2 changed files with 598 additions and 59 deletions
--- a/doc/developer-notes.md
+++ b/doc/developer-notes.md
@ -1,39 +1,116 @@
 Developer Notes
 ===============
 <!-- markdown-toc start -->
 **Table of Contents**
 - [Developer Notes](#developer-notes)
    - [Coding Style](#coding-style)
    - [Doxygen comments](#doxygen-comments)
    - [Development tips and tricks](#development-tips-and-tricks)
        - [Compiling for debugging](#compiling-for-debugging)
        - [Compiling for gprof profiling](#compiling-for-gprof-profiling)
        - [debug.log](#debuglog)
        - [Testnet and Regtest modes](#testnet-and-regtest-modes)
        - [DEBUG_LOCKORDER](#debug_lockorder)
        - [Valgrind suppressions file](#valgrind-suppressions-file)
        - [Compiling for test coverage](#compiling-for-test-coverage)
    - [Locking/mutex usage notes](#lockingmutex-usage-notes)
    - [Threads](#threads)
    - [Ignoring IDE/editor files](#ignoring-ideeditor-files)
 - [Development guidelines](#development-guidelines)
    - [General Bitcoin Core](#general-bitcoin-core)
    - [Wallet](#wallet)
    - [General C++](#general-c)
    - [C++ data structures](#c-data-structures)
    - [Strings and formatting](#strings-and-formatting)
    - [Variable names](#variable-names)
    - [Threads and synchronization](#threads-and-synchronization)
    - [Source code organization](#source-code-organization)
    - [GUI](#gui)
    - [Subtrees](#subtrees)
    - [Git and GitHub tips](#git-and-github-tips)
    - [Scripted diffs](#scripted-diffs)
    - [RPC interface guidelines](#rpc-interface-guidelines)
 <!-- markdown-toc end -->
 Coding Style
 ---------------
 Various coding styles have been used during the history of the codebase,
 and the result is not very consistent. However, we're now trying to converge to
-a single style, so please use it in new code. Old code will be converted
+a single style, which is specified below. When writing patches, favor the new
-gradually.
+style over attempting to mimic the surrounding style, except for move-only
- Basic rules specified in src/.clang-format. Use a recent clang-format-3.5 to format automatically.
+commits.
-  - Braces on new lines for namespaces, classes, functions, methods.
+
 Do not submit patches solely to modify the style of existing code.
 - **Indentation and whitespace rules** as specified in
 [src/.clang-format](/src/.clang-format). You can use the provided
 [clang-format-diff script](/contrib/devtools/README.md#clang-format-diffpy)
 tool to clean up patches automatically before submission.
  - Braces on new lines for classes, functions, methods.
  - Braces on the same line for everything else.
  - 4 space indentation (no tabs) for every block except namespaces.
-  - No indentation for public/protected/private or for namespaces.
+  - No indentation for `public`/`protected`/`private` or for `namespace`.
  - No extra spaces inside parenthesis; don't do ( this )
-  - No space after function names; one space after if, for and while.
+  - No space after function names; one space after `if`, `for` and `while`.
  - If an `if` only has a single-statement `then`-clause, it can appear
    on the same line as the `if`, without braces. In every other case,
    braces are required, and the `then` and `else` clauses must appear
    correctly indented on a new line.
 - **Symbol naming conventions**. These are preferred in new code, but are not
 required when doing so would need changes to significant pieces of existing
 code.
  - Variable and namespace names are all lowercase, and may use `_` to
    separate words (snake_case).
    - Class member variables have a `m_` prefix.
    - Global variables have a `g_` prefix.
  - Constant names are all uppercase, and use `_` to separate words.
  - Class names, function names and method names are UpperCamelCase
    (PascalCase). Do not prefix class names with `C`.
  - Test suite naming convention: The Boost test suite in file
    `src/test/foo_tests.cpp` should be named `foo_tests`. Test suite names
    must be unique.
 - **Miscellaneous**
  - `++i` is preferred over `i++`.
  - `nullptr` is preferred over `NULL` or `(void*)0`.
