stdlib: Add check of stacktrace variable to erl_eval

Some of the functions of the erl_eval module do not call the Erlang
code linter, so they need to explicitly check that the newly
introduced stacktrace variable is not bound.

2 files changed, 39 insertions, 3 deletions

diff --git a/lib/stdlib/src/erl_eval.erl b/lib/stdlib/src/erl_eval.erl
index 489f65290a..4ee11383da 100644
--- a/lib/stdlib/src/erl_eval.erl
+++ b/lib/stdlib/src/erl_eval.erl
@@ -904,9 +904,9 @@ if_clauses([], _Bs, _Lf, _Ef, _RBs) ->
 
 %% try_clauses(Body, CaseClauses, CatchClauses, AfterBody, Bindings, 
 %%             LocalFuncHandler, ExtFuncHandler, RBs)
-%% When/if variable bindings between the different parts of a
-%% try-catch expression are introduced this will have to be rewritten.
+
 try_clauses(B, Cases, Catches, AB, Bs, Lf, Ef, RBs) ->
+    check_stacktrace_vars(Catches, Bs),
     try exprs(B, Bs, Lf, Ef, none) of
 	{value,V,Bs1} when Cases =:= [] ->
 	    ret_expr(V, Bs1, RBs);
@@ -919,7 +919,6 @@ try_clauses(B, Cases, Catches, AB, Bs, Lf, Ef, RBs) ->
 	    end
     catch
 	Class:Reason:Stacktrace when Catches =:= [] ->
-	    %% Rethrow
 	    erlang:raise(Class, Reason, Stacktrace);
 	Class:Reason:Stacktrace ->
             V = {Class,Reason,Stacktrace},
@@ -937,6 +936,23 @@ try_clauses(B, Cases, Catches, AB, Bs, Lf, Ef, RBs) ->
 	end
     end.
 
+check_stacktrace_vars([{clause,_,[{tuple,_,[_,_,STV]}],_,_}|Cs], Bs) ->
+    case STV of
+        {var,_,V} ->
+            case binding(V, Bs) of
+                {value, _} ->
+                    erlang:raise(error, stacktrace_bound, ?STACKTRACE);
+                unbound ->
+                    check_stacktrace_vars(Cs, Bs)
+            end;
+        _ ->
+            erlang:raise(error,
+                         {illegal_stacktrace_variable,STV},
+                         ?STACKTRACE)
+    end;
+check_stacktrace_vars([], _Bs) ->
+    ok.
+
 %% case_clauses(Value, Clauses, Bindings, LocalFuncHandler, ExtFuncHandler, 
 %%              RBs)
 
diff --git a/lib/stdlib/test/erl_eval_SUITE.erl b/lib/stdlib/test/erl_eval_SUITE.erl
index 3c95b5781e..8eb85cab8e 100644
--- a/lib/stdlib/test/erl_eval_SUITE.erl
+++ b/lib/stdlib/test/erl_eval_SUITE.erl
@@ -1033,6 +1033,14 @@ otp_14826(_Config) ->
     backtrace_check("try a of b -> bar after foo end.",
                     {try_clause,a},
                     [{erl_eval,try_clauses,8}]),
+    check(fun() -> X = try foo:bar() catch A:B:C -> {A,B} end, X end,
+          "try foo:bar() catch A:B:C -> {A,B} end.",
+          {error, undef}),
+    backtrace_check("C = 4, try foo:bar() catch A:B:C -> {A,B,C} end.",
+                    stacktrace_bound,
+                    [{erl_eval,check_stacktrace_vars,2},
+                     {erl_eval,try_clauses,8}],
+                    none, none),
     backtrace_catch("catch (try a of b -> bar after foo end).",
                     {try_clause,a},
                     [{erl_eval,try_clauses,8}]),
@@ -1040,6 +1048,18 @@ otp_14826(_Config) ->
                     badarith,
                     [{erlang,'/',[1,0],[]},
                      {erl_eval,do_apply,6}]),
+    Es = [{'try',1,[{call,1,{remote,1,{atom,1,foo},{atom,1,bar}},[]}],
+           [],
+           [{clause,1,[{tuple,1,[{var,1,'A'},{var,1,'B'},{atom,1,'C'}]}],
+             [],[{tuple,1,[{var,1,'A'},{var,1,'B'},{atom,1,'C'}]}]}],[]}],
+    try
+        erl_eval:exprs(Es, [], none, none),
+        ct:fail(stacktrace_variable)
+    catch
+        error:{illegal_stacktrace_variable,{atom,1,'C'}}:S ->
+            [{erl_eval,check_stacktrace_vars,2,_},
+             {erl_eval,try_clauses,8,_}|_] = S
+    end,
     backtrace_check("{1,1} = {A = 1, A = 2}.",
                     {badmatch, 1},
                     [erl_eval, {lists,foldl,3}]),