Created attachment 538310 [details] emerge --info x11-libs/libxcb The native Linux port can't start when it's using the system's libxcb. Copying libxcb.so.1 and libxcb-dri3.so.0 from Steam i386 runtime into the directory where Civ5XP binary is located relieves the issue.
Created attachment 538312 [details] gdb ./Civ5XP
Just running it in gdb is not very helpful. Run the "bt" command in gdb to obtain a backtrace.
Created attachment 538316 [details] running bt inside of gdb that started Civ5XP
Civ5BE seems to have this issue as well as Civ5XP. Civ6 seems to work. I didn't pinpoint this to a xcb upgrade, but it does indeed have xcb in the stacktraces.
Is that related to bug 616402? Especially bug 616402 comment 11?
Chí-Thanh Christopher Nguyễn: recompiling x11-libs/libxcb with -mstackrealign helped :) No CFLAGS needed to be gutted, just add the stack realign to default CFLAGS.
*** This bug has been marked as a duplicate of bug 616402 ***