  - `static_assert` is preferred over `assert` where possible. Generally; compile-time checking is preferred over run-time checking.
  - `enum class` is preferred over `enum` where possible. Scoped enumerations avoid two potential pitfalls/problems with traditional C++ enumerations: implicit conversions to int, and name clashes due to enumerators being exported to the surrounding scope.
 Block style example:
 ```c++
-namespace foo
+int g_count = 0;
-{
+
 namespace foo {
 class Class
 {
-    bool Function(char* psz, int n)
+    std::string m_name;
 public:
    bool Function(const std::string& s, int n)
    {
        // Comment summarising what this section of code does
-        for (int i = 0; i < n; i++) {
+        for (int i = 0; i < n; ++i) {
            int total_sum = 0;
            // When something fails, return early
-            if (!Something())
+            if (!Something()) return false;
                return false;
            ...
            if (SomethingElse(i)) {
                total_sum += ComputeSomething(g_count);
            } else {
                DoSomething(m_name, total_sum);
            }
        }
        // Success return is usually at the end
        return true;
    }
 }
-}
+} // namespace foo
 ```
 Doxygen comments
@ -95,57 +172,146 @@ Not OK (used plenty in the current source, but not picked up):
 A full list of comment syntaxes picked up by doxygen can be found at http://www.stack.nl/~dimitri/doxygen/manual/docblocks.html,
 but if possible use one of the above styles.
 Documentation can be generated with `make docs` and cleaned up with `make clean-docs`.
 Development tips and tricks
 ---------------------------
-**compiling for debugging**
+### Compiling for debugging
-Run configure with the --enable-debug option, then make. Or run configure with
+Run configure with `--enable-debug` to add additional compiler flags that
-CXXFLAGS="-g -ggdb -O0" or whatever debug flags you need.
+produce better debugging builds.
-**debug.log**
+### Compiling for gprof profiling
 Run configure with the `--enable-gprof` option, then make.
 ### debug.log
 If the code is behaving strangely, take a look in the debug.log file in the data directory;
 error and debugging messages are written there.
-The -debug=... command-line option controls debugging; running with just -debug or -debug=1 will turn
+The `-debug=...` command-line option controls debugging; running with just `-debug` or `-debug=1` will turn
 on all categories (and give you a very large debug.log file).
-The Qt code routes qDebug() output to debug.log under category "qt": run with -debug=qt
+The Qt code routes `qDebug()` output to debug.log under category "qt": run with `-debug=qt`
 to see it.
-**testnet and regtest modes**
+### Testnet and Regtest modes
-Run with the -testnet option to run with "play bitcoins" on the test network, if you
+Run with the `-testnet` option to run with "play bitcoins" on the test network, if you
 are testing multi-machine code that needs to operate across the internet.
-If you are testing something that can run on one machine, run with the -regtest option.
+If you are testing something that can run on one machine, run with the `-regtest` option.
-In regression test mode, blocks can be created on-demand; see qa/rpc-tests/ for tests
+In regression test mode, blocks can be created on-demand; see [test/functional/](/test/functional) for tests
-that run in -regtest mode.
+that run in `-regtest` mode.
-**DEBUG_LOCKORDER**
+### DEBUG_LOCKORDER
-Bitcoin Core is a multithreaded application, and deadlocks or other multithreading bugs
+Bitcoin Core is a multi-threaded application, and deadlocks or other
-can be very difficult to track down. Compiling with -DDEBUG_LOCKORDER (configure
+multi-threading bugs can be very difficult to track down. The `--enable-debug`
-CXXFLAGS="-DDEBUG_LOCKORDER -g") inserts run-time checks to keep track of which locks
+configure option adds `-DDEBUG_LOCKORDER` to the compiler flags. This inserts
-are held, and adds warnings to the debug.log file if inconsistencies are detected.
+run-time checks to keep track of which locks are held, and adds warnings to the
 debug.log file if inconsistencies are detected.
