Fix coverage measurement for negative line numbers

Fixes [Bug #21220]

Co-Authored-By: Mike Bourgeous <mike@mikebourgeous.com>
Co-Authored-By: Jean Boussier <jean.boussier@gmail.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/thread.c b/thread.c
index 661ee977a9..b7aa911620 100644
--- a/thread.c
+++ b/thread.c
@@ -5662,6 +5662,7 @@ update_line_coverage(VALUE data, const rb_trace_arg_t *trace_arg)
         VALUE lines = RARRAY_AREF(coverage, COVERAGE_INDEX_LINES);
         if (lines) {
             long line = rb_sourceline() - 1;
+            VM_ASSERT(line >= 0);
             long count;
             VALUE num;
             void rb_iseq_clear_event_flags(const rb_iseq_t *iseq, size_t pos, rb_event_flag_t reset);