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fix(terminal): avoid integer overflow in selectPrev with no active matches (#12936)
Also found when test searching.
Run Ghostty debug on macOS and follow these steps:
1. Open Ghostty, `cat src/Surface.zig` and start search
`self.startClipboardRequest`.
2. Click up button(Press enter) 6 times and click down button (Press
shift+enter) 6 times.
3. You should see a panic crash.
### AI Disclosure
Claude implemented the fix and the unit test.
I reviewed it and tested it myself.
author
Mitchell Hashimoto
committer
GitHub
date
(Jun 5, 2026, 3:10 PM -0700)
commit
ea37f467
ea37f4672c84e749f56600a53d444b2ca4b0c903
parent
5a1edfb2
5a1edfb25402f06bc11568de3fcbf4bcc4b898be
+67
-1
+67
-1
src/terminal/search/screen.zig
+67
-1
src/terminal/search/screen.zig
···
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const active_len = self.active_results.items.len;
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const history_len = self.history_results.items.len;
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const next_idx = if (prev.idx != 0) prev.idx - 1 else active_len - 1 + history_len;
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const next_idx = if (prev.idx != 0) prev.idx - 1 else active_len + history_len - 1;
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const hl: FlattenedHighlight = if (next_idx < active_len)
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self.active_results.items[active_len - 1 - next_idx]
···
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.y = 1,
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} }, t.screens.active.pages.pointFromPin(.active, sel.end).?);
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}
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}
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test "select prev wraps when all matches are in history" {
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// Regression test: when every match is in scrollback (the active area
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// has none, so active_len == 0), selecting prev from index 0 must wrap
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// to the last result without underflowing `active_len - 1`.
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const alloc = testing.allocator;
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var t: Terminal = try .init(alloc, .{
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.cols = 10,
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.rows = 2,
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.max_scrollback = std.math.maxInt(usize),
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});
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defer t.deinit(alloc);
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const list: *PageList = &t.screens.active.pages;
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var s = t.vtStream();
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defer s.deinit();
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// Put the only match in scrollback, then scroll the active area to all
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// blank lines so it contains no match (active_len == 0, history_len == 1).
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s.nextSlice("Fizz\r\n");
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while (list.totalPages() < 3) s.nextSlice("\r\n");
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for (0..list.rows) |_| s.nextSlice("\r\n");
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var search: ScreenSearch = try .init(alloc, t.screens.active, "Fizz");
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defer search.deinit();
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try search.searchAll();
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try testing.expectEqual(0, search.active_results.items.len);
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// Select the first match (idx 0), then wrap backwards. This must not
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// panic and must keep a valid selection.
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_ = try search.select(.next);
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_ = try search.select(.prev);
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try testing.expect(search.selectedMatch() != null);
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}
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test "select after all matches disappear drops the selection" {
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// The wrap arithmetic in selectPrev (active_len + history_len - 1) would
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// underflow if a selection were ever live while both result lists are
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// empty. This guards the invariant that makes that unreachable: when a
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// reload/prune empties the results, the selection is dropped, so the next
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// select() hits the "no matches" guard instead of the wrap arithmetic.
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const alloc = testing.allocator;
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var t: Terminal = try .init(alloc, .{ .cols = 10, .rows = 2 });
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defer t.deinit(alloc);
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var s = t.vtStream();
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defer s.deinit();
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s.nextSlice("Fizz");
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var search: ScreenSearch = try .init(alloc, t.screens.active, "Fizz");
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defer search.deinit();
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try search.searchAll();
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try testing.expectEqual(1, search.active_results.items.len);
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// Take a selection, then overwrite the only match so a reload finds none
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// (active and history both empty).
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_ = try search.select(.next);
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try testing.expect(search.selectedMatch() != null);
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s.nextSlice("\x1b[1;1H ");
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// Must not underflow; the selection is dropped and nothing is selected.
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_ = try search.select(.prev);
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try testing.expect(search.selectedMatch() == null);
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try testing.expectEqual(0, search.active_results.items.len);
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try testing.expectEqual(0, search.history_results.items.len);
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}
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test "screen search no scrollback has no history" {