On Wed, 3 Feb 2021 20:29:48 GMT, Gerard Ziemski <gziem...@openjdk.org> wrote:
>> Part of the comment said `This work-around is not necessary for 10.5+, as >> CrashReporter no longer intercedes on caught fatal signals.` so I thought it >> was no longer needed, but it sounds like the part about `gdb` still applies >> then. >> >> We should update the comment to just say the `gdb` relevant part perhaps >> (and evaluate which of the EXC_MASK_BAD_ACCESS | EXC_MASK_BAD_INSTRUCTION | >> EXC_MASK_ARITHMETIC) we actually need for gdb: >> >> `// gdb installs both standard BSD signal handlers, and mach exception` >> `// handlers. By replacing the existing task exception handler, we disable >> gdb's mach` >> `// exception handling, while leaving the standard BSD signal handlers >> functional.` >> >> Do you know if this also apply to `lldb` or is it `gdb` only specific? How >> do you run `gdb` on macOS nowadays anyhow? > > To answer my own question, it seems that code is still needed on `x86_64` for > `lldb` with `EXC_MASK_BAD_ACCESS` or we keep tripping over `EXC_BAD_ACCESS` > > Remaining questions: > > a) why we need `EXC_MASK_ARITHMETIC` ? > b) we hit `signal SIGSEGV` in debugger even with the code in place, any way > to avoid that? > c) does `BSD aarch64` need only `EXC_MASK_BAD_INSTRUCTION` or does it need > `EXC_MASK_BAD_ACCESS` as well? > d) can we `#ifdef` the `EXC_MASK_BAD_INSTRUCTION` part of the mask only to > apply to `aarch64`? Thanks for your questions Gerard. > Part of the comment said This work-around is not necessary for 10.5+, as > CrashReporter no longer intercedes on caught fatal signals. That comment can probably be deleted since minversion is anyway 10.9 (and soon 10.12 https://github.com/openjdk/jdk/pull/2268 ). > Do you know if this also apply to lldb or is it gdb only specific? How do you > run gdb on macOS nowadays anyhow? `lldb` is shipped with Xcode, `gdb` isn't. You would need to build and sign it yourself, I haven't tried that in a while. So, we should update that comment to talk about `lldb` 🙂 > a) why we need `EXC_MASK_ARITHMETIC` ? I _believe_ this dates back to i386. As far as I can tell this isn't needed for x86_64 or aarch64. I guess we can remove it, the worst case is that it makes the debugging experience of the runtime a little bit worse. OTOH it doesn't hurt either to have it here. > b) we hit signal SIGSEGV in debugger even with the code in place, any way to > avoid that? The equivalent for `handle SIGSEGV nostop noprint` (gdb) in lldb is `process handle -n false -p true -s false SIGSEGV`. > c) does `BSD aarch6` need only `EXC_MASK_BAD_INSTRUCTION` or does it need > `EXC_MASK_BAD_ACCESS` as well? aarch64 needs `EXC_MASK_BAD_ACCESS` at least for implicit null checking, there might be other cases. > d) can we `#ifdef` the `EXC_MASK_BAD_INSTRUCTION` part of the mask only to > apply to `aarch64`? Maybe. I don't see any value in it though, except making the code more complicated to read 🙂 ------------- PR: https://git.openjdk.java.net/jdk/pull/2200
