Re: size_t and int64_t on a new platform

[Rich Felker <dalias@libc.org>]

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.

Anyone else have objections to use of long for these types?

Rich