Test that we can see the stackframe (including top frame var) of a st…

…epping process

Summary:
This checks in particular that we don't require to hit a user breakpoint in order to resolve variables (that used to be the case before the introduction of `edb_server_break:is_trapped`).

We add a dummy function that computes some arithmetic to avoid the current quirks of stepping in recursive functions.

Reviewed By: jcpetruzza

Differential Revision: D68508670

fbshipit-source-id: c3c51b3a918bb89f3741e79e96ea97e0cabd0f85

test/edb_SUITE.erl

@@ -68,6 +68,7 @@
 %% Test cases for the test_stackframes group
 -export([test_shows_stackframes_of_process_in_breakpoint/1]).
 -export([test_shows_stackframes_of_paused_processes_not_in_breakpoint/1]).
+-export([test_shows_stackframes_of_stepping_process/1]).
 -export([test_can_control_max_size_of_terms_in_vars_for_process_in_bp/1]).
 -export([test_can_control_max_size_of_terms_in_vars_for_process_not_in_bp/1]).
 -export([test_doesnt_show_stackframes_for_running_processes/1]).
@@ -126,6 +127,7 @@ groups() ->
         {test_stackframes, [], [
             test_shows_stackframes_of_process_in_breakpoint,
             test_shows_stackframes_of_paused_processes_not_in_breakpoint,
+            test_shows_stackframes_of_stepping_process,
             test_can_control_max_size_of_terms_in_vars_for_process_in_bp,
             test_can_control_max_size_of_terms_in_vars_for_process_not_in_bp,
             test_doesnt_show_stackframes_for_running_processes,
@@ -2094,6 +2096,64 @@ test_shows_stackframes_of_paused_processes_not_in_breakpoint(Config) ->
     ),
     ok.
 
+test_shows_stackframes_of_stepping_process(Config) ->
+    TestModuleSource = proplists:get_value(erl_source, Config),
+
+    % Stop before computing 42
+    ok = edb:add_breakpoint(test_stackframes, 38),
+
+    % Spawn a process that will hit this breakpoint
+    Pid = erlang:spawn(test_stackframes, forty_two, []),
+    {ok, stopped} = edb:wait(),
+
+    % Step to the next line
+    ok = edb:step_over(Pid),
+    {ok, stopped} = edb:wait(),
+
+    % Check that we can see the stack frames
+    {ok, Frames} = edb:stack_frames(Pid),
+    ?assertEqual(
+        [
+            % forty_two(1337)
+            #{id => 2, mfa => {test_stackframes, forty_two, 1}, source => TestModuleSource, line => 39},
+            % forty_two()
+            #{id => 1, mfa => {test_stackframes, forty_two, 0}, source => TestModuleSource, line => 34}
+        ],
+        Frames
+    ),
+
+    % Can't select the step frame
+    ?assertEqual(
+        undefined,
+        edb:stack_frame_vars(Pid, 3)
+    ),
+
+    % Can see variables in the top frame
+    ?assertEqual(
+        {ok, #{
+            vars => #{
+                <<"X">> => {value, 1337},
+                <<"Six">> => {value, 6},
+                <<"FortyTwo">> => {value, 42}
+            },
+            xregs => [
+                {value, 1337}
+            ],
+            yregs => []
+        }},
+        edb:stack_frame_vars(Pid, 2)
+    ),
+
+    % Sanity check that we can select the bottom frame
+    ?assertEqual(
+        {ok, #{
+            yregs => []
+        }},
+        edb:stack_frame_vars(Pid, 1)
+    ),
+
+    ok.
+
 test_can_control_max_size_of_terms_in_vars_for_process_in_bp(_Config) ->
     % stop in hang() call
     ok = edb:add_breakpoint(test_stackframes, 31),

test/edb_SUITE_data/test_stackframes.erl

@@ -1,5 +1,5 @@
 -module(test_stackframes). %01
--export([choose/2, ping/1, pong/0, hang/3]). %02
+-export([choose/2, ping/1, pong/0, hang/3, forty_two/0]). %02
 
 choose(N, K) when N =:= K -> %04
     N div K; %05 (convoluted way to say 1, to have N and K "alive")
@@ -29,3 +29,12 @@ pong() -> %23
 
 hang(X, Y, Z) -> %30
     hang(X, Y, Z). %31
+
+forty_two() -> %33
+    0 + forty_two(1337). %34 (force a non-tail call)
+
+forty_two(X) -> %36
+    Six = 6, %37
+    FortyTwo = Six * 7, %38
+    _KeepXAlive = X + X, %39 (force X to be alive)
+    FortyTwo. %40