[Bug sanitizer/80308] asan crash on big-endian powerpc-linux target

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80308

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2017-04-04
     Ever confirmed|0                           |1

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Bernd Edlinger from comment #6)
> this looks suspicious:
> 
> --- asan.c.jj   2017-03-27 10:25:01.000000000 +0200
> +++ asan.c      2017-04-04 21:15:31.444941816 +0200
> @@ -2762,7 +2762,8 @@ asan_store_shadow_bytes (gimple_stmt_ite
>        unsigned char shadow_c = c;
>        if (i == size - 1 && last_chunk_size && !is_clobber)
>         shadow_c = last_chunk_size;
> -      val |= (unsigned HOST_WIDE_INT) shadow_c << (BITS_PER_UNIT * i);
> +      val |= (unsigned HOST_WIDE_INT) shadow_c
> +            << (BITS_PER_UNIT * (BYTES_BIG_ENDIAN ? size - 1 - i : i));
>      }
> 
>    /* Handle last chunk in unpoisoning.  */

Indeed, though perhaps it might be more readable to:
  for (unsigned i = 0; i < size; ++i)
    {
      unsigned char shadow_c = c;
      if (i == (BYTES_BIG_ENDIAN ? 0 : size - 1)
          && last_chunk_size
          && !is_clobber)
        shadow_c = last_chunk_size;
      val |= (unsigned HOST_WIDE_INT) shadow_c << (BITS_PER_UNIT * i);
    }

But we really want a testcase for the testsuite here.
It needs to be something simple that with (the default
-fsanitize-use-after-scope) unpoisons and later poisons a variable with size
that is not a multiple of 32 bytes, such as that size of 12.