 ### Valgrind suppressions file
 Valgrind is a programming tool for memory debugging, memory leak detection, and
 profiling. The repo contains a Valgrind suppressions file
 ([`valgrind.supp`](https://github.com/bitcoin/bitcoin/blob/master/contrib/valgrind.supp))
 which includes known Valgrind warnings in our dependencies that cannot be fixed
 in-tree. Example use:
 ```shell
 $ valgrind --suppressions=contrib/valgrind.supp src/test/test_bitcoin
 $ valgrind --suppressions=contrib/valgrind.supp --leak-check=full \
      --show-leak-kinds=all src/test/test_bitcoin --log_level=test_suite
 $ valgrind -v --leak-check=full src/bitcoind -printtoconsole
 ```
 ### Compiling for test coverage
 LCOV can be used to generate a test coverage report based upon `make check`
 execution. LCOV must be installed on your system (e.g. the `lcov` package
 on Debian/Ubuntu).
 To enable LCOV report generation during test runs:
 ```shell
 ./configure --enable-lcov
 make
 make cov
 # A coverage report will now be accessible at `./test_bitcoin.coverage/index.html`.
 ```
 **Sanitizers**
 Bitcoin can be compiled with various "sanitizers" enabled, which add
 instrumentation for issues regarding things like memory safety, thread race
 conditions, or undefined behavior. This is controlled with the
 `--with-sanitizers` configure flag, which should be a comma separated list of
 sanitizers to enable. The sanitizer list should correspond to supported
 `-fsanitize=` options in your compiler. These sanitizers have runtime overhead,
 so they are most useful when testing changes or producing debugging builds.
 Some examples:
 ```bash
 # Enable both the address sanitizer and the undefined behavior sanitizer
 ./configure --with-sanitizers=address,undefined
 # Enable the thread sanitizer
 ./configure --with-sanitizers=thread
 ```
 If you are compiling with GCC you will typically need to install corresponding
 "san" libraries to actually compile with these flags, e.g. libasan for the
 address sanitizer, libtsan for the thread sanitizer, and libubsan for the
 undefined sanitizer. If you are missing required libraries, the configure script
 will fail with a linker error when testing the sanitizer flags.
 The test suite should pass cleanly with the `thread` and `undefined` sanitizers,
 but there are a number of known problems when using the `address` sanitizer. The
 address sanitizer is known to fail in
 [sha256_sse4::Transform](/src/crypto/sha256_sse4.cpp) which makes it unusable
 unless you also use `--disable-asm` when running configure. We would like to fix
 sanitizer issues, so please send pull requests if you can fix any errors found
 by the address sanitizer (or any other sanitizer).
 Not all sanitizer options can be enabled at the same time, e.g. trying to build
 with `--with-sanitizers=address,thread` will fail in the configure script as
 these sanitizers are mutually incompatible. Refer to your compiler manual to
 learn more about these options and which sanitizers are supported by your
 compiler.
 Additional resources:
 * [AddressSanitizer](https://clang.llvm.org/docs/AddressSanitizer.html)
 * [LeakSanitizer](https://clang.llvm.org/docs/LeakSanitizer.html)
 * [MemorySanitizer](https://clang.llvm.org/docs/MemorySanitizer.html)
 * [ThreadSanitizer](https://clang.llvm.org/docs/ThreadSanitizer.html)
 * [UndefinedBehaviorSanitizer](https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html)
 * [GCC Instrumentation Options](https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html)
 * [Google Sanitizers Wiki](https://github.com/google/sanitizers/wiki)
 * [Issue #12691: Enable -fsanitize flags in Travis](https://github.com/bitcoin/bitcoin/issues/12691)
 Locking/mutex usage notes
 -------------------------
 The code is multi-threaded, and uses mutexes and the
-LOCK/TRY_LOCK macros to protect data structures.
+`LOCK` and `TRY_LOCK` macros to protect data structures.
