delta/libgit2.git/tests/threads/atomic.c, branch ethomson/find_executable github.com: libgit2/libgit2.git Homogenize semantics for atomic-related functions 2021-08-26T12:34:17+00:00 lhchavez lhchavez@lhchavez.com 2020-12-20T20:45:01+00:00 74708a813d586df3ba22a81b475f6aba0498e2ef There were some subtle semantic differences between the various implementations of atomic functions. Now they behave the same, have tests and are better documented to avoid this from happening again in the future. Of note: * The semantics chosen for `git_atomic_compare_and_swap` match `InterlockedCompareExchangePointer`/`__sync_cal_compare_and_swap` now. * The semantics chosen for `git_atomic_add` match `InterlockedAdd`/`__atomic_add_fetch`. * `git_atomic_swap` and `git_atomic_load` still have a bit of semantic difference with the gcc builtins / msvc interlocked operations, since they require an l-value (not a pointer). If desired, this can be homogenized. 
There were some subtle semantic differences between the various
implementations of atomic functions. Now they behave the same, have
tests and are better documented to avoid this from happening again in
the future.

Of note:

* The semantics chosen for `git_atomic_compare_and_swap` match
  `InterlockedCompareExchangePointer`/`__sync_cal_compare_and_swap` now.
* The semantics chosen for `git_atomic_add` match
  `InterlockedAdd`/`__atomic_add_fetch`.
* `git_atomic_swap` and `git_atomic_load` still have a bit of semantic
  difference with the gcc builtins / msvc interlocked operations, since
  they require an l-value (not a pointer). If desired, this can be
  homogenized.