thodg/libgit2/tests

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    Commit

  • Hash : 322c15ee
    Author : lhchavez
    Date : 2020-08-01T18:24:41 

    Make the pack and mwindow implementations data-race-free

This change fixes a packfile heap corruption that can happen when
interacting with multiple packfiles concurrently across multiple
threads. This is exacerbated by setting a lower mwindow open file limit.

This change:

* Renames most of the internal methods in pack.c to clearly indicate
  that they expect to be called with a certain lock held, making
  reasoning about the state of locks a bit easier.
* Splits the `git_pack_file` lock in two: the one in `git_pack_file`
  only protects the `index_map`. The protection to `git_mwindow_file` is
  now in that struct.
* Explicitly checks for freshness of the `git_pack_file` in
  `git_packfile_unpack_header`: this allows the mwindow implementation
  to close files whenever there is enough cache pressure, and
  `git_packfile_unpack_header` will reopen the packfile if needed.
* After a call to `p_munmap()`, the `data` and `len` fields are poisoned
  with `NULL` to make use-after-frees more evident and crash rather than
  being open to the possibility of heap corruption.
* Adds a test case to prevent this from regressing in the future.

Fixes: #5591

  • README.md

  • Writing Clar tests for libgit2

    For information on the Clar testing framework and a detailed introduction please visit:

    https://github.com/vmg/clar

    • Write your modules and tests. Use good, meaningful names.

    • Make sure you actually build the tests by setting: 

        cmake -DBUILD_CLAR=ON build/

    • Test: 

        ./build/libgit2_clar

    • Make sure everything is fine.

    • Send your pull request. That’s it.

    Memory leak checks

    These are automatically run as part of CI, but if you want to check locally:

    Linux

    Uses valgrind:

    $ cmake -DBUILD_CLAR=ON -DVALGRIND=ON ..
$ cmake --build .
$ valgrind --leak-check=full --show-reachable=yes --num-callers=50 --suppressions=../libgit2_clar.supp \
  ./libgit2_clar

    macOS

    Uses leaks, which requires XCode installed:

    $ MallocStackLogging=1 MallocScribble=1 MallocLogFile=/dev/null CLAR_AT_EXIT="leaks -quiet \$PPID" \
  ./libgit2_clar

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