Summary:
This diff contains trivial fixes for 6 scan-build warnings:

**db/c_test.c**
`db` variable is never read. Removed assignment.
scan-build report:
http://home.fburl.com/~sugak/latest20/report-9b77d2.html#EndPath

**db/db_iter.cc**
`skipping` local variable is assigned to false. Then in the next switch block the only "non return" case assign `skipping` to true, the rest cases don't use it and all do return.
scan-build report:
http://home.fburl.com/~sugak/latest20/report-13fca7.html#EndPath

**db/log_reader.cc**
In `bool Reader::SkipToInitialBlock()` `offset_in_block` local variable is assigned to 0 `if (offset_in_block > kBlockSize - 6)` and then never used. Removed the assignment and renamed it to `initial_offset_in_block` to avoid confusion.
scan-build report:
http://home.fburl.com/~sugak/latest20/report-a618dd.html#EndPath

In `bool Reader::ReadRecord(Slice* record, std::string* scratch)` local variable `in_fragmented_record` in switch case `kFullType` block is assigned to false and then does `return` without use. In the other switch case `kFirstType` block the same `in_fragmented_record` is assigned to false, but later assigned to true without prior use. Removed assignment for both cases.
scan-build reprots:
http://home.fburl.com/~sugak/latest20/report-bb86b0.html#EndPath
http://home.fburl.com/~sugak/latest20/report-a975be.html#EndPath

**table/plain_table_key_coding.cc**
Local variable `user_key_size` is assigned when declared. But then in both places where it is used assigned to `static_cast<uint32_t>(key.size() - 8)`. Changed to initialize the variable to the proper value in declaration.
scan-build report:
http://home.fburl.com/~sugak/latest20/report-9e6b86.html#EndPath

**tools/db_stress.cc**
Missing `break` in switch case block. This seems to be a bug. Added missing `break`.

Test Plan:
Make sure all tests are passing and scan-build does not report 'Dead assignment' and 'Dead initialization' bugs.
```lang=bash
% make check
% make analyze
```

Reviewers: meyering, igor, kradhakrishnan, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33795

Summary:
The unit test was supposed to check that the old file and the new file contains
the header message.

Test Plan: Run the unit test.

Reviewers: sdong

Reviewed By: sdong

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33705

Summary:
* Makefile (WARNING_FLAGS): Add -W and -Wextra, and at least for now,
-Wno-unused-parameter.  Without that latter one, there would be
many errors/warnings about unused parameters.

Test Plan:
run these and ensure there is no warning:
  make clean && make
  make clean && USE_CLANG=1 make

Reviewers: ljin, sdong, igor.sugak, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33819

Summary:
The "const" attribute applies to the type, and placing it
before that return type retains the desired semantics,
yet avoids the compiler error/warning.

Test Plan: Run make

Reviewers: ljin, sdong, igor.sugak, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33789

Summary: as above

Test Plan:
  Run "make EXTRA_CXXFLAGS='-W -Wextra'" and see fewer errors.

Reviewers: ljin, sdong, igor.sugak, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33753

Summary:
Otherwise, we would assert that an unsigned expression is always >= 0.
The intent was to form a possibly negative number, and to assert that
that value is always >= 0, but since one variable in the computation
was unsigned, the result was guaranteed to be unsigned, too, rendering
the assertion useless.

Cast that unsigned variable to "int", so that all operands
are signed, and thus so that the result can be negative.

Test Plan:
  Run "make EXTRA_CXXFLAGS='-W -Wextra'" and see fewer errors.

Reviewers: ljin, sdong, igor.sugak, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33771

Summary:
Adding -W and -Wextra to CXXFLAGS provoked this failure:

	  table/table_test.cc:1854:56: error: missing initializer for member ‘rocksdb::TestArgs::format_version’ [-Werror=missing-field-initializers]
	     TestArgs args = { DB_TEST, false, 16, kNoCompression };
	                                                          ^

Add the missing, 5th value (format_version).

Test Plan:
  Run "make EXTRA_CXXFLAGS='-W -Wextra'" and see fewer errors.

