Merge branch 'john/misc-fixes-and-additions'

* john/misc-fixes-and-additions:
  beam_validator: Fail when trying to set the type of a dead value
  beam_validator: Fix bad comment formatting/wording
  erts: Assert that GC should not be disabled twice

2 files changed, 12 insertions, 14 deletions

diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index 1f6adb98ef..e69a9b8813 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -11019,8 +11019,13 @@ erts_set_gc_state(Process *c_p, int enable)
     ERTS_LC_ASSERT(ERTS_PROC_LOCK_MAIN == erts_proc_lc_my_proc_locks(c_p));
 
     if (!enable) {
-	c_p->flags |= F_DISABLE_GC;
-	return 0;
+        /* Strictly speaking it's not illegal to disable the GC when it's
+         * already disabled, but we risk enabling the GC prematurely if (for
+         * example) a BIF were to blindly disable it when trapping and then
+         * re-enable it before returning its result. */
+        ASSERT(!(c_p->flags & F_DISABLE_GC));
+        c_p->flags |= F_DISABLE_GC;
+        return 0;
     }
 
     c_p->flags &= ~F_DISABLE_GC;
diff --git a/lib/compiler/src/beam_validator.erl b/lib/compiler/src/beam_validator.erl
index b4acebbfae..0ae3b4ed1f 100644
--- a/lib/compiler/src/beam_validator.erl
+++ b/lib/compiler/src/beam_validator.erl
@@ -200,7 +200,7 @@ validate_0(Module, [{function,Name,Ar,Entry,Code}|Fs], Ft) ->
          numy=none :: none | undecided | index(),
          %% Available heap size.
          h=0,
-         %Available heap size for floats.
+         %%Available heap size for floats.
          hf=0,
          %% Floating point state.
          fls=undefined,
@@ -240,7 +240,7 @@ index_parameter_types([{function,_,_,Entry,Code0}|Fs], Acc0) ->
 	    Acc = index_parameter_types_1(Is, Entry, Acc0),
 	    index_parameter_types(Fs, Acc);
 	_ ->
-	    %% Something serious is wrong. Ignore it for now.
+	    %% Something is seriously wrong. Ignore it for now.
 	    %% It will be detected and diagnosed later.
 	    index_parameter_types(Fs, Acc0)
     end;
@@ -1865,16 +1865,9 @@ get_reg_vref({y,_}=Src, #vst{current=#st{ys=Ys}}) ->
     end.
 
 set_type(Type, #value_ref{}=Ref, #vst{current=#st{vs=Vs0}=St}=Vst) ->
-    case Vs0 of
-        #{ Ref := #value{}=Entry } ->
-            Vs = Vs0#{ Ref => Entry#value{type=Type} },
-            Vst#vst{current=St#st{vs=Vs}};
-        #{} ->
-            %% Dead references may happen during type inference and are not an
-            %% error in and of themselves. If a problem were to arise from this
-            %% it'll explode elsewhere.
-            Vst
-    end.
+    #{ Ref := #value{}=Entry } = Vs0,
+    Vs = Vs0#{ Ref => Entry#value{type=Type} },
+    Vst#vst{current=St#st{vs=Vs}}.
 
 new_value(Type, Op, Ss, #vst{current=#st{vs=Vs0}=St,ref_ctr=Counter}=Vst) ->
     Ref = #value_ref{id=Counter},