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[lldb] Turn lldb_private::Status into a value type. (#106163 )

This patch removes all of the Set.* methods from Status.

This cleanup is part of a series of patches that make it harder use the
anti-pattern of keeping a long-lives Status object around and updating
it while dropping any errors it contains on the floor.

This patch is largely NFC, the more interesting next steps this enables
is to:
1. remove Status.Clear()
2. assert that Status::operator=() never overwrites an error
3. remove Status::operator=()

Note that step (2) will bring 90% of the benefits for users, and step
(3) will dramatically clean up the error handling code in various
places. In the end my goal is to convert all APIs that are of the form

`    ResultTy DoFoo(Status& error)
`
to

`    llvm::Expected<ResultTy> DoFoo()
`
How to read this patch?

The interesting changes are in Status.h and Status.cpp, all other
changes are mostly

` perl -pi -e 's/\.SetErrorString/ = Status::FromErrorString/g' $(git
grep -l SetErrorString lldb/source)
`
plus the occasional manual cleanup.

2024-08-27 10:59:31 -07:00

copy-sparse.py

…

libfbsdvmcore-hacks.patch

…

lldb-minimize-processes.patch

[lldb] Turn lldb_private::Status into a value type. (#106163 )

2024-08-27 10:59:31 -07:00

README.rst

…

test.script

…

README.rst

How to create vmcores for tests
===============================

1. Boot a FreeBSD VM with as little memory as possible and create a core dump
   per `FreeBSD Handbook Kernel Debugging Chapter`_.  Note that you may need to
   reboot with more memory after the kernel panic as otherwise savecore(8) may
   fail.

   For instance, I was able to boot FreeBSD and qemu-system-x86_64 with 128 MiB
   RAM but had to increase it to 256 MiB for the boot after kernel panic.

2. Transfer the kernel image (``/boot/kernel/kernel``) and vmcore
   (``/var/crash/vmcore.latest``) from the VM.

3. Patch libfbsdvmcore using ``libfbsdvmcore-hacks.patch`` and build LLDB
   against the patched library.

4. Patch LLDB using ``lldb-minimize-processes.patch`` and build it.

   WARNING: LLDB will now modify core files in order to make the resulting
   test vmcores smaller.  Make a backup if necessary.

5. Do a test run of ``test.script`` in LLDB against the kernel + vmcore::

    lldb -b -s test.script --core /path/to/core /path/to/kernel

   If everything works fine, the LLDB output should be interspersed with
   ``%RD`` lines.  The vmcore will also be modified to shorten the process
   list in ``allproc``.

6. Open the vmcore in the patched LLDB again and choose interesting threads
   for testing.  Update thread numbers in ``test.script`` if necessary.

7. Use the ``copy-sparse.py`` tool to create a sparse version of the vmcore::

       lldb -b -s test.script --core /path/to/core /path/to/kernel |
           grep '^% RD' | python copy-sparse.py /path/to/core vmcore.sparse

8. Compress the sparse vmcore file using ``bzip2``::

       bzip2 -9 vmcore.sparse


.. _FreeBSD Handbook Kernel Debugging Chapter:
   https://docs.freebsd.org/en/books/developers-handbook/kerneldebug/