Re: [PATCH 0/1] MR1055: gdi32: Don't stackoverflow if substitute doesn't change anything

[Fabian Maurer (＠DarkShadow44)]

On Thu Oct 13 19:31:48 2022 +0000, Nikolay Sivov wrote:
> This does not lookup right. As I understand GSUB_E_NOGLYPH is used when
> lookup wasn't applied, but for example harfbuzz (and corresponding
> dwrite logic) does not check for zero delta, and lookup considered
> applied there.
> What exactly happens, and why zero delta is a problem?

GSUB_apply_feature_all_lookups calls itself infinitely, until stackoverflow.

As I understand it, it's supposed to apply lookups until none is left. But when we add 0 to a glyph, the lookup doesn't change anything, and we keep trying to apply the same lookup forever.

You can test with the program linked at https://bugs.winehq.org/show_bug.cgi?id=53787