAY)
-      typedef chrono::microseconds    				duration;
-#else
-      typedef chrono::seconds	      				duration;
-#endif
-
       typedef duration::rep    					rep;
       typedef duration::period 					period;
       typedef chrono::time_point<system_clock, duration> 	time_point;
@@ -727,8 +745,12 @@  _GLIBCXX_END_NAMESPACE_VERSION
       }
     };
 
-#ifdef _GLIBCXX_USE_CLOCK_MONOTONIC
-    /// steady_clock
+
+    /**
+     *  @brief Monotonic clock
+     *
+     *  Time returned has the property of only increasing at a uniform rate.
+    */
     struct steady_clock
     {
       typedef chrono::nanoseconds 				duration;
@@ -741,11 +763,18 @@  _GLIBCXX_END_NAMESPACE_VERSION
       static time_point
       now() noexcept;
     };
-#else
-    typedef system_clock steady_clock;
-#endif
 
-    typedef system_clock high_resolution_clock;
+
+    /**
+     *  @brief Highest-resolution clock
+     *
+     *  This is the clock "with the shortest tick period." Alias to
+     *  std::system_clock until higher-than-nanosecond definitions
+     *  become feasible.
+    */
+    using high_resolution_clock = system_clock;
+
+  } // end inline namespace _V2
 
   _GLIBCXX_END_NAMESPACE_VERSION
   } // namespace chrono
diff --git a/libstdc++-v3/src/c++11/chrono.cc b/libstdc++-v3/src/c++11/chrono.cc
index 15de4eb..ca10fb3 100644
--- a/libstdc++-v3/src/c++11/chrono.cc
+++ b/libstdc++-v3/src/c++11/chrono.cc
@@ -23,28 +23,17 @@ 
 // <http://www.gnu.org/licenses/>.
 
 #include <bits/c++config.h>
-
-#ifndef _GLIBCXX_USE_CLOCK_MONOTONIC
-// If !_GLIBCXX_USE_CLOCK_MONOTONIC, std::chrono::steady_clock
-// is just a typedef to std::chrono::system_clock, for ABI compatibility
-// force it not to be a typedef now and export it anyway.  Programs
-// using the headers where it is a typedef will actually just use
-// std::chrono::system_clock instead, and this remains here just as a fallback.
-#define _GLIBCXX_USE_CLOCK_MONOTONIC
-#include <chrono>
-#undef _GLIBCXX_USE_CLOCK_MONOTONIC
-#else
 #include <chrono>
-#endif
 
 #ifdef _GLIBCXX_USE_C99_STDINT_TR1
 
-// conditional inclusion of sys/time.h for gettimeofday
+// Conditional inclusion of sys/time.h for gettimeofday
 #if !defined(_GLIBCXX_USE_CLOCK_MONOTONIC) && \
     !defined(_GLIBCXX_USE_CLOCK_REALTIME) && \
      defined(_GLIBCXX_USE_GETTIMEOFDAY)
 #include <sys/time.h>
 #endif
+
 #ifdef _GLIBCXX_USE_CLOCK_GETTIME_SYSCALL
 #include <unistd.h>
 #include <sys/syscall.h>
@@ -56,7 +45,9 @@  namespace std _GLIBCXX_VISIBILITY(default)
   {
   _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
-#ifndef _GLIBCXX_COMPATIBILITY_CXX0X
+    // XXX GLIBCXX_ABI Deprecated
+    inline namespace _V2 {
+
     constexpr bool system_clock::is_steady;
 
     system_clock::time_point
@@ -83,18 +74,10 @@  namespace std _GLIBCXX_VISIBILITY(default)
       return system_clock::from_time_t(__sec);
 #endif
     }
-#endif
+
     
-#ifndef _GLIBCXX_COMPATIBILITY_CXX0X
     constexpr bool steady_clock::is_steady;
-#endif
 
-#if defined(_GLIBCXX_SYMVER_GNU) && defined(_GLIBCXX_SHARED) \
-    && defined(_GLIBCXX_HAVE_AS_SYMVER_DIRECTIVE) \
-    && defined(_GLIBCXX_HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT) \
-    && !defined(_GLIBCXX_COMPATIBILITY_CXX0X)
-    __attribute__((__weak__))
-#endif
     steady_clock::time_point
     steady_clock::now() noexcept
     {
@@ -113,6 +96,8 @@  namespace std _GLIBCXX_VISIBILITY(default)
 #endif
     }
 
