Add system_info(atom_limit)

Add system_info(atom_limit) to provide a way to retrieve the maximum
number of atoms allowed. Add tests and documentation for it too.

Also split system_info_SUITE:start_node/2 to start_node_ets/2 and
start_node_atm/2 to avoid code duplication.

4 files changed, 57 insertions, 12 deletions

diff --git a/erts/emulator/beam/atom.c b/erts/emulator/beam/atom.c
index a5e778e4aa..d2fad24805 100644
--- a/erts/emulator/beam/atom.c
+++ b/erts/emulator/beam/atom.c
@@ -483,3 +483,9 @@ dump_atoms(int to, void *to_arg)
 	}
     }
 }
+
+Uint
+erts_get_atom_limit(void)
+{
+    return erts_atom_table.limit;
+}
\ No newline at end of file
diff --git a/erts/emulator/beam/atom.h b/erts/emulator/beam/atom.h
index ae60904785..0d34c47a55 100644
--- a/erts/emulator/beam/atom.h
+++ b/erts/emulator/beam/atom.h
@@ -138,6 +138,7 @@ int atom_static_put(byte*, int);
 void init_atom_table(void);
 void atom_info(int, void *);
 void dump_atoms(int, void *);
+Uint erts_get_atom_limit(void);
 int erts_atom_get(const char* name, int len, Eterm* ap, ErtsAtomEncoding enc);
 void erts_atom_get_text_space_sizes(Uint *reserved, Uint *used);
 #endif
diff --git a/erts/emulator/beam/erl_bif_info.c b/erts/emulator/beam/erl_bif_info.c
index 29ba12dfdb..cfe01f244e 100644
--- a/erts/emulator/beam/erl_bif_info.c
+++ b/erts/emulator/beam/erl_bif_info.c
@@ -2859,6 +2859,9 @@ BIF_RETTYPE system_info_1(BIF_ALIST_1)
     else if (ERTS_IS_ATOM_STR("ets_limit",BIF_ARG_1)) {
         BIF_RET(make_small(erts_db_get_max_tabs()));
     }
+    else if (ERTS_IS_ATOM_STR("atom_limit",BIF_ARG_1)) {
+        BIF_RET(make_small(erts_get_atom_limit()));
+    }
     else if (ERTS_IS_ATOM_STR("tolerant_timeofday",BIF_ARG_1)) {
 	if (erts_has_time_correction()
 	    && erts_time_offset_state() == ERTS_TIME_OFFSET_FINAL) {
diff --git a/erts/emulator/test/system_info_SUITE.erl b/erts/emulator/test/system_info_SUITE.erl
index a4aedb31f6..3d9e74472b 100644
--- a/erts/emulator/test/system_info_SUITE.erl
+++ b/erts/emulator/test/system_info_SUITE.erl
@@ -36,7 +36,7 @@
 -export([all/0, suite/0]).
 
 -export([process_count/1, system_version/1, misc_smoke_tests/1,
-         heap_size/1, wordsize/1, memory/1, ets_limit/1]).
+         heap_size/1, wordsize/1, memory/1, ets_limit/1, atom_limit/1]).
 
 suite() ->
     [{ct_hooks,[ts_install_cth]},
@@ -44,7 +44,7 @@ suite() ->
 
 all() -> 
     [process_count, system_version, misc_smoke_tests,
-     heap_size, wordsize, memory, ets_limit].
+     heap_size, wordsize, memory, ets_limit, atom_limit].
 
 %%%
 %%% The test cases -------------------------------------------------------------
@@ -472,6 +472,17 @@ mapn(_Fun, 0) ->
 mapn(Fun, N) ->
     [Fun(N) | mapn(Fun, N-1)].
 
+
+get_node_name(Config) ->
+    list_to_atom(atom_to_list(?MODULE)
+		 ++ "-"
+		 ++ atom_to_list(proplists:get_value(testcase, Config))
+		 ++ "-"
+		 ++ integer_to_list(erlang:system_time(second))
+		 ++ "-"
+		 ++ integer_to_list(erlang:unique_integer([positive]))).
+
+
 %% Verify system_info(ets_limit) reflects max ETS table settings.
 ets_limit(Config0) when is_list(Config0) ->
     Config = [{testcase,ets_limit}|Config0],
@@ -486,7 +497,7 @@ get_ets_limit(Config, EtsMax) ->
                0 -> [];
                _ -> [{"ERL_MAX_ETS_TABLES", integer_to_list(EtsMax)}]
            end,
-    {ok, Node} = start_node(Config, Envs),
+    {ok, Node} = start_node_ets(Config, Envs),
     Me = self(),
     Ref = make_ref(),
     spawn_link(Node,
@@ -502,16 +513,40 @@ get_ets_limit(Config, EtsMax) ->
     stop_node(Node),
     Res.
 
-start_node(Config, Envs) when is_list(Config) ->
+start_node_ets(Config, Envs) when is_list(Config) ->
+    Pa = filename:dirname(code:which(?MODULE)),
+    test_server:start_node(get_node_name(Config), peer,
+			   [{args, "-pa "++Pa}, {env, Envs}]).
+
+start_node_atm(Config, AtomsMax) when is_list(Config) ->
     Pa = filename:dirname(code:which(?MODULE)),
-    Name = list_to_atom(atom_to_list(?MODULE)
-                        ++ "-"
-                        ++ atom_to_list(proplists:get_value(testcase, Config))
-                        ++ "-"
-                        ++ integer_to_list(erlang:system_time(second))
-                        ++ "-"
-                        ++ integer_to_list(erlang:unique_integer([positive]))),
-    test_server:start_node(Name, peer, [{args, "-pa "++Pa}, {env, Envs}]).
+    test_server:start_node(get_node_name(Config), peer,
+			   [{args, "-pa "++ Pa ++ AtomsMax}]).
 
 stop_node(Node) ->
     test_server:stop_node(Node).
+
+
+%% Verify system_info(atom_limit) reflects max atoms settings
+%% (using " +t").
+atom_limit(Config0) when is_list(Config0) ->
+    Config = [{testcase,atom_limit}|Config0],
+    2186042 = get_atom_limit(Config, " +t 2186042 "),
+    ok.
+
+get_atom_limit(Config, AtomsMax) ->
+    {ok, Node} = start_node_atm(Config, AtomsMax),
+    Me = self(),
+    Ref = make_ref(),
+    spawn_link(Node,
+        fun() ->
+            Res = erlang:system_info(atom_limit),
+            unlink(Me),
+            Me ! {Ref, Res}
+        end),
+    receive
+        {Ref, Res} ->
+            Res
+    end,
+    stop_node(Node),
+    Res.