Variable tracking (location lists support) - part 2

[Roger Sayle]

Hi Josef and Dan,

I've just discovered that typing "gdb cc1" on i686-pc-linux-gnu with
a recently built mainline GCC, causes both gdb 6.0 and gdb 5.2.1 to
segmentation fault.  Given that 6.0 is the most recent release of GDB,
I suspect that either there's a bug in gcc's location list generation
or that GDB's dwarf-2 location list code isn't as backwardly "safe"
as we'd hoped.

The segfault in gdb 6.0 is in decode_locdesc of dwarf2read.c line 6771,
where the value of the "blk" pointer looks invalid.

I'm looking into the issue as best I can (without a debugger :<), but
I wonder if I could also ask you to investigate?  As a worst case
scenario, we might consider a patch to disable location lists by
default, until this failure is resolved?

Many thanks in advance,

Roger
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