-Deadlocks due to inconsistent lock ordering (thread 1 locks cs_main
+Deadlocks due to inconsistent lock ordering (thread 1 locks `cs_main` and then
-and then cs_wallet, while thread 2 locks them in the opposite order:
+`cs_wallet`, while thread 2 locks them in the opposite order: result, deadlock
-result, deadlock as each waits for the other to release its lock) are
+as each waits for the other to release its lock) are a problem. Compile with
-a problem. Compile with -DDEBUG_LOCKORDER to get lock order
+`-DDEBUG_LOCKORDER` (or use `--enable-debug`) to get lock order inconsistencies
-inconsistencies reported in the debug.log file.
+reported in the debug.log file.
 Re-architecting the core code so there are better-defined interfaces
 between the various components is a goal, with any necessary locking
-done by the components (e.g. see the self-contained CKeyStore class
+done by the components (e.g. see the self-contained `CBasicKeyStore` class
-and its cs_KeyStore lock for example).
+and its `cs_KeyStore` lock for example).
 Threads
 -------
@ -170,12 +336,8 @@ Threads
 - DumpAddresses : Dumps IP addresses of nodes to peers.dat.
 - ThreadFlushWalletDB : Close the wallet.dat file if it hasn't been used in 500ms.
 - ThreadRPCServer : Remote procedure call handler, listens on port 8332 for connections and services them.
 - BitcoinMiner : Generates bitcoins (if wallet is enabled).
 - Shutdown : Does an orderly shutdown of everything.
 Ignoring IDE/editor files
@ -240,7 +402,7 @@ Wallet
  - *Rationale*: In RPC code that conditionally uses the wallet (such as
    `validateaddress`) it is easy to forget that global pointer `pwalletMain`
-    can be NULL. See `qa/rpc-tests/disablewallet.py` for functional tests
+    can be nullptr. See `test/functional/disablewallet.py` for functional tests
    exercising the API with `-disablewallet`
 - Include `db_cxx.h` (BerkeleyDB header) only when `ENABLE_WALLET` is set
@ -252,7 +414,7 @@ General C++
 - Assertions should not have side-effects
-  - *Rationale*: Even though the source code is set to to refuse to compile
+  - *Rationale*: Even though the source code is set to refuse to compile
    with assertions disabled, having side-effects in assertions is unexpected and
    makes the code harder to understand
@ -263,7 +425,7 @@ General C++
      the `.h` to the `.cpp` should not result in build errors
 - Use the RAII (Resource Acquisition Is Initialization) paradigm where possible. For example by using
-  `scoped_pointer` for allocations in a function.
+  `unique_ptr` for allocations in a function.
  - *Rationale*: This avoids memory and resource leaks, and ensures exception safety
@ -282,19 +444,33 @@ C++ data structures
  - *Rationale*: Behavior is undefined. In C++ parlor this means "may reformat
    the universe", in practice this has resulted in at least one hard-to-debug crash bug
- Watch out for vector out-of-bounds exceptions. `&vch[0]` is illegal for an
+- Watch out for out-of-bounds vector access. `&vch[vch.size()]` is illegal,
-  empty vector, `&vch[vch.size()]` is always illegal. Use `begin_ptr(vch)` and
+  including `&vch[0]` for an empty vector. Use `vch.data()` and `vch.data() +
-  `end_ptr(vch)` to get the begin and end pointer instead (defined in
+  vch.size()` instead.
  `serialize.h`)
 - Vector bounds checking is only enabled in debug mode. Do not rely on it
- Make sure that constructors initialize all fields. If this is skipped for a
+- Initialize all non-static class members where they are defined.
-  good reason (i.e., optimization on the critical path), add an explicit
+  If this is skipped for a good reason (i.e., optimization on the critical
-  comment about this
+  path), add an explicit comment about this
  - *Rationale*: Ensure determinism by avoiding accidental use of uninitialized
    values. Also, static analyzers balk about this.
    Initializing the members in the declaration makes it easy to
    spot uninitialized ones.
 ```cpp
 class A
 {
    uint32_t m_count{0};
 }
 ```
 - By default, declare single-argument constructors `explicit`.
