From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gdb-testers-return-14691-listarch-gdb-testers=sources.redhat.com@sourceware.org>
Received: (qmail 119813 invoked by alias); 15 May 2015 14:49:59 -0000
Mailing-List: contact gdb-testers-help@sourceware.org; run by ezmlm
Precedence: bulk
List-Id: <gdb-testers.sourceware.org>
List-Subscribe: <mailto:gdb-testers-subscribe@sourceware.org>
List-Archive: <http://sourceware.org/ml/gdb-testers/>
List-Post: <mailto:gdb-testers@sourceware.org>
List-Help: <mailto:gdb-testers-help@sourceware.org>, <http://sourceware.org/ml/#faqs>
Sender: gdb-testers-owner@sourceware.org
Received: (qmail 119804 invoked by uid 89); 15 May 2015 14:49:58 -0000
Authentication-Results: sourceware.org; auth=none
X-Virus-Found: No
X-Spam-SWARE-Status: No, score=-0.8 required=5.0 tests=AWL,BAYES_00,KAM_LAZY_DOMAIN_SECURITY autolearn=no version=3.3.2
X-HELO: kwanyin.sergiodj.net
Received: from kwanyin.sergiodj.net (HELO kwanyin.sergiodj.net) (176.31.208.32) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-SHA encrypted) ESMTPS; Fri, 15 May 2015 14:49:57 +0000
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [binutils-gdb] [Ada] problem printing negative integer values in packed arrays.
From: sergiodj+buildbot@redhat.com
To: gdb-testers@sourceware.org
Message-Id: <9cd4d857bb046ad9be3c6d978b5b2aebb528eaf4@kwanyin>
Date: Fri, 15 May 2015 14:49:00 -0000
X-SW-Source: 2015-q2/txt/msg04403.txt.bz2

*** TEST RESULTS FOR COMMIT 9cd4d857bb046ad9be3c6d978b5b2aebb528eaf4 ***

Author: Joel Brobecker <brobecker@adacore.com>
Branch: master
Commit: 9cd4d857bb046ad9be3c6d978b5b2aebb528eaf4

[Ada] problem printing negative integer values in packed arrays.
Consider the following declarations:

   type Signed_Small is new Integer range - (2 ** 5) .. (2 ** 5 - 1);
   type Signed_Simple_Array is array (1 .. 4) of Signed_Small;
   pragma Pack (Signed_Simple_Array);
   SSA : Signed_Simple_Array := (-1, 2, -3, 4);

GDB currently print its value incorrectly for the elements that
are negative:

    (gdb) print ssa
    $1 = (65535, 2, 1048573, 4)
    (gdb) print ssa(1)
    $2 = 65535
    (gdb) print ssa(2)
    $3 = 2
    (gdb) print ssa(3)
    $4 = 1048573
    (gdb) print ssa(4)
    $5 = 4

What happens is that the sign-extension is not working because
we're trying to do left shift with a negative count. In
ada_value_primitive_packed_val, we have a loop which populates
the extra bits of the target (unpacked) value, after extraction
of the data from the original (packed) value:

        while (ntarg > 0)
          {
            accum |= sign << accumSize;
            unpacked[targ] = accum & ~(~0L << HOST_CHAR_BIT);
!!! ->      accumSize -= HOST_CHAR_BIT;
            accum >>= HOST_CHAR_BIT;
            ntarg -= 1;
            targ += delta;
          }

At each iteration, accumSize gets decremented by HOST_CHAR_BIT,
which can easily cause it to become negative, particularly on
little endian targets, where accumSize is at most HOST_CHAR_BIT - 1.
This causes us to perform a left-shift operation with a negative
accumSize at the next loop iteration, which is undefined, and
acutally does not produce the effect we wanted (value left untouched)
when the code is compiled with GCC.

This patch fixes the issue by simply setting accumSize to zero
if negative.

gdb/ChangeLog:

        * ada-lang.c (ada_value_primitive_packed_val): Make sure
        accumSize is never negative.

gdb/testsuite/ChangeLog:

        * gdb.ada/pckd_neg: New testcase.