Re: meta-riscv: building curl, "undefined reference to '__atomic_exchange_1'


Khem Raj
 



On Thu, Jul 7, 2022 at 2:01 PM Robert P. J. Day <rpjday@...> wrote:
On Thu, 7 Jul 2022, Khem Raj wrote:

> On Thu, Jul 7, 2022 at 1:06 PM Robert P. J. Day <rpjday@...> wrote:
> >
> > On Thu, 7 Jul 2022, Khem Raj wrote:
> >
> > > On Thu, Jul 7, 2022 at 6:14 AM Robert P. J. Day <rpjday@...> wrote:
> > > >
> > > > On Thu, 7 Jul 2022, Robert P. J. Day wrote:
> > > >
> > > >
> > > > >   on admittedly unsupported ubuntu 22.04 platform but it's clear this
> > > > > is a known issue as it's pretty much identical to what one reads here:
> > > > >
> > > > >   https://github.com/advancedtelematic/aktualizr/issues/1427
> > > > >
> > > > > the explanation being that, "not every atomic operation is currently
> > > > > supported by GCC on RISC-V."
> > > > >
> > > > >   oddly, building a riscv64 core-image-minimal once upon a time on
> > > > > fedora worked just fine, so i'm assuming a difference in gcc versions
> > > > > is what is causing this.
> > > > >
> > > > >   what is the recommended workaround for this?
> > > >
> > > >   another data point, matches exactly what i'm referring to:
> > > >
> > > >   https://github.com/curl/curl/issues/9055
> > > >
> > >
> > > does backporting
> > >
> > > https://github.com/curl/curl/commit/50efb0822aa0e0ab165158dd0a26e65a2290e6d2
> > >
> > > to curl help ?
> >
> >   as i read it, this issue is also related to -pthread versus
> > -lpthread:
> >
>
> this would mean that you want to rely on side effects of -pthread
> which may work with gcc but may not
> work with clang or other compiler drivers. The issue you have is that
> some variables are needing atomics
> and solution is either you link with libatomic or avoid using the code
> which needs them
>
> > https://blog.jiejiss.com/A-RISC-V-gcc-pitfall-revealed-by-a-glibc-update/

  so while i'm still trying to wrap my head around all this, what
*would* be the ideal resolution for this? the link above suggests the
simple solution of introducing a gcc config option
"--always-link-libatomic". would that solve all this in a general way,
not just for RISC-V?

Probably, but again if you need a function from a library you include it on linker cmdline if it’s intrinsics then compiler driver doing the needed is best way 
Preferably without introducing compiler specific options 


rday

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