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Always enforce stack version limit during reductions

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Fixes #669
This commit is contained in:
Max Brunsfeld 2020-07-06 15:56:21 -07:00
parent 0438ed03ff
commit 0bf2450b4a
3 changed files with 28 additions and 6 deletions
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18
lib/src/parser.c
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@ -764,17 +764,23 @@ static StackVersion ts_parser__reduce(
bool is_extra
) {
uint32_t initial_version_count = ts_stack_version_count(self->stack);
uint32_t removed_version_count = 0;
StackSliceArray pop = ts_stack_pop_count(self->stack, version, count);
// Pop the given number of nodes from the given version of the parse stack.
// If stack versions have previously merged, then there may be more than one
// path back through the stack. For each path, create a new parent node to
// contain the popped children, and push it onto the stack in place of the
// children.
StackSliceArray pop = ts_stack_pop_count(self->stack, version, count);
uint32_t removed_version_count = 0;
for (uint32_t i = 0; i < pop.size; i++) {
StackSlice slice = pop.contents[i];
StackVersion slice_version = slice.version - removed_version_count;
// Error recovery can sometimes cause lots of stack versions to merge,
// such that a single pop operation can produce a lots of slices.
// Avoid creating too many stack versions in that situation.
if (i > 0 && slice_version > MAX_VERSION_COUNT + MAX_VERSION_COUNT_OVERFLOW) {
// This is where new versions are added to the parse stack. The versions
// will all be sorted and truncated at the end of the outer parsing loop.
// Allow the maximum version count to be temporarily exceeded, but only
// by a limited threshold.
if (slice_version > MAX_VERSION_COUNT + MAX_VERSION_COUNT_OVERFLOW) {
ts_stack_remove_version(self->stack, slice_version);
ts_subtree_array_delete(&self->tree_pool, &slice.subtrees);
removed_version_count++;