[PATCH 0/6] DWARF Two Level Line Tables

[PATCH 0/6] DWARF Two Level Line Tables

[Doug Evans]

Hi.

This patch set adds Two Level Line Tables support to gdb,
as well as support for the DWARF 5 line table extensions.

http://wiki.dwarfstd.org/index.php?title=TwoLevelLineTables
http://www.dwarfstd.org/ShowIssue.php?issue=140906.1
http://www.dwarfstd.org/ShowIssue.php?issue=140724.1

The current version of the patch uses a gross hack because
consumers of debug info, including gdb, are not aggressive
enough in rejecting versions they don't understand.
So that existing gdbs won't crash when given the new line table
we create a DWARF 4 line header, and tuck the guts of the
two line tables (logicals + actuals) in something that looks
like a single entry.
Fortunately 7.9 won't crash, so the plan is to hopefully do
something more sensible.

The patch has been regression tested with existing debug info,
as well as the new two-level-line-table support on the google-4.9.x
gcc branch, and the binutils users/ccoutant/two-level-line-tables branch.

Re: [PATCH 0/6] DWARF Two Level Line Tables

[Yao Qi]

Doug Evans <dje@google.com> writes:

> This patch set adds Two Level Line Tables support to gdb,
> as well as support for the DWARF 5 line table extensions.

Hi Doug,
I notice that a lot of code is added into dwarf2read.c in this patch
set.  Is it possible to put them in a separated file or split
dwarf2read.c?  Every time, when I read dwarf2read.c, I find it is too
long to understand.  IWBN to split dwarf2read.c, at least, add new stuff
into a new file.

-- 
Yao (齐尧)

Re: [PATCH 0/6] DWARF Two Level Line Tables

[Doug Evans]

On Fri, Mar 13, 2015 at 10:32 AM, Yao Qi <qiyaoltc@gmail.com> wrote:
> Doug Evans <dje@google.com> writes:
>
>> This patch set adds Two Level Line Tables support to gdb,
>> as well as support for the DWARF 5 line table extensions.
>
> Hi Doug,
> I notice that a lot of code is added into dwarf2read.c in this patch
> set.  Is it possible to put them in a separated file or split
> dwarf2read.c?  Every time, when I read dwarf2read.c, I find it is too
> long to understand.  IWBN to split dwarf2read.c, at least, add new stuff
> into a new file.

dwarf2read.c is long overdue for a split.
[though this patch set can't just be put in a new file as it
just augments the line number support that is already there]

But I'm still trying to catch gcc's dwarf2out.c.
With this patch we're within 15KB, we've almost caught up! :-)

Re: [PATCH 0/6] DWARF Two Level Line Tables

[Doug Evans]

On Thu, Mar 12, 2015 at 12:58 PM, Doug Evans <dje@google.com> wrote:
> Hi.
>
> This patch set adds Two Level Line Tables support to gdb,
> as well as support for the DWARF 5 line table extensions.
>
> http://wiki.dwarfstd.org/index.php?title=TwoLevelLineTables
> http://www.dwarfstd.org/ShowIssue.php?issue=140906.1
> http://www.dwarfstd.org/ShowIssue.php?issue=140724.1
>
> The current version of the patch uses a gross hack because
> consumers of debug info, including gdb, are not aggressive
> enough in rejecting versions they don't understand.
> So that existing gdbs won't crash when given the new line table
> we create a DWARF 4 line header, and tuck the guts of the
> two line tables (logicals + actuals) in something that looks
> like a single entry.
> Fortunately 7.9 won't crash, so the plan is to hopefully do
> something more sensible.
>
> The patch has been regression tested with existing debug info,
> as well as the new two-level-line-table support on the google-4.9.x
> gcc branch, and the binutils users/ccoutant/two-level-line-tables branch.

I've committed the first four patches in this series,
which were just cleanups.

The remaining two patches add support for DWARF v5 line
tables as well as the proposed two level line tables.
Since stock gcc doesn't generate these yet my plan
is to hold off committing them for now.
I'm happy to commit them early if someone needs/wants me too.