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[3.7] bpo-36256: Fix bug in parsermodule when parsing if statements (GH-12477) #12488

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Merged
merged 1 commit into from
Mar 21, 2019
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[3.7] bpo-36256: Fix bug in parsermodule when parsing if statements (GH-12477) #12488

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4 changes: 4 additions & 0 deletions Lib/test/test_parser.py
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Original file line number Diff line number Diff line change
Expand Up @@ -318,6 +318,10 @@ def test_try_stmt(self):
self.check_suite("try: pass\nexcept: pass\nelse: pass\n"
"finally: pass\n")

def test_if_stmt(self):
self.check_suite("if True:\n pass\nelse:\n pass\n")
self.check_suite("if True:\n pass\nelif True:\n pass\nelse:\n pass\n")

def test_position(self):
# An absolutely minimal test of position information. Better
# tests would be a big project.
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2019-03-21-00-24-18.bpo-12477.OZHa0t.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix bug in parsermodule when parsing a state in a DFA that has two or more
arcs with labels of the same type. Patch by Pablo Galindo.
22 changes: 17 additions & 5 deletions Modules/parsermodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -666,7 +666,12 @@ validate_node(node *tree)
for (arc = 0; arc < dfa_state->s_narcs; ++arc) {
short a_label = dfa_state->s_arc[arc].a_lbl;
assert(a_label < _PyParser_Grammar.g_ll.ll_nlabels);
if (_PyParser_Grammar.g_ll.ll_label[a_label].lb_type == ch_type) {

const char *label_str = _PyParser_Grammar.g_ll.ll_label[a_label].lb_str;
if ((_PyParser_Grammar.g_ll.ll_label[a_label].lb_type == ch_type)
&& ((ch->n_str == NULL) || (label_str == NULL)
|| (strcmp(ch->n_str, label_str) == 0))
) {
/* The child is acceptable; if non-terminal, validate it recursively. */
if (ISNONTERMINAL(ch_type) && !validate_node(ch))
return 0;
Expand All @@ -679,17 +684,24 @@ validate_node(node *tree)
/* What would this state have accepted? */
{
short a_label = dfa_state->s_arc->a_lbl;
int next_type;
if (!a_label) /* Wouldn't accept any more children */
goto illegal_num_children;

next_type = _PyParser_Grammar.g_ll.ll_label[a_label].lb_type;
if (ISNONTERMINAL(next_type))
int next_type = _PyParser_Grammar.g_ll.ll_label[a_label].lb_type;
const char *expected_str = _PyParser_Grammar.g_ll.ll_label[a_label].lb_str;

if (ISNONTERMINAL(next_type)) {
PyErr_Format(parser_error, "Expected node type %d, got %d.",
next_type, ch_type);
else
}
else if (expected_str != NULL) {
PyErr_Format(parser_error, "Illegal terminal: expected '%s'.",
expected_str);
}
else {
PyErr_Format(parser_error, "Illegal terminal: expected %s.",
_PyParser_TokenNames[next_type]);
}
return 0;
}

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