  - *Rationale*: This is a precaution to avoid unintended conversions that might
    arise when single-argument constructors are used as implicit conversion
    functions.
 - Use explicitly signed or unsigned `char`s, or even better `uint8_t` and
  `int8_t`. Do not use bare `char` unless it is to pass to a third-party API.
@ -321,14 +497,67 @@ Strings and formatting
    buffer overflows and surprises with `\0` characters. Also some C string manipulations
    tend to act differently depending on platform, or even the user locale
- Use `ParseInt32`, `ParseInt64`, `ParseDouble` from `utilstrencodings.h` for number parsing
+- Use `ParseInt32`, `ParseInt64`, `ParseUInt32`, `ParseUInt64`, `ParseDouble` from `utilstrencodings.h` for number parsing
-  - *Rationale*: These functions do overflow checking, and avoid pesky locale issues
+  - *Rationale*: These functions do overflow checking, and avoid pesky locale issues.
 - Avoid using locale dependent functions if possible. You can use the provided
  [`lint-locale-dependence.sh`](/contrib/devtools/lint-locale-dependence.sh)
  to check for accidental use of locale dependent functions.
  - *Rationale*: Unnecessary locale dependence can cause bugs that are very tricky to isolate and fix.
  - These functions are known to be locale dependent:
    `alphasort`, `asctime`, `asprintf`, `atof`, `atoi`, `atol`, `atoll`, `atoq`,
    `btowc`, `ctime`, `dprintf`, `fgetwc`, `fgetws`, `fprintf`, `fputwc`,
    `fputws`, `fscanf`, `fwprintf`, `getdate`, `getwc`, `getwchar`, `isalnum`,
    `isalpha`, `isblank`, `iscntrl`, `isdigit`, `isgraph`, `islower`, `isprint`,
    `ispunct`, `isspace`, `isupper`, `iswalnum`, `iswalpha`, `iswblank`,
    `iswcntrl`, `iswctype`, `iswdigit`, `iswgraph`, `iswlower`, `iswprint`,
    `iswpunct`, `iswspace`, `iswupper`, `iswxdigit`, `isxdigit`, `mblen`,
    `mbrlen`, `mbrtowc`, `mbsinit`, `mbsnrtowcs`, `mbsrtowcs`, `mbstowcs`,
    `mbtowc`, `mktime`, `putwc`, `putwchar`, `scanf`, `snprintf`, `sprintf`,
    `sscanf`, `stoi`, `stol`, `stoll`, `strcasecmp`, `strcasestr`, `strcoll`,
    `strfmon`, `strftime`, `strncasecmp`, `strptime`, `strtod`, `strtof`,
    `strtoimax`, `strtol`, `strtold`, `strtoll`, `strtoq`, `strtoul`,
    `strtoull`, `strtoumax`, `strtouq`, `strxfrm`, `swprintf`, `tolower`,
    `toupper`, `towctrans`, `towlower`, `towupper`, `ungetwc`, `vasprintf`,
    `vdprintf`, `versionsort`, `vfprintf`, `vfscanf`, `vfwprintf`, `vprintf`,
    `vscanf`, `vsnprintf`, `vsprintf`, `vsscanf`, `vswprintf`, `vwprintf`,
    `wcrtomb`, `wcscasecmp`, `wcscoll`, `wcsftime`, `wcsncasecmp`, `wcsnrtombs`,
    `wcsrtombs`, `wcstod`, `wcstof`, `wcstoimax`, `wcstol`, `wcstold`,
    `wcstoll`, `wcstombs`, `wcstoul`, `wcstoull`, `wcstoumax`, `wcswidth`,
    `wcsxfrm`, `wctob`, `wctomb`, `wctrans`, `wctype`, `wcwidth`, `wprintf`
 - For `strprintf`, `LogPrint`, `LogPrintf` formatting characters don't need size specifiers
  - *Rationale*: Bitcoin Core uses tinyformat, which is type safe. Leave them out to avoid confusion
 Variable names
 --------------
 Although the shadowing warning (`-Wshadow`) is not enabled by default (it prevents issues rising
 from using a different variable with the same name),
 please name variables so that their names do not shadow variables defined in the source code.