+  } // end inline namespace _V2
+
   _GLIBCXX_END_NAMESPACE_VERSION
   } // namespace chrono
 } // namespace std
diff --git a/libstdc++-v3/src/c++11/compatibility-chrono.cc b/libstdc++-v3/src/c++11/compatibility-chrono.cc
index ada0946..fd67dae 100644
--- a/libstdc++-v3/src/c++11/compatibility-chrono.cc
+++ b/libstdc++-v3/src/c++11/compatibility-chrono.cc
@@ -22,37 +22,68 @@ 
 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 // <http://www.gnu.org/licenses/>.
 
-#define _GLIBCXX_COMPATIBILITY_CXX0X
 #include <bits/c++config.h>
 
-#if defined(_GLIBCXX_SYMVER_GNU) && defined(_GLIBCXX_SHARED) \
-    && defined(_GLIBCXX_HAVE_AS_SYMVER_DIRECTIVE)\
-    && defined(_GLIBCXX_HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT)
+#ifdef _GLIBCXX_USE_C99_STDINT_TR1
 
+#ifdef _GLIBCXX_USE_GETTIMEOFDAY
+#include <sys/time.h>
+#endif
+
+#define system_clock system_clockXX
 #define steady_clock steady_clockXX
-#include "chrono.cc"
-
-// The rename syntax for default exported names is
-//   asm (".symver name1,exportedname@GLIBCXX_3.4.17")
-//   asm (".symver name2,exportedname@@GLIBCXX_3.4.19")
-// In the future, GLIBCXX_ABI > 6 should remove all uses of
-// _GLIBCXX_*_SYMVER macros in this file.
-
-#define _GLIBCXX_3_4_17_SYMVER(XXname, name) \
-   extern "C" void \
-   _X##name() \
-   __attribute__ ((alias(#XXname))); \
-   asm (".symver " "_X" #name "," #name "@GLIBCXX_3.4.17");
-
-#define _GLIBCXX_3_4_19_SYMVER(XXname, name) \
-   extern "C" void \
-   _Y##name() \
-   __attribute__ ((alias(#XXname))); \
-   asm (".symver " "_Y" #name  "," #name "@@GLIBCXX_3.4.19");
-
-_GLIBCXX_3_4_17_SYMVER(_ZNSt6chrono14steady_clockXX3nowEv,
-		       _ZNSt6chrono12steady_clock3nowEv)
-_GLIBCXX_3_4_19_SYMVER(_ZNSt6chrono14steady_clockXX3nowEv,
-		       _ZNSt6chrono12steady_clock3nowEv)
+#include <chrono>
+#undef system_clock
+#undef steady_clock
 
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+  namespace chrono
+  {
+  _GLIBCXX_BEGIN_NAMESPACE_VERSION
+ 
+    // NB: Default configuration was no realtime.
+    struct system_clock
+    {
+#ifdef _GLIBCXX_USE_GETTIMEOFDAY
+      typedef chrono::microseconds    				duration;
+#else
+      typedef chrono::seconds	      				duration;
 #endif
+
+      typedef duration::rep    					rep;
+      typedef duration::period 					period;
+      typedef chrono::time_point<system_clock, duration> 	time_point;
+
+      static_assert(system_clock::duration::min()
+		    < system_clock::duration::zero(),
+		    "a clock's minimum duration cannot be less than its epoch");
+
+      static constexpr bool is_steady = false;
+
+      static time_point
+      now() noexcept;
+    };
+
+    constexpr bool system_clock::is_steady;
+
+    system_clock::time_point
+    system_clock::now() noexcept
+    {
+#ifdef _GLIBCXX_USE_GETTIMEOFDAY
+      timeval tv;
+      // EINVAL, EFAULT
+      gettimeofday(&tv, 0);
+      return time_point(duration(chrono::seconds(tv.tv_sec)
+				 + chrono::microseconds(tv.tv_usec)));
+#else
+      std::time_t __sec = std::time(0);
+      return system_clock::from_time_t(__sec);
+#endif
+    }
+
+  _GLIBCXX_END_NAMESPACE_VERSION
+  } // namespace chrono
+} // namespace std
+
+#endif // _GLIBCXX_USE_C99_STDINT_TR1