Re: [PATCH v2 11/18] maintenance: auto-size incremental-repack batch

From: Chris Torek <chris.torek@gmail.com>
Date: Jul 30, 2020, 19:24 UTC
Message-ID: <CAPx1GvfcDeCBLMFbTtCpEK13uCWQQ+u=R1x1qE2kBD3eXVwh7A@mail.gmail.com>
In-Reply-To: <c0b9876a-9041-3400-25ac-e52568a02074@gmail.com>

On Thu, Jul 30, 2020 at 12:04 PM Derrick Stolee <stolee@gmail.com> wrote:

Show 7 quoted lines

> > This is actually ((1 << 31) - 1) because "unsigned long" is 32-bits
> > on Windows. But it's better to not use magic numbers and instead use
> > operations like this.
>
> Nevermind. This breaks the build on 32-bit machines (even adding a few
> "L" characters). I'll replace my magic decimal number with a magic
> hexadecimal number.

You would need something along these lines:

    #define WHATEVER ((long)((1UL << 31) - 1))

i.e., make the constant 1 be "unsigned long" so that the shift is well defined, then subtract 1, then convert back to signed long.

I say "something along" because there are several more ways to write it. I'm not really a big fan of most of them, and 0x7FFFFFFF (or in lowercase) is my own preference here too.

Chris