[Bug 1960005] Re: Exceptions crash

[Launchpad Bug Tracker]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: google-glog (Ubuntu)
       Status: New => Confirmed

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https://bugs.launchpad.net/bugs/1960005

Title:
  Exceptions crash

Status in google-glog package in Ubuntu:
  Confirmed
Status in libunwind package in Ubuntu:
  Confirmed

Bug description:
  There is a serious bug in libunwind 1.2.1 on
  Ubuntu 20.04 which causes a crash when
  handling exceptions (C++ in my case).

  I have observed libunwind incorrectly
  restoring registers while executing DWARF
  opcodes in .eh_frame. In my case, the restore
  of the register r6 (rbp on x86-64) was
  prematurely commited. In certain complex
  scenarios with optimization enabled,
  gcc emits DWARF instructions which express
  the offsets for save addresses
  of higher-numbered registers against rbp
  (instead of against the canonical frame
  address, as is usual).
  If rbp is prematurely committed,
  higher-numbered registers are
  restored incorrectly, i.e. corrupted.

  I have described the issue in great detail at
  https://gcc.gnu.org/pipermail/gcc-help/2022-February/141189.html

  The current version on Arch (1.6.x) seems
  to have this bug fixed. I don’t known at
  which  point or which bug was it exactly,
  but it would be a really good idea to
  backport this fix.

  In my case, my application had libunwind
  linked in instead of using the builting gcc
  unwinder due to a 3rd party dependency,
  Google glog, used by the Google Ceres
  solver. However, it is only an optional
  dependency, and glog can be built without
  libunwind (it is just the preferred unwinder
  for printing stack dumps in glog).

  I had to rebuild glog without libunwind
  to stop my application from crashing
  (the builtin gcc unwinder works fine).

  Google has a strict policy against using
  C++ exceptions so I’m not surprised that
  they haven’t stumbled upon this.

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