Re: [PATCH v2 1/2] perf bench: Fix initialization of union

[Namhyung Kim <namhyung@kernel.org>]

On Thu, Feb 19, 2026 at 11:00:41AM -0800, Namhyung Kim wrote:
> Hello,
> 
> On Thu, Feb 19, 2026 at 03:02:56PM +0000, Leo Yan wrote:
> > On Thu, Feb 19, 2026 at 10:38:57AM +0000, James Clark wrote:
> > > 
> > > 
> > > On 19/02/2026 10:36 am, James Clark wrote:
> > > > 
> > > > 
> > > > On 19/02/2026 12:44 am, Namhyung Kim wrote:
> > > > > Recent compilers don't initialize all members (or the largest member) in
> > > > > an union.  Instead it seems to set the first member only.  So some perf
> > > > > bench output shows invalid numbers like below on my system with GCC 15.
> > > > 
> > > > I couldn't find V1 of this so I wasn't sure if it was discussed already,
> > > > but wasn't the plan to fix this with a compiler option:
> > > > 
> > > > https://lore.kernel.org/linux-perf-users/20250319110454.3230687-1-leo.yan@arm.com/
> > > > 
> > > > and
> > > > 
> > > > https://lore.kernel.org/linux-perf-users/20250320105235.3498106-1-leo.yan@arm.com/
> > > 
> > > Oh I see V1 was only the second patch, that's why I couldn't find it.
> > 
> > Thanks for bringing up this, James.  The latest patch would be:
> > 
> > https://lore.kernel.org/lkml/20250402173056.829400-1-leo.yan@arm.com/
> > 
> > This patch intends to apply the option across tools, but no response
> > from the maintainers.  Seems to me, it may be good enought to apply the
> > option to perf first.
> 
> Thanks for the reminder, yeah it looks better.

Leo, can you please resend that patch to linux-kbuild list and CC the
maintainers?  It seems you did it to Clang folks only..

Thanks,
Namhyung