https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117267
--- Comment #12 from Stas Sergeev <stsp at users dot sourceforge.net> --- Well I can move %rsp with an inline asm to some pre-defined buffer before recovering regs with swapcontext. Or I can manually adjust it in jmpbuf, in which case I won't be on a wrong stack even temporarily. Although I suspect you are going to declare both things an UB anyway. :)
