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authorBjörn Gustavsson <[email protected]>2019-05-23 07:22:41 +0200
committerBjörn Gustavsson <[email protected]>2019-05-23 10:12:23 +0200
commit5959fb00182048d50f55d04684723d383d1aeee8 (patch)
treef01d55472255bf60398116eb719ede79dae4011c
parent7fe7fa3dde556b5b92522f8279d465bb52baf1f6 (diff)
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Fix sticky class in exception
When catching an exception re-throwing with a changed class, the class could be changed to the original class if the exception got caught and rethrown in (for example) an after block: sticky_class() -> try try throw(reason) catch throw:Reason:Stack -> erlang:raise(error, Reason, Stack) end after ok end.
-rw-r--r--erts/emulator/beam/beam_emu.c20
-rw-r--r--erts/emulator/beam/instrs.tab17
-rw-r--r--erts/emulator/test/exception_SUITE.erl34
3 files changed, 68 insertions, 3 deletions
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index 3af0838794..ec4f9b4339 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -422,6 +422,7 @@ static Eterm add_stacktrace(Process* c_p, Eterm Value, Eterm exc);
static void save_stacktrace(Process* c_p, BeamInstr* pc, Eterm* reg,
ErtsCodeMFA *bif_mfa, Eterm args);
static struct StackTrace * get_trace_from_exc(Eterm exc);
+static Eterm *get_freason_ptr_from_exc(Eterm exc);
static Eterm make_arglist(Process* c_p, Eterm* reg, int a);
void
@@ -1904,6 +1905,25 @@ static int is_raised_exc(Eterm exc) {
}
}
+static Eterm *get_freason_ptr_from_exc(Eterm exc) {
+ static Eterm dummy_freason;
+ struct StackTrace* s;
+
+ if (exc == NIL) {
+ /*
+ * Is is not exactly clear when exc can be NIL. Probably only
+ * when the exception has been generated from native code.
+ * Return a pointer to an Eterm that can be safely written and
+ * ignored.
+ */
+ return &dummy_freason;
+ } else {
+ ASSERT(is_list(exc));
+ s = (struct StackTrace *) big_val(CDR(list_val(exc)));
+ return &s->freason;
+ }
+}
+
/*
* Creating a list with the argument registers
*/
diff --git a/erts/emulator/beam/instrs.tab b/erts/emulator/beam/instrs.tab
index 42c1168f85..999e9337ff 100644
--- a/erts/emulator/beam/instrs.tab
+++ b/erts/emulator/beam/instrs.tab
@@ -951,19 +951,30 @@ raw_raise() {
Eterm class = x(0);
Eterm value = x(1);
Eterm stacktrace = x(2);
+ Eterm* freason_ptr;
+
+ /*
+ * Note that the i_raise instruction will override c_p->freason
+ * with the freason field stored inside the StackTrace struct in
+ * ftrace. Therefore, we must take care to store the class both
+ * inside the StackTrace struct and in c_p->freason (important if
+ * the class is different from the class of the original
+ * exception).
+ */
+ freason_ptr = get_freason_ptr_from_exc(stacktrace);
if (class == am_error) {
- c_p->freason = EXC_ERROR & ~EXF_SAVETRACE;
+ *freason_ptr = c_p->freason = EXC_ERROR & ~EXF_SAVETRACE;
c_p->fvalue = value;
c_p->ftrace = stacktrace;
goto find_func_info;
} else if (class == am_exit) {
- c_p->freason = EXC_EXIT & ~EXF_SAVETRACE;
+ *freason_ptr = c_p->freason = EXC_EXIT & ~EXF_SAVETRACE;
c_p->fvalue = value;
c_p->ftrace = stacktrace;
goto find_func_info;
} else if (class == am_throw) {
- c_p->freason = EXC_THROWN & ~EXF_SAVETRACE;
+ *freason_ptr = c_p->freason = EXC_THROWN & ~EXF_SAVETRACE;
c_p->fvalue = value;
c_p->ftrace = stacktrace;
goto find_func_info;
diff --git a/erts/emulator/test/exception_SUITE.erl b/erts/emulator/test/exception_SUITE.erl
index aec66cb9a3..6e6f7d78ab 100644
--- a/erts/emulator/test/exception_SUITE.erl
+++ b/erts/emulator/test/exception_SUITE.erl
@@ -23,6 +23,7 @@
-export([all/0, suite/0,
badmatch/1, pending_errors/1, nil_arith/1, top_of_stacktrace/1,
stacktrace/1, nested_stacktrace/1, raise/1, gunilla/1, per/1,
+ change_exception_class/1,
exception_with_heap_frag/1, backtrace_depth/1,
line_numbers/1]).
@@ -43,6 +44,7 @@ suite() ->
all() ->
[badmatch, pending_errors, nil_arith, top_of_stacktrace,
stacktrace, nested_stacktrace, raise, gunilla, per,
+ change_exception_class,
exception_with_heap_frag, backtrace_depth, line_numbers].
-define(try_match(E),
@@ -507,6 +509,38 @@ t1(_,X,_) ->
t2(_,X,_) ->
(X bsl 1) + 1.
+change_exception_class(_Config) ->
+ try
+ change_exception_class_1(fun() -> throw(arne) end)
+ catch
+ error:arne ->
+ ok;
+ Class:arne ->
+ ct:fail({wrong_exception_class,Class})
+ end.
+
+change_exception_class_1(F) ->
+ try
+ change_exception_class_2(F)
+ after
+ %% The exception would be caught and rethrown using
+ %% an i_raise instruction. Before the correction
+ %% of the raw_raise instruction, the change of class
+ %% would not stick.
+ io:put_chars("Exception automatically rethrown here\n")
+ end.
+
+change_exception_class_2(F) ->
+ try
+ F()
+ catch
+ throw:Reason:Stack ->
+ %% Translated to a raw_raise instruction.
+ %% The change of exception class would not stick
+ %% if the i_raise instruction was later executed.
+ erlang:raise(error, Reason, Stack)
+ end.
+
%%
%% Make sure that even if a BIF builds an heap fragment, then causes an exception,
%% the stacktrace term will still be OK (specifically, that it does not contain