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Re: support for compilation units with discontiguous address ranges? (.debug_ranges)
- To: Jim Blandy <jimb at zwingli dot cygnus dot com>
- Subject: Re: support for compilation units with discontiguous address ranges? (.debug_ranges)
- From: Daniel Berlin <dan at cgsoftware dot com>
- Date: Fri, 20 Jul 2001 22:14:36 -0400
- Cc: Brian Grant <grant at transmeta dot com>, gdb at sources dot redhat dot com
- References: <200107192155.OAA10252@grant-linux2.transmeta.com><np1ynbthie.fsf@zwingli.cygnus.com>
Jim Blandy <jimb@zwingli.cygnus.com> writes:
> Brian Grant <grant@transmeta.com> writes:
>> Has anyone implemented dwarf2 support in gdb for compilation units with
>> discontiguous ranges of addresses?
>
> No. Patches are welcome!
>
>> gcc 3.x doesn't seem to produce .debug_ranges and gdb 5.0 doesn't
>> read it at all. gdb also seems to ignore .debug_aranges.
>
> That's right.
>
>> What currently happens in gdb is that all functions in .text1
>> and .text2 at addresses between foo() and bar() are attributed
>> the file and line number of the last line of foo(). Their real,
>> accurate line-number info is overshadowed completely.
>
> Right --- GDB misidentifies which compilation unit they belong to, so
> it never looks at the right compilation units' line tables.
>
>> I noticed that gcc doesn't produce DW_AT_low_pc/high_pc fields for
>> foobar.c, as it normally would for a DW_TAG_compilation_unit record,
>> where all functions in the compilation unit were in the same
>> section.
>
> Right, that's as required by the Dwarf 2 spec:
>
> The presence of low and high pc attributes in a compilation
> unit entry imply that the code generated for that compilation
> unit is contiguous and exists totally within the boundaries
> specified by those two attributes. If that is not the case,
> no low and high pc attributes should be produced.
>
> The Dwarf 2.1 spec says something similar.
>
>> Does anyone know of a workaround for this problem?
>
> I can only think of two options:
>
> 1) Don't do that. Put functions that need to go in separate segments
> in separate .c files.
>
> 2) Implement DW_AT_ranges support in GCC and GDB.
I have the first part of this done.
I just haven't submitted the patch yet, because i haven't had time to
update hte new dwarf2 reader to support it.
--
"When I woke up this morning my girlfriend asked me, "Did you
sleep good?" I said, "No, I made a few mistakes."
"-Steven Wright