[fpc-pascal] ShortString still relevant today?

Hairy Pixels genericptr at gmail.com
Tue Jul 4 06:11:30 CEST 2023

> On Jul 4, 2023, at 10:11 AM, Nikolay Nikolov via fpc-pascal <fpc-pascal at lists.freepascal.org> wrote:
> ShortString is mainly for compatibility with Turbo Pascal, not for performance, IMHO. Although the FPC compiler itself still uses ShortString for performance reasons (I think the main advantage is the avoidance of the implicit try..finally blocks, needed for ansistrings). It might be interesting to benchmark the compiler with AnsiStrings instead of ShortStrings and see if there's a performance difference. But even if there is, a compiler is an extreme example. For 99% of the programs, performance impact of AnsiString is not an issue. I put {$H+} in almost all my new programs. I'd say that in 99% of the legit use cases, ShortString is used and needed for compatibility with legacy code, not for performance. Switching legacy code to {$H+} doesn't always work and may need additional fixes. Old code does things like S[0] := x instead of SetLength(S, x), etc. It also does uglier things, like FillChar() or Move() directly to/from string memory, or saves ShortStrings to files, as a part of a record, etc.

One thing I can think of now is that adding an AnsiString to a record or class makes that type "managed" and so it needs extra finalization when going out of scope. Static arrays will need to finalize their members too and the RTL has to do extra work in the lists classes to ensure this happens , which bloats the generic container types.

Ryan Joseph

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