Re: [PATCH] PR debug/47471 (set prologue_end in .debug_line)

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

On Thu, 31 Mar 2011 04:59:18 +0200, Richard Henderson wrote:
> On 03/30/2011 11:19 AM, Dodji Seketeli wrote:
> > First, it avoids emitting two consecutive .loc that are identical.
> > Strictly speaking that should fix this issue in this particular case.
> 
> What's the compatibility strategy?  I.e. how does gdb tell that we're
> not using the double-loc mechanism?  Does it scan the line ops and if
> you see any prologue_end marks assume that double-loc is not in effect?

Currently GDB ignores / has no support for DW_LNS_set_prologue_end.


> Are you actually going to be able to delete any code within gdb, due
> to the need to interpret older debug info?

No code is going to be deleted from GDB.


For -O2 -g code the prologue does not (will not) need to be known to GDB:
	[patch] Do not skip prologue for -O2 -g with GCC VTA Re: [patch] Fix for PR gdb/12573
	http://sourceware.org/ml/gdb-patches/2011-03/msg01129.html

For -O0 -g code the line number information may be good enough.  For
compatibility with older GDBs the line number tricks should remain in place
and in such case DW_LNS_set_prologue_end is redundant for -O0 -g.

I thought DW_LNS_set_prologue_end would be cleaner for -O0 -g but that may not
be required.


Thanks,
Jan