Reviewers: ljin, sdong, igor.sugak, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33765

Summary:
The "const" attribute does not make sense on a return type,
and provokes a warning/error from gcc -W -Wextra.

Test Plan:
  Run "make EXTRA_CXXFLAGS='-W -Wextra'" and see fewer errors.

Reviewers: ljin, sdong, igor.sugak, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33759

Summary:
Remove some always-true assertions.
They provoke these compilation failures:

  table/plain_table_key_coding.cc:279:20: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits]
  db/version_set.cc:336:15: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits]

* table/plain_table_key_coding.cc (rocksdb): Remove assertion that
unsigned type variable is >= 0.
* db/version_set.cc (DoGenerateLevelFilesBrief): Likewise.

Test Plan:
  Run "make EXTRA_CXXFLAGS='-W -Wextra'" and see fewer errors.

Reviewers: ljin, sdong, igor.sugak, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33747

Summary:
During running AutoRollLoggerTest on FreeBSD we have found out that AutoRollLogger is not flushing correctly (test fails on FreeBSD)
This diff add Flush to AutoRollLogger to fix this problem

Test Plan:
[My machine] make all check ( all tests pass)
[FreeBSD VM] running AutoRollLoggerTest ( all tests pass )

Reviewers: sdong, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33633

Summary:
In mongo, we currently have a single column family and I'd like to support setting rocksdb::Options from string. This diff provides an option to GetOptionsFromString()

There's one more problem. Currently GetColumnFamilyOptionsFromString() overwrites block_based options. In mongo I set default values for block_cache and some other values of BlockBasedTableOptions and I don't want them reset to default with GetOptionsFromString().

Test Plan: added unit test

Reviewers: yhchiang, rven, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33729

Summary:
The bug is detected by scan-build.

In `void WriteSeqSeekSeq(ThreadState* thread)` memory is allocated in line 3118 `Slice key = AllocateKey();` but `Slice` is not responsible deleting `Slice::data()`.

Added `std::unique_ptr<const char[]>*` parameter to ` AllocateKey()`, so that it requires caller to not forget about Slice::data() management.

scan-build bug report: http://home.fburl.com/~sugak/latest6/report-6e9754.html#EndPath

Test Plan:
Make sure scan-build does not report 'Memory leak' in db/db_bench.cc and all tests are passing.
```lang=bash
% make analyze
% make check
```

Reviewers: lgalanis, igor, meyering, sdong

Reviewed By: meyering, sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33501

Summary:
scan-build is reporting two memory leak bugs in `table/block_based_table_reader.cc`. They are both false positives. In both cases we allocate memory in `ReadBlockFromFile` if `s.ok()`. Then after the function `ReadBlockFromFile` returns we check for the same variable if `s.ok()` and then use the memory that was allocated. The bugs reported by scan-build is if `ReadBlockFromFile` allocates memory and returns, but for some reason status `s` is not the same and `s.ok() != true`.

In this case scan-build is concerned that memory owner transfer is not explicit. I modified `ReadBlockFromFile` to accept `std::unique_ptr<Block>*` as a parameter, instead of raw pointer.

scan-build reports:
http://home.fburl.com/~sugak/latest2/report-a4b3fa.html#EndPath
http://home.fburl.com/~sugak/latest2/report-29adbf.html#EndPath

Test Plan:
Make sure scan-build does not report these bugs and all tests are passing.
```lang=bash
% make check
% make analyze
```

Reviewers: sdong, lgalanis, meyering, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33681

Summary:
Prior to this change, "make check" would always waste a lot of
time relinking 60+ binaries. With this change, it does that
only when the generated file, util/build_version.cc, changes,
and that happens only when the date changes or when the
current git SHA changes.

This change makes some other improvements: before, there was no
rule to build a deleted util/build_version.cc. If it was somehow
removed, any attempt to link a program would fail.
There is no longer any need for the separate file,
build_tools/build_detect_version.  Its functionality is
now in the Makefile.

