Re: [RFC v6 07/23] RISC-V: Use 64-bit time_t and off_t for RV32 and RV64

[Joseph Myers <joseph at codesourcery dot com>]

On Tue, 11 Feb 2020, Alistair Francis wrote:

> > > diff --git a/sysdeps/unix/sysv/linux/riscv/bits/typesizes.h b/sysdeps/unix/sysv/linux/riscv/bits/typesizes.h
> > > new file mode 100644
> > > index 0000000000..0da3bdeb5d
> > > --- /dev/null
> > > +++ b/sysdeps/unix/sysv/linux/riscv/bits/typesizes.h
> >
> > I was hoping newer arches could simply use the asm-generic one ?
> 
> We need to specify that RV32 uses a 64-bit time_t. The generic ones
> don't do that for 32-bit arches.

Since it seems we'd like future 32-bit ports of glibc to use 64-bit time 
and offsets, we should make that as easy as possible.

That is, you need an RISC-V-specific bits/timesize.h.  But you shouldn't 
need an RISC-V-specific bits/typesizes.h - rather, make the linux/generic 
one do the right thing for __TIME_T_TYPE based on bits/timesize.h.  And 
have some other header that 32-bit linux/generic ports can use to say 
whether they use the 64-bit offset/stat/statfs interface, that 
bits/typesizes.h can use together with its existing __LP64__ check, and 
make the definitions of __OFF_T_TYPE etc. check that as well, and then you 
shouldn't need an RISC-V-specific bits/typesizes.h - the RISC-V-specific 
headers should be strictly minimal.  (No architecture-specific 
bits/time64.h headers should be needed in any case.)

At some point (or indeed now) we might flip the default for linux/generic 
so the architectures needing an architecture-specific header are only the 
older 32-bit linux/generic architectures that have support for 32-bit 
times and offsets, and the newer ones with no such support don't need such 
a header.

-- 
Joseph S. Myers
joseph@codesourcery.com