x11-libs/libX11 causes plasmashell to crash at startup if built with -fipa-pta

[asaparov]

So I know I have some -fipa-pta issues that others don't, but I wanted to just report this anyway. When I build x11-libs/libx11-1.6.8 or 1.6.7 with -fipa-pta, then whenever KDE starts up, plasmashell segfaults (or sometimes is killed with a "general protection error"), and so I'm left with a black screen with a cursor. There are no issues during compilation.

[InBetweenNames]

Really curious here -- I actually use Plasma on a near daily basis with -fipa-pta on x11-libs/libx11 without any issues. This combined with your two PRs is really perplexing. I'd really like to get to the bottom of what's going on here.

[zkvsky]

I'm using plasma on a daily basis without such issues and with -fipa-pta, we need more context

[asaparov]

Me too, I have plasma on two of my machines and both of them have this problem. I've noted this in earlier issues and pull requests since it affects other packages too (see #308, #364, and #365). @InBetweenNames mentioned that someone else is also experiencing this, and I really don't know why most others don't have this issue.

On my systems, I am not using LTO but I am using -Ofast. But I've found that these issues still arise with -O2 (though I haven't tried rebuilding my entire system with -O2). As noted in #308, I found that compiling with LTO resolves the issue. I haven't tested building libX11 with LTO.

[jiblime]

I know I have some -fipa-pta issues that others don't

Are you using different CFLAGS or have much newer hardware? The fact that it is affecting multiple packages may be a clue. Although it could be just an -Ofast issue...

[asaparov]

I think its more likely related to not using LTO rather than -Ofast since I've been able to reproduce many of these with -O2.

[asaparov]

My hardware isn't especially new. It's all from 2015 except for my GPU which is a 1080 Ti. It also happens on my laptop which is an MSI GS63VR from 2016.

[elsandosgrande]

@asaparov Could you try running Wayland? If XWayland works (a Wayland wrapper for the X server), then we might be looking at a strange issue. Do provide us with your make.conf file and your emerge --info x11 plasma-meta output as well.

To run Wayland, just add the wayland USE flag and run emerge --newuse @world. I tend to add --verbose as well.

Edit

It just hit me that it is easier to get up and running with Wayland on Gentoo than on Arch Linux. To this day, I cannot recall what the necessary packages are for running Wayland.