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From: Andreas Arnez <>
To: "Rohr, Stephan via Gdb" <>
Cc: "Rohr, Stephan" <>, "Tom Tromey" <>
Subject: Re: Issue in dwarf2/expr.c
Date: Thu, 14 Apr 2022 15:51:59 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <> (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 --

	* dwarf2loc.c (read_pieced_value): Work properly when 'v' has an
	(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


  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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