Re: GDB 8.2 release 2018-08-21 status update

[Simon Marchi <simon.marchi@polymtl.ca>]

On 2018-08-24 14:35, Pedro Alves wrote:
> On 08/23/2018 11:41 PM, Kevin Buettner wrote:
>> Simon Marchi <simon.marchi@polymtl.ca> wrote:
> 
>>> So from my point of view, it would be fine to include it in 8.2.  I'm
>>> just wondering though why this was considered as a blocker for 8.2 in
>>> the first place.  It's not really a regression, it's more like a new
>>> feature.  Was it to make sure we get the feature to users faster, 
>>> before
>>> the new gcc that emits code like this by default starts to spread too
>>> much?
> 
> Yeah, the main issue here is that nowadays 
> -freorder-blocks-and-partition
> is on by default in GCC (I believe the switch was flipped in GCC 8?), 
> which
> means users will run into this problem more frequently going forward.  
> While
> technically it's not a GDB regression (you can always run into this if 
> you
> build your program with -freorder-blocks-and-partition explicitly), 
> from
> the perspective of end users looking at the toolchain as whole black 
> box,
> it's a toolchain regression (defaults no longer work).
> I'd support putting the series in GDB 8.2.

Seems nobody is against it.  Go!

> Unless I'm wrong that
> -freorder-blocks-and-partition is on by default in GCC 8 already?

Looking at gcc/doc/invoke.texi, apparently it's been enabled for -O2/-O3 
for some time and more recently -Os.  You can check whether it is 
enabled with:

   gcc -Q -v --help 2>/dev/null | grep reorder-blocks-and-partition

I see it as disabled by default and enabled if I add -O2, with different 
gcc versions between 5.4.0 and 8.2.0.  So it doesn't seem to have 
changed recently.  Maybe what changed is that gcc 8 partitions more 
aggressively?  Or it's just that gcc developers tend to debug -O2 
builds?  I have no idea.

Simon