Re: [PATCH] RISC-V: Fix elfutils testsuite unwind failures.

[DJ Delorie <dj at redhat dot com>]

I'm OK with this patch plus or minus the return from main comment I
added below.  If someone "in the know" can comment on that comment, I
can commit the patch once we have consensus on it.

Jim Wilson <jimw@sifive.com> writes:
> -CFLAGS-tst-unwind-main.c += -funwind-tables
> +CFLAGS-tst-unwind-main.c += -funwind-tables -DUSE_PTHREADS=0

This allows for the test to run the "old" way, ok.

>  static _Unwind_Reason_Code
>  callback (struct _Unwind_Context *ctx, void *arg)
>  {
>    return _URC_NO_REASON;
>  }
>  
> -int
> -main (void)
> +static void *
> +func (void *a)
>  {
>    /* Arrange for this test to be killed if _Unwind_Backtrace runs into an
>       endless loop.  We cannot use the test driver because the complete
>       call chain needs to be compiled with -funwind-tables so that
> -     _Unwind_Backtrace is able to reach _start.  */
> +     _Unwind_Backtrace is able to reach the start routine.  */
>    alarm (DEFAULT_TIMEOUT);
>    _Unwind_Backtrace (callback, 0);
> +  return a;
> +}
> +
> +int
> +main (void)
> +{
> +#if USE_PTHREADS
> +  pthread_t thr;
> +  int rc = pthread_create (&thr, NULL, &func, NULL);
> +  if (rc)
> +    error (1, rc, "pthread_create");
> +  rc = pthread_join (thr, NULL);
> +  if (rc)
> +    error (1, rc, "pthread_join");
> +#else
> +  func (NULL);
> +#endif
>  }

main() should return something in the fall-through case, be it zero
(main should exit) or 1 (code shouldn't be reached), now that main()
doesn't end with _Unwind_Backtrace() itself, if for no reason than to
avoid future warnings.

> -	tst-rwlock-pwn
> +	tst-rwlock-pwn tst-unwind-thread

ok

> +CFLAGS-tst-unwind-thread.c += -funwind-tables

ok, same as original test.

> +#define USE_PTHREADS 1
> +#include "../elf/tst-unwind-main.c"

Ok.

>  ENTRY (__thread_start)
>  L (thread_start):
> +	/* Terminate call stack by noting ra is undefined.  Use a dummy
> +	   .cfi_label to force starting the FDE.  */
> +	.cfi_label .Ldummy
> +	cfi_undefined (ra)
> +

As noted, this matches start.S, so ok.