Re: [PATCH] Big-endian targets: Fix implptrpiece.exp

[Yao Qi <qiyaoltc at gmail dot com>]

Hi Andreas,
Sorry for the delayed review.  I read this patch at least twice in the last
month, but didn't review because I can't understand it fully, and was
interrupted to do something else.

On Thu, Jan 19, 2017 at 12:52 PM, Andreas Arnez
<arnez@linux.vnet.ibm.com> wrote:
> The test case implptrpiece.exp accesses the second byte of the short
> integer number 1 and expects it to be zero.  This is valid for
> little-endian targets, but fails on big-endian targets.
>
> This is fixed by determining the expected value in an
> endianness-independent way.

This is quite clever, but I don't like it, :) because every time I read it,
it takes me a while what is the test trying to do.

>
> gdb/testsuite/ChangeLog:
>
>         * gdb.dwarf2/implptrpiece.exp: Fix check for big-endian targets.
> ---
>  gdb/testsuite/gdb.dwarf2/implptrpiece.exp | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/gdb/testsuite/gdb.dwarf2/implptrpiece.exp b/gdb/testsuite/gdb.dwarf2/implptrpiece.exp
> index af7dd37..3f6e0d6 100644
> --- a/gdb/testsuite/gdb.dwarf2/implptrpiece.exp
> +++ b/gdb/testsuite/gdb.dwarf2/implptrpiece.exp
> @@ -119,4 +119,7 @@ if ![runto_main] {
>      return -1
>  }
>
> -gdb_test "print/d p\[-1\]" " = 0"
> +# Access the second byte of s through an implicit pointer to the third
> +# byte of s, using a negative offset.  Compare that to the second byte of
> +# the short integer 1 in target byte order.
> +gdb_test "p/d p\[-1\] - ((signed char *)(short\[1\]){1})\[1\]" " = 0"
> --

Can we check the result of p[-1] explicitly for different endianness?
We can fill in the first two bytes of s with 0x5678, for example, and
it is expected to see different results of p[-1] for different endianness.

-- 
Yao (齐尧)