Introduce time warp safe replacement for safe_fixed option

The new time warp safe option is safe_fixed_monotonic_time which
gives erlang:monotonic_time().

The safe_fixed option was also slightly changed. It now gives
erlang:timestamp() instead of erlang:now(). This has however
not been documented, so it is considered a compatible change.

The above effects both ets, and dets.

This commit also include the bugfix OTP-13239 for
dets:info(Tab, safe_fixed). The timestamp in the result returned
by dets:info(Tab, safe_fixed) was unintentionally broken as a
result of the time API rewrites in OTP 18.0.

3 files changed, 30 insertions, 10 deletions

diff --git a/lib/stdlib/src/dets.erl b/lib/stdlib/src/dets.erl
index 6d07f4018a..2d037ff795 100644
--- a/lib/stdlib/src/dets.erl
+++ b/lib/stdlib/src/dets.erl
@@ -372,7 +372,7 @@ info(Tab) ->
       Item :: 'access' | 'auto_save' | 'bchunk_format'
             | 'hash' | 'file_size' | 'filename' | 'keypos' | 'memory'
             | 'no_keys' | 'no_objects' | 'no_slots' | 'owner' | 'ram_file'
-            | 'safe_fixed' | 'size' | 'type' | 'version',
+            | 'safe_fixed' | 'safe_fixed_monotonic_time' | 'size' | 'type' | 'version',
       Value :: term().
 
 info(Tab, owner) ->
@@ -1964,7 +1964,9 @@ do_safe_fixtable(Head, Pid, true) ->
     case Head#head.fixed of 
 	false -> 
 	    link(Pid),
-	    Fixed = {utime_now(), [{Pid, 1}]},
+	    MonTime = erlang:monotonic_time(),
+	    TimeOffset = erlang:time_offset(),
+	    Fixed = {{MonTime, TimeOffset}, [{Pid, 1}]},
 	    Ftab = dets_utils:get_freelists(Head),
 	    Head#head{fixed = Fixed, freelists = {Ftab, Ftab}};
 	{TimeStamp, Counters} ->
@@ -2091,7 +2093,22 @@ finfo(H, no_keys) ->
 finfo(H, no_slots) -> {H, (H#head.mod):no_slots(H)};
 finfo(H, pid) -> {H, self()};
 finfo(H, ram_file) -> {H, H#head.ram_file};
-finfo(H, safe_fixed) -> {H, H#head.fixed};
+finfo(H, safe_fixed) ->
+    {H,
+     case H#head.fixed of
+	 false ->
+	     false;
+	 {{FixMonTime, TimeOffset}, RefList} ->
+	     {make_timestamp(FixMonTime, TimeOffset), RefList}
+     end};
+finfo(H, safe_fixed_monotonic_time) ->
+    {H,
+     case H#head.fixed of
+	 false ->
+	     false;
+	 {{FixMonTime, _TimeOffset}, RefList} ->
+	     {FixMonTime, RefList}
+     end};
 finfo(H, size) -> 
     case catch write_cache(H) of
 	{H2, []} ->
@@ -3275,11 +3292,14 @@ err(Error) ->
 time_now() ->
     erlang:monotonic_time(1000000).
 
--compile({inline, [utime_now/0]}).
-utime_now() ->
-    Time = time_now(),
-    UniqueCounter = erlang:unique_integer([monotonic]),
-    {Time, UniqueCounter}.
+make_timestamp(MonTime, TimeOffset) ->
+    ErlangSystemTime = erlang:convert_time_unit(MonTime+TimeOffset,
+						native,
+						micro_seconds),
+    MegaSecs = ErlangSystemTime div 1000000000000,
+    Secs = ErlangSystemTime div 1000000 - MegaSecs*1000000,
+    MicroSecs = ErlangSystemTime rem 1000000,
+    {MegaSecs, Secs, MicroSecs}.
 
 %%%%%%%%%%%%%%%%%  DEBUG functions %%%%%%%%%%%%%%%%
 
diff --git a/lib/stdlib/src/ets.erl b/lib/stdlib/src/ets.erl
index 847def2fd8..1fca3624dc 100644
--- a/lib/stdlib/src/ets.erl
+++ b/lib/stdlib/src/ets.erl
@@ -146,7 +146,7 @@ info(_) ->
       Tab :: tab(),
       Item :: compressed | fixed | heir | keypos | memory
             | name | named_table | node | owner | protection
-            | safe_fixed | size | stats | type
+            | safe_fixed | safe_fixed_monotonic_time | size | stats | type
 	    | write_concurrency | read_concurrency,
       Value :: term().
 
diff --git a/lib/stdlib/src/stdlib.app.src b/lib/stdlib/src/stdlib.app.src
index 7f9bbbf649..b8a7973cf2 100644
--- a/lib/stdlib/src/stdlib.app.src
+++ b/lib/stdlib/src/stdlib.app.src
@@ -105,7 +105,7 @@
                dets]},
   {applications, [kernel]},
   {env, []},
-  {runtime_dependencies, ["sasl-2.6","kernel-4.1","erts-7.0","crypto-3.3",
+  {runtime_dependencies, ["sasl-2.6","kernel-4.1","erts-7.3","crypto-3.3",
 			  "compiler-5.0"]}
 ]}.