Waits for a current transaction to finish in TEST_CompactRange when the
`background_work_finished_signal_` signal may be emitted due to an error. This is a prospective fix for flaky crashes observed in b/351680196#comment5.

PiperOrigin-RevId: 663457574

See https://github.com/google/leveldb/issues/1081

PiperOrigin-RevId: 499519182

Add logging with debugging information when failing to load a version set.

PiperOrigin-RevId: 351432332

PiperOrigin-RevId: 309110431

This CL makes the following substitutions.

* assert.h -> cassert
* math.h -> cmath
* stdarg.h -> cstdarg
* stddef.h -> cstddef
* stdint.h -> cstdint
* stdio.h -> cstdio
* stdlib.h -> cstdlib
* string.h -> cstring

PiperOrigin-RevId: 309080151

The "DeleteFile" method name causes pain for Windows developers, because
<windows.h> #defines a DeleteFile macro to DeleteFileW or DeleteFileA.
Current code uses workarounds, like #undefining DeleteFile everywhere an
Env is declared, implemented, or used.

This CL removes the need for workarounds by renaming Env::DeleteFile to
Env::RemoveFile. For consistency, Env::DeleteDir is also renamed to
Env::RemoveDir. A few internal methods are also renamed for consistency.
Software that supports Windows is expected to migrate any Env
implementations and usage to Remove{File,Dir}, and never use the name
Env::Delete{File,Dir} in its code.

The renaming is done in a backwards-compatible way, at the risk of
making it slightly more difficult to build a new correct Env
implementation. The backwards compatibility is achieved using the
following hacks:

1) Env::Remove{File,Dir} methods are added, with a default
    implementation that calls into Env::Delete{File,Dir}. This makes old
    Env implementations compatible with code that calls into the updated
    API.
2) The Env::Delete{File,Dir} methods are no longer pure virtuals.
    Instead, they gain a default implementation that calls into
    Env::Remove{File,Dir}. This makes updated Env implementations
    compatible with code that calls into the old API.

The cost of this approach is that it's possible to write an Env without
overriding either Rename{File,Dir} or Delete{File,Dir}, without getting
a compiler warning. However, attempting to run the test suite will
immediately fail with an infinite call stack ending in
{Remove,Delete}{File,Dir}, making developers aware of the problem.

PiperOrigin-RevId: 288710907

The local variable `updates` in DBImpl::Write was hiding the
`updates` parameter. Renamed to avoid this conflict.

PiperOrigin-RevId: 277089971

A recent change (4cb80b7ddc) to DBImpl::DeleteObsoleteFiles
unlocked DBImpl::mutex_ while deleting files to allow for
greater concurrency. This change improves on the prior in
a few areas:

1. The table is evicted from the table cache before unlocking
   the mutex. This should only improve performance.
2. This implementation is slightly simpler, but at the cost of
   a bit more memory usage.
3. A comment adding more detail as to why the mutex is being
   unlocked and why it is safe to do so.

PiperOrigin-RevId: 253111645

mutex_ was already acquired before accessing DBImpl::versions_ in all
but one place: DBImpl::GetApproximateSizes. This change requires mutex_
to be held before accessing versions_.

PiperOrigin-RevId: 248390814

Converted `for (;<condition>;)` to `while (<condition>)`.

PiperOrigin-RevId: 247950510

PiperOrigin-RevId: 247491163

1) Convert iterator-based for loops to C++11 foreach loops.
2) Convert "void operator=" to "T& operator=".
3) Switch from copy operators from private to public deleted.
4) Switch from empty ctors / dtors to "= default" where appropriate.

PiperOrigin-RevId: 246679195