Handle terms in the top-level of guards properly

Expressions in guards such as:

f() when [1,2,3] ->
    ok.

would cause the debugger to crash when attempting to interpret the
module containing the expressions. Other kind of constants such as:

f() when 42 ->
    ok.

were converted to an invalid internal format ({integer,Line,42}
instead of {value,Line,42}), but that happened to work because
because anything not equal to 'true' (even a crash) was interpreted
as 'false'.

Make sure to handle all possible expressions and convert them
directly to {value,Line,false}. Remove the special handling of
the atom 'true' in and_guard/1 since it is no longer needed.

1 files changed, 12 insertions, 8 deletions

diff --git a/lib/debugger/src/dbg_iload.erl b/lib/debugger/src/dbg_iload.erl
index db0fe0bc10..acaf664fc6 100644
--- a/lib/debugger/src/dbg_iload.erl
+++ b/lib/debugger/src/dbg_iload.erl
@@ -225,8 +225,6 @@ guard([G0|Gs]) ->
     [G1|guard(Gs)];
 guard([]) -> [].
 
-and_guard([{atom,_,true}|Gs]) ->
-    and_guard(Gs);
 and_guard([G0|Gs]) ->
     G1 = guard_test(G0),
     [G1|and_guard(Gs)];
@@ -251,12 +249,18 @@ guard_test({op,Line,Op,L0,R0}) ->
     L1 = gexpr(L0),
     R1 = gexpr(R0),				%They see the same variables
     {safe_bif,Line,erlang,Op,[L1,R1]};
-guard_test({integer,_,_}=I) -> I;
-guard_test({char,_,_}=C) -> C;
-guard_test({float,_,_}=F) -> F;
-guard_test({atom,_,_}=A) -> A;
-guard_test({nil,_}=N) -> N;
-guard_test({var,_,_}=V) ->V.    % Boolean var
+guard_test({var,_,_}=V) ->V;    % Boolean var
+guard_test({atom,Line,true}) -> {value,Line,true};
+%% All other constants at this level means false.
+guard_test({atom,Line,_}) -> {value,Line,false};
+guard_test({integer,Line,_}) -> {value,Line,false};
+guard_test({char,Line,_}) -> {value,Line,false};
+guard_test({float,Line,_}) -> {value,Line,false};
+guard_test({string,Line,_}) -> {value,Line,false};
+guard_test({nil,Line}) -> {value,Line,false};
+guard_test({cons,Line,_,_}) -> {value,Line,false};
+guard_test({tuple,Line,_}) -> {value,Line,false};
+guard_test({bin,Line,_}) ->  {value,Line,false}.
 
 gexpr({var,Line,V}) -> {var,Line,V};
 gexpr({integer,Line,I}) -> {value,Line,I};