From: Andreas Arnez <arnez@linux.ibm.com>
To: "Rohr, Stephan via Gdb" <gdb@sourceware.org>
Cc: "Rohr, Stephan" <stephan.rohr@intel.com>, "Tom Tromey" <tom@tromey.com>
Subject: Re: Issue in dwarf2/expr.c
Date: Thu, 14 Apr 2022 15:51:59 +0200 [thread overview]
Message-ID: <877d7reps0.fsf@li-07e5db4c-3052-11b2-a85c-815382633c95.ibm.com> (raw)
In-Reply-To: <DM6PR11MB456405A1FA95FA5498049AC093EC9@DM6PR11MB4564.namprd11.prod.outlook.com> (Stephan via Gdb Rohr's message of "Wed, 13 Apr 2022 16:57:51 +0000")
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
next prev parent reply other threads:[~2022-04-14 13:52 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-13 16:57 Rohr, Stephan
2022-04-14 13:51 ` Andreas Arnez [this message]
2022-04-15 20:24 ` Tom Tromey
2022-04-19 6:28 ` Rohr, Stephan
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