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Message-ID: <20160126202559.GM9621@port70.net>
Date: Tue, 26 Jan 2016 21:26:00 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: Bits deduplication: current situation
* Dan Gohman <sunfish@...illa.com> [2016-01-26 07:16:08 -0800]:
> On Tue, Jan 26, 2016 at 2:18 AM, Szabolcs Nagy <nsz@...t70.net> wrote:
> > * Dan Gohman <sunfish@...illa.com> [2016-01-25 21:03:54 -0800]:
> > > On Mon, Jan 25, 2016 at 1:32 PM, Szabolcs Nagy <nsz@...t70.net> wrote:
> > > > * Rich Felker <dalias@...c.org> [2016-01-25 16:00:05 -0500]:
> > > > >
> > > > > I'm pretty sure int64_t is long on all LP64 targets we support. Are
> > > > > there others that differ?
> > > >
> > >
> > > I'm working on an architecture which does, though there's no musl support
> > > for it currently.
> > >
> >
> > in gcc stdint.h only depends on libc/os and sizeof(long),
> > not on architecture.
> >
> > (e.g. openbsd uses long long, glibc uses long consistently
> > for all LP64 arch abis.)
> >
>
> I've been assuming that, in the absence of compatibility constraints (for
> example on a new architecture), it would be reasonable for hypothetical new
> musl, glibc, or newlib ports to arrange to be ABI compatible at the level
> of a freestanding implementation (in the C standard sense), which would
> include <stdint.h>. Is this an incorrect assumption, from your perspective?
it is correct in principle, but it means a bit more toolchain
work to support an inconsistent arch and it can bite you if
you work with historical code with invalid assumptions.
gcc/musl/glibc/linux all use consistent typedefs for all
64bit archs, most likely other projects do the same.
in most cases it should be easy to do the typedefs
differently for a new arch, but there might be caveats..
i think if you want to design a freestanding c language abi
for your arch then it makes sense to follow what's already
there (unless you have some specific reason to deviate).
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