[Buildroot] [PATCH 1/1] package/capnproto: fix build on riscv32

[Fabrice Fontaine]

Hi Arnout,

Le ven. 28 mai 2021 à 16:17, Arnout Vandecappelle <arnout at mind.be> a écrit :
>
>
>
> On 28/05/2021 09:11, Fabrice Fontaine wrote:
> > Hi Koen,
> >
> > Le ven. 28 mai 2021 à 09:00, Koen Martens <gmc at sonologic.nl> a écrit :
> >>
> >> Hi,
> >>
> >> Thanks for diving into this. I've had emails about this for months, and briefly
> >> looked at it, but never found the time to properly figure it out.
> >>
> >> I see the patch below is also present upstream. Do you know whether this has
> >> already been released or when it will be?
> > I don't know when upstream will release a new version.
> > However, after digging through a lot of riscv32 build failures on
> > other packages, I'm not sure that this upstream patch is right
> > anymore.
> > Aliasing SYS_futex to SYS_futex_time64 has been rejected by vlc for example:
> > https://patches.videolan.org/patch/30581/
>
>  That patch looks OK to me:
>
> +/* 32bit architectures with 64bit time_t do not define __NR_futex syscall */
> +#if !defined(SYS_futex) && defined(SYS_futex_time64)
> +#define SYS_futex SYS_futex_time64
> +#endif
>
>  The comment was "this patch won't work if the userspace ABI uses the
> 64-bit time_t on a 32-bit ISA that did start with 32-bit time_t" - but that's
> not true. On a 32-bit ISA that did start with 32-bit time_t, SYS_futex will be
> defined (or SYS_foo is not properly exported by libc and then SYS_futex_time64
> isn't defined either).
>
>  To be really safe, you should maybe also check that __TIMESIZE == 64 [1] - but
> that may break on musl or uClibc.
>
>  Or even better of course would be to patch all code to use the __time64_t
> instead of time_t everywhere, independent of __TIMESIZE. But even then you'd
> need fallback to time_t for old libc/kernel.
Thanks for your feedback, I'll then send a v2 of my patch for vlc to
fix the build on riscv32 instead of disabling it.
>
>
>  Regards,
>  Arnout
>
>
> [1]
> https://www.gnu.org/software/libc/manual/html_node/64_002dbit-time-symbol-handling.html
>
>
>
>
>
> > So another option would be to just disable capnproto on riscv32.
> >>
> >> Given that this exact patch is also applied upstream, your patch below seems fine
> >> to me.
> >>
> >> Cheers,
> >>
> >> Koen
> >>
> >> On Thu, May 27, 2021 at 11:04:02PM +0200, Fabrice Fontaine wrote:
> >>> Fixes:
> >>>  - http://autobuild.buildroot.org/results/1c1cd4775241ee57d878cad5c978413d4b4a8736
> >>>
> >>> Signed-off-by: Fabrice Fontaine <fontaine.fabrice at gmail.com>
> >>> ---
> >>>  ...it-architectures-using-64-bit-time_t.patch | 37 +++++++++++++++++++
> >>>  1 file changed, 37 insertions(+)
> >>>  create mode 100644 package/capnproto/0001-mutex-Fix-build-on-32-bit-architectures-using-64-bit-time_t.patch
> >>>
> >>> diff --git a/package/capnproto/0001-mutex-Fix-build-on-32-bit-architectures-using-64-bit-time_t.patch b/package/capnproto/0001-mutex-Fix-build-on-32-bit-architectures-using-64-bit-time_t.patch
> >>> new file mode 100644
> >>> index 0000000000..ce70ab8f29
> >>> --- /dev/null
> >>> +++ b/package/capnproto/0001-mutex-Fix-build-on-32-bit-architectures-using-64-bit-time_t.patch
> >>> @@ -0,0 +1,37 @@
> >>> +From e2a05a19e9dc51287e19cc9f11fd91449219e361 Mon Sep 17 00:00:00 2001
> >>> +From: Khem Raj <raj.khem at gmail.com>
> >>> +Date: Sun, 15 Nov 2020 12:10:28 -0800
> >>> +Subject: [PATCH] mutex: Fix build on 32-bit architectures using 64-bit time_t
> >>> +
> >>> +mutex code uses SYS_futex, which it expects from system C library.
> >>> +in glibc (/usr/include/bits/syscall.h defines it in terms of of NR_futex)
> >>> +rv32 is using 64bit time_t from get go unlike other 32bit architectures
> >>> +in glibc, therefore it wont have NR_futex defined but just NR_futex_time64
> >>> +this aliases it to NR_futex so that SYS_futex is then defined for rv32
> >>> +
> >>> +Signed-off-by: Khem Raj <raj.khem at gmail.com>
> >>> +[Retrieved from:
> >>> +https://github.com/capnproto/capnproto/commit/e2a05a19e9dc51287e19cc9f11fd91449219e361]
> >>> +Signed-off-by: Fabrice Fontaine <fontaine.fabrice at gmail.com>
> >>> +---
> >>> + c++/src/kj/mutex.c++ | 6 ++++++
> >>> + 1 file changed, 6 insertions(+)
> >>> +
> >>> +diff --git a/c++/src/kj/mutex.c++ b/c++/src/kj/mutex.c++
> >>> +index c81cead7b..e1594b117 100644
> >>> +--- a/c++/src/kj/mutex.c++
> >>> ++++ b/c++/src/kj/mutex.c++
> >>> +@@ -39,7 +39,13 @@
> >>> +
> >>> + #ifndef SYS_futex
> >>> + // Missing on Android/Bionic.
> >>> ++#ifdef __NR_futex
> >>> + #define SYS_futex __NR_futex
> >>> ++#elif defined(SYS_futex_time64)
> >>> ++#define SYS_futex SYS_futex_time64
> >>> ++#else
> >>> ++#error "Need working SYS_futex"
> >>> ++#endif
> >>> + #endif
> >>> +
> >>> + #ifndef FUTEX_WAIT_PRIVATE
> >>> --
> >>> 2.30.2
> >>>
> > Best Regards,
> >
> > Fabrice
> > _______________________________________________
> > buildroot mailing list
> > buildroot at busybox.net
> > http://lists.busybox.net/mailman/listinfo/buildroot
> >
Best Regards,

Fabrice