Hello, On Wed, 18 Jan 2023, Jakub Jelinek wrote:
> > > > > Partly OT, what is riscv not defaulting that on as well? Does it have > > > > > usable unwind info even without that option, something else? > > > > > > > > The RISC-V ABI does not address this, AFAICS. > > > > > > And neither do many other ABIs, still we default there to > > > -fasynchronous-unwind-tables because we've decided it is a good idea. > > > > That might or might not be, but in the context of this thread that's > > immaterial. Doing the same as the other archs will then simply hide the > > problem on risc-v as well, instead of fixing it. > > Yeah, that is why I've mentioned "Partly OT". We want this bug to be fixed > (but the fix is not what has been posted but rather decide what we want to > ask there; if it is at the end of compilation, whether it is at least one > function with that flag has been compiled, or all functions have been with > that flag, something else), The answer to this should be guided by normal use cases. The normal use case is that a whole input file is compiled with or without -funwind-tables, and not that individual functions change this. So any solution in which that usecase doesn't work is not a solution. The purest solution is to emit unwind tables for all functions that request it into .eh_frame and for those that don't request it put into .debug_frame (if also -g is on). If that requires enabling unwind-tables globally first (i.e. if even just one input function requests it) then that is what needs to be done. (this seems to be the problem currently, that the unwind-table activation on a per-function basis comes too late). The easier solution might be to make funwind-tables also be a global special-cased option for LTO (so that the usual use-case above works), that would trade one or another bug, but I'd say the current bug is more serious than the other bug that would be introduced. > and IMHO riscv should switch to > -fasynchronous-unwind-tables by default. I don't disagree, as long as that doesn't lead to the bug being ignored :) Ciao, Michael.
