what is the possible reason of IOS8 whatsapp would crash if db contain duo-letters “ff”, “fi” or “tt”

Question

Just curious, why storing "ff","fi","tt" these duo letters would cause the crash on whatsapp?? anyone could give a possible reason?

more details here WhatsApp Crashing fix method

Answer 1

Those are ligatures, character sequences that are often combined into a single glyph for output.

For the ff and fi ones, some typefaces have the hood of the f impinging into the space of the next character, meaning they're better treated as a single printable unit. The fi is an extreme case as the hood of the f often often joins up with the tittle (dot) of the i.

The reason for the fault is possibly a disagreement somewhere between the data stored by WhatsApp and the data rendered by the control. Without having the source code to WhatsApp, it's rather hard to be sure.

It may also be the actual data stored within the database (or any conversion as it's extracted from the database). If the Unicode code points for the ligature itself are being stored (or presented on extraction), that may confuse WhatsApp when it comes time to use it. Example is the Latin Small Ligature ff, a single code point U+FB00.

This seems more likely to me than the first case since a common fix is to go through the database, changing ff sequences into f f (with an intervening space) - that seems to negate the possibility that the ligature code point itself is being stored.

However, why it happens is almost certainly moot. WhatsApp should be fixing the problem, plain and simple.