* Makefile (DEPFILES): Don't filter-out util/build_version.cc.
No need, and besides, removing that dependency was wrong.
(date, git_sha, gen_build_version): New helper variables.
(util/build_version.cc): New rule, to create this file
and update it only if it would contain new information.
* build_tools/build_detect_platform: Remove file.
* db/db_impl.cc: Now, print only date (not the time).
* util/build_version.h (rocksdb_build_compile_time): Remove
declaration.  No longer used.

Test Plan:
- Run "make check" twice, and note that the second time no linking is performed.
- Remove util/build_version.cc and ensure that any "make"
command regenerates it before doing anything else.
- Run this: strings librocksdb.a|grep _build_.
That prints output including the following:

  rocksdb_build_git_date:2015-02-19
  rocksdb_build_git_sha:2.8.fb-1792-g3cb6cc0

Reviewers: ljin, sdong, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33591

Summary: Add a DB property about live versions. It can be helpful to figure out whether there are files not live but not yet deleted, in some use cases.

Test Plan: make all check

Reviewers: rven, yhchiang, igor

Reviewed By: igor

Subscribers: yoshinorim, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33327

Summary:
The "ar" command was excessively verbose.
This abbreviates it to be like CC and LD.
Also, factor "rs" options into ARFLAGS.

Test Plan:
  $ rm librocksdb.a
  $ make librocksdb.a
  AR       librocksdb.a
  ar: creating librocksdb.a

Reviewers: ljin, sdong, igor.sugak, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33699

This reverts commit 7ce1b2c1.

Summary: Replaced rapidjson with fbson

Test Plan:
make all check
make valgrind_check

Reviewers: golovachalexander, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D32733

Summary:
This is a diff for managed iterator. A managed iterator
is a wrapper around an iterator which saves the options for that
iterator as well as the current key/value so that the underlying iterator
and its associated memory can be released when it is aged out
automatically or on the request of the user. Will provide the automatic release as a follow-up diff.

Test Plan: Managed* tests in db_test and XF tests for managed iterator

Reviewers: igor, yhchiang, anthony, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D31401

Summary:
  Many link commands were identical.
  Factor that out into a variable, AM_LINK, and use
  it in place of all of those open-coded commands.

Test Plan: run "make check"

Reviewers: ljin, igor, sdong

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33585

Summary:
With this change, make now prints a summary line for each
compiler and linker invocation, e.g.,:

  CC       db/builder.o
  CC       db/c.o
  CC       db/column_family.o

To see full commands, insert "V=1" into your make command.
E.g., run "make V=1 all" if you want it to print each command
in its full glory.

$^ is GNU make's abbreviation for the prerequisites of the current target.
These AM_V_... variables expand to some very short string like "CC" or
"LD", by default, so that the output of "make" is readable.  If/when you
want more details, just build with "make V=1 ...", and make will print
each full command as it is executed.  If you prefer to see the noise
all the time, and only want to optionally see the abbreviated output,
set AM_DEFAULT_VERBOSITY=1 in your environment, and then build with
V=0 to see the abbreviated command indicators.

Test Plan:
invoke make a few different ways and observe:
  make clean; make       # abbreviated
  make clean; make V=0   # also abbreviated
  make clean; make V=1   # full detail

Reviewers: sdong, ljin, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33579

Summary:
This is in preparation for some factorization.
* Makefile (deletefile_test): Add $(COVERAGEFLAGS) to link command.
(options_test): Remove explicit (redundant) dependency on
options_helper.o: that is already a dependent, via $(LIBOBJECTS)

Test Plan: run make

Reviewers: sdong, ljin, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33573

Summary:
There were Makefile rules to build those two targets,
but neither rule has worked for a long time, due to missing
dependent source files.  Remove those rules.

Test Plan: run "make"

Reviewers: sdong, ljin, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33567

Summary:
scan-build complains with division by zero warning in a test. Added an assertion to prevent this.

scan-build report: http://home.fburl.com/~sugak/latest6/report-c61be9.html#EndPath

Test Plan:
Make sure scan-build does not report 'Division by zero' and all tests are passing.
```lang=bash
% make analyze
% make check
```

Reviewers: igor, meyering

Reviewed By: meyering

Subscribers: sdong, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33495

Summary:
Remove ThreadStatusMultiCompaction test as it's currently written
in a way that depends on some randomness, while the flush / compaction
status of a single thread is also covered in ThreadStatusFlush
and ThreadStatusSingleCompaction tests.

