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Message-ID: <CACcSVPGh0pL2b1LZAuB-u+87yCrKTLcsVDYvS5z1bSN+ga=TCw@mail.gmail.com>
Date: Thu, 31 Mar 2016 17:35:11 -0700
From: Dan Gohman <sunfish@...illa.com>
To: musl@...ts.openwall.com
Subject: Re: size_t and int64_t on a new platform
On Thu, Mar 31, 2016 at 12:25 PM, Rich Felker <dalias@...c.org> wrote:
> On Thu, Mar 31, 2016 at 11:20:22AM -0700, Dan Gohman wrote:
> > I'm working on a new architecture (WebAssembly, aka wasm) and am hoping
> to
> > have a compatible ABI at the level of a "freestanding implementation"
> > between all libc ports.
> >
> > The current design would translate into the following in a musl port (in
> > ..../bits/alltypes.h.in):
> >
> > #define _Addr long
> > #define _Int64 long long
> >
> > Both the ILP32 and LP64 platform variants would use the same definitions.
> > This helps minimize differences between the two variants, which aligns
> with
> > an overall goal of the platform.
> >
> > However, this differs from musl's convention of using "int" for _Addr on
> > ILP32 systems and using "long" for _Int64 on LP64 systems. But, as far
> as I
> > can tell, no musl code actually depends on this convention. Almost all
> code
> > in musl is either fully portable and can't, or is architecture-specific
> and
> > can just do the right thing for its own architecture.
> >
> > Legacy code may have assumptions, though I'm aware of the issues and
> don't
> > believe it's a significant practical problem for WebAssembly.
> >
> > If we decide to contribute wasm support upstream to the musl project in
> the
> > future, would the musl maintainers expect to be ok with the above
> > definitions?
>
> At some point we'll probably have to make this relaxation anyway. I've
> heard there's at least one arch we're planning to add (maybe
> powerpc64? I forget) that's using long instead of int for _Addr types.
> What would be most helpful to us (to keep things simple) is just
> ensuring that all the relevant types (size_t, ssize_t, ptrdiff_t,
> [u]intptr_t, etc.) are defined consistently as int or as long;
> otherwise we have to pop a hole in the abstraction they're modeled
> with now. That wouldn't be a huge problem either but it just adds more
> redundancy to arch/*/bits/alltypes.h.in files.
>
Sounds good. And I agree; size_t, ssize_t, ptrdiff_t, [u]intptr_t, etc.
would all remain consistent with each other.
And to answer the concerns about compilers, I'm also a developer on the
first C/C++ compiler being ported to this platform, so I'll make sure that
the compiler's types agree with those defined in the library headers.
Thanks,
Dan
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