Re: My review of Decimal

From: Ivan Matek (libbooze_at_[hidden])
Date: 2025-01-21 17:56:21

On Tue, Jan 21, 2025 at 6:06 PM Peter Dimov <pdimov_at_[hidden]> wrote:

> Basically, _fast types are almost never fast. Let's hope this curse doesn't
> afflict Decimal _fast types as well. :-)
>
> Thank you for confirming this, now I regret not writing that also in
review. :)

To recap the discussion wrt pass by reference:
points we agree on(wrt 64 bit x86):

   - if we pass by value on Windows we are out of luck for most decimal
   types since there is ABI limitation for types greater than 8 bytes
   - use of uint16_fast_t in  implementation pushed decimal64_fast over the
   limit of Linux ABI(16 bytes), _fast std:: types are not fast, would be nice
   to change this even if will not help on Windows

points we disagree on:

   - pass by reference for large types (and if necessary mutate inplace) is
   still my prefered API. If we do want value returning functions then for
   large types I would prefer to pass args by const reference.

Not trying to change your mind, just recapping above discussion, doing all
sizeof and ABI math is tricky.