Test Plan: ./db_test

Reviewers: igor, sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33537

Summary:
Add thread_status_util_debug.cc back as InstrumentedMutex related tests
are using it to produce wait that can be reflected in the counter.

Test Plan:
./perf_context_test
export ROCKSDB_TESTS=MutexWaitStats
./db_test

Reviewers: sdong, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33525

Summary:
Before this change, running "make" with no arguments would
silently run the rules for the "uninstall" target(!).  Don't do that.
* Makefile (default): New, first target; depend on "all".
(uninstall, install): Do not hide the commands we run.

Test Plan:
  Run "make" and verify that the rules for "uninstall" are no longer run.
  Instead, note that many files are compiled and linked.  Before, none were.

Reviewers: sdong, ljin, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33531

Summary: Allow GetThreadList to reflect flush activity.

Test Plan:
Developed ThreadStatusFlush test and updated ThreadStatusMultiCompaction test.

./db_test  ./thread_list_test

Reviewers: sdong, rven, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D32871

Summary:
* Makefile (dummy): Prefix this statement with "dummy := ",
so that it no longer triggers a syntax error from GNU make 3.80
and earlier.  Reported by nielsl in
https://github.com/facebook/rocksdb/issues/509

Test Plan: run make

Reviewers: sdong, ljin, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33429

Summary:
In the existing implementation of `ASSERT*`, test termination happens in `~Tester`, which is called when instance of `Tester` goes out of scope. This is the cause of many scan-build bugs.

This diff changes `ASSERT*` to terminate the test immediately. Also added one suppression in `util/signal_test.cc`

scan-build bugs
before: http://home.fburl.com/~sugak/latest/index.html
after: http://home.fburl.com/~sugak/latest2/index.html

Test Plan:
Modify some test to fail an assertion and make sure that `ASSERT*` terminated the test.

Run `make analyze` and make sure no 'Called C++ object pointer is null' and 'Dereference of null pointer' bugs reported.

Run tests and make sure no failing tests:
```lang=bash
% make check
% USE_CLANG=1 make check
```

Reviewers: meyering, lgalanis, sdong, rven, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33381

Summary:
The code being removed would invoke sed differently to work
around a portability difference in how sed -i works (different
on MacOS).  Yet performing a host-type-based ifdef fails when
the tools installed do not match.  That sed use was solely to
post-process the .d file.  Instead, generate the desired output
directly, by using the compiler's -MT<FILE> option.
* Makefile (%.d: %.cc): With the prior use of Makefile-ifdef'd
sed, when building on MacOS with gnu sed, every run of this rule
would fail with a sed usage error.  Also list each .d file as a
dependent.

Test Plan:
  Ensure that a selected .d file is the same as before both with
  g++ and with clang++.  However, note that the new .d files each
  contain a new reference to the .d file itself.

Reviewers: sdong, ljin, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33369

Summary:
It would be good to assing background job their IDs. Two benefits:
1) makes LOGs more readable
2) I might use it in my EventLogger, which will try to make our LOG easier to read/query/visualize

Test Plan: ran rocksdb, read the LOG

Reviewers: sdong, rven, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D31617

[RocksJava] FlushOptions Correction

SetWaitForFlush did not set flush properly.

Summary: rockuse more memory that asked to. Monitor and report.

Test Plan: run the pro with conditions to simulate the overusage. It should report that the process is using more memory than needed.

Reviewers: yhchiang, rven, sdong, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33249

Summary: DBTest.DestroyDBMetaDatabase occasionally fails on my dev host, for file not existing. Always create directories to avoid that.

Test Plan: Run the test

Reviewers: rven, yhchiang, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33321

Summary: Remember whole key or prefix filtering on/off in SST files. If user opens the DB with a different setting that cannot be satisfied while reading the SST file, ignore the bloom filter.

Test Plan: Add a unit test for it

Reviewers: yhchiang, igor, rven

Reviewed By: rven

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D32889

modify double type equal check in json_document.cc