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Thu, 14 Apr 2022 13:52:00 +0000 (GMT) Received: from li-07e5db4c-3052-11b2-a85c-815382633c95.ibm.com (unknown [9.152.222.38]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Thu, 14 Apr 2022 13:52:00 +0000 (GMT) To: "Rohr, Stephan via Gdb" Subject: Re: Issue in dwarf2/expr.c Organization: IBM Deutschland Research & Development GmbH References: Date: Thu, 14 Apr 2022 15:51:59 +0200 In-Reply-To: (Stephan via Gdb Rohr's message of "Wed, 13 Apr 2022 16:57:51 +0000") Message-ID: <877d7reps0.fsf@li-07e5db4c-3052-11b2-a85c-815382633c95.ibm.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: XvvkFVNbJ047e0iOJfWE6Of7mDJgrqAH X-Proofpoint-GUID: XvvkFVNbJ047e0iOJfWE6Of7mDJgrqAH X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.858,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-04-14_04,2022-04-14_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 impostorscore=0 bulkscore=0 suspectscore=0 mlxlogscore=862 spamscore=0 mlxscore=0 phishscore=0 priorityscore=1501 malwarescore=0 lowpriorityscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2204140074 X-BeenThere: gdb@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Andreas Arnez via Gdb Reply-To: Andreas Arnez Cc: Tom Tromey Errors-To: gdb-bounces+public-inbox=simark.ca@sourceware.org Sender: "Gdb" On Wed, Apr 13 2022, Rohr, Stephan via Gdb wrote: > Hi all, > > I came across a bug in dwarf2/expr.c:177 in function rw_pieced_value. when reading a pieced value described by DW_OP_piece or DW_OP_bit_piece. > > if (value_type (v) != value_enclosing_type (v)) > internal_error (__FILE__, __LINE__, > _("Should not be able to create a lazy value with " > "an enclosing type")); Since I did some work on this function in the past, I just looked where this check comes from, and it turns out that it was introduced in 2010 by Tom Tromey with commit afd74c5ff76010405caddd2834be4a0178fa93dd -- gdb * dwarf2loc.c (read_pieced_value): Work properly when 'v' has an offset. (write_pieced_value): Likewise. Perhaps Tom still remembers the rationale? > > This check can easily be triggered when casting a variable with location described by DW_OP_piece or DW_OP_bit_piece. > > A minimal reproducer can be found in gdb/testsuite/gdb.dwarf2/shortpiece.exp, e.g. casting s1 to an array type triggers the error > > p (short []) s1 > > I currently struggle to understand the reasoning for this check. I could think of changing this to > > if (TYPE_LENGTH(value_type (v)) > TYPE_LENGTH( value_enclosing_type (v))) > to support the cast operation. > > But in general, I'm not sure why this check is needed at all. > > I appreciate your feedback. > > > Best > stephan -- Andreas