A hostile file could abort any process that opens it: a cell formula of a
million `%` (`1%%%…`) or a 200,000-term sum parsed into trees deep enough to
overflow the stack when printed, saved, evaluated or dropped, even in release
builds. Postfix operators (`%`, invoking a result) built their nesting in a
loop that the 256-level limit did not see.
- `parse` refuses formula text longer than Excel's 8,192 characters
(`MAX_FORMULA_LEN`, counted in characters, the leading `=` excluded). This
also bounds the depth of the left-deep trees long operator chains build.
- Each postfix `%` and each call of a result counts towards the nesting limit.
- A file's formula that is refused keeps its text and cached value, as other
unparsable formulas do.
Regression tests: formula (small-stack thread: long `%`, invoke and operator
chains are errors; the limit counts characters, not bytes) and xlsx
(`hostile_formula_text_does_not_overflow_the_stack`: open, save and drop a
workbook with such formulas and a defined name on a 1 MiB stack). Both abort
with a stack overflow without the fix.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
A formula read with `cm` (Excel's XLDAPR dynamic-array record in
xl/metadata.xml) now carries `Formula::dynamic`, and the writer keeps the
`cm` and the metadata part for it even when the formula returns one value
and the export shape analysis would not need array evaluation. Before, such
formulas were saved as legacy formulas, so Excel recalculated some of them
with implicit intersection (SUMPRODUCT(IFERROR(range/range,0)) changed
value), and workbooks whose every dynamic formula was scalar lost
xl/metadata.xml altogether.
The mark survives moves, row and column insertion or deletion, sheet and
name renames and LAMBDA call-case fixes; retyping a formula drops it and
the writer decides from the formula's shape, as before. It is serialized
only when set, so saved documents without it are unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Brings the branch up to upstream's main (59 more commits). One conflict:
- docs/ui-parity.md: every line of both sides is kept, as upstream's own
merges keep them, in the order of their dates, newest first (upstream
has a change of the 13th now, which goes above this one of the 12th).
Gate: all eight steps, 1580 tests.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