 E.g. in member initializers, prepend `_` to the argument name shadowing the
 member name:
 ```c++
 class AddressBookPage
 {
    Mode m_mode;
 }
 AddressBookPage::AddressBookPage(Mode _mode) :
      m_mode(_mode)
 ...
 ```
 When using nested cycles, do not name the inner cycle variable the same as in
 upper cycle etc.
 Threads and synchronization
 ----------------------------
@ -366,11 +595,57 @@ Source code organization
  - *Rationale*: Shorter and simpler header files are easier to read, and reduce compile time
 - Use only the lowercase alphanumerics (`a-z0-9`), underscore (`_`) and hyphen (`-`) in source code filenames.
  - *Rationale*: `grep`:ing and auto-completing filenames is easier when using a consistent
    naming pattern. Potential problems when building on case-insensitive filesystems are
    avoided when using only lowercase characters in source code filenames.
 - Every `.cpp` and `.h` file should `#include` every header file it directly uses classes, functions or other
  definitions from, even if those headers are already included indirectly through other headers.
  - *Rationale*: Excluding headers because they are already indirectly included results in compilation
    failures when those indirect dependencies change. Furthermore, it obscures what the real code
    dependencies are.
 - Don't import anything into the global namespace (`using namespace ...`). Use
  fully specified types such as `std::string`.
  - *Rationale*: Avoids symbol conflicts
 - Terminate namespaces with a comment (`// namespace mynamespace`). The comment
  should be placed on the same line as the brace closing the namespace, e.g.
 ```c++
 namespace mynamespace {
 ...
 } // namespace mynamespace
 namespace {
 ...
 } // namespace
 ```
  - *Rationale*: Avoids confusion about the namespace context
 - Use `#include <primitives/transaction.h>` bracket syntax instead of
  `#include "primitives/transactions.h"` quote syntax.
  - *Rationale*: Bracket syntax is less ambiguous because the preprocessor
    searches a fixed list of include directories without taking location of the
    source file into account. This allows quoted includes to stand out more when
    the location of the source file actually is relevant.
 - Use include guards to avoid the problem of double inclusion. The header file
  `foo/bar.h` should use the include guard identifier `BITCOIN_FOO_BAR_H`, e.g.
 ```c++
 #ifndef BITCOIN_FOO_BAR_H
 #define BITCOIN_FOO_BAR_H
 ...
 #endif // BITCOIN_FOO_BAR_H
 ```
 GUI
 -----
@ -379,3 +654,265 @@ GUI
  - *Rationale*: Model classes pass through events and data from the core, they
    should not interact with the user. That's where View classes come in. The converse also
    holds: try to not directly access core data structures from Views.
 - Avoid adding slow or blocking code in the GUI thread. In particular do not
  add new `interfaces::Node` and `interfaces::Wallet` method calls, even if they
  may be fast now, in case they are changed to lock or communicate across
  processes in the future.
  Prefer to offload work from the GUI thread to worker threads (see
  `RPCExecutor` in console code as an example) or take other steps (see
  https://doc.qt.io/archives/qq/qq27-responsive-guis.html) to keep the GUI
  responsive.
  - *Rationale*: Blocking the GUI thread can increase latency, and lead to
    hangs and deadlocks.
 Subtrees
 ----------
 Several parts of the repository are subtrees of software maintained elsewhere.
 Some of these are maintained by active developers of Bitcoin Core, in which case changes should probably go
 directly upstream without being PRed directly against the project.  They will be merged back in the next
 subtree merge.
 Others are external projects without a tight relationship with our project.  Changes to these should also
 be sent upstream but bugfixes may also be prudent to PR against Bitcoin Core so that they can be integrated
 quickly.  Cosmetic changes should be purely taken upstream.
 There is a tool in `test/lint/git-subtree-check.sh` to check a subtree directory for consistency with
 its upstream repository.
 Current subtrees include:
 - src/leveldb
  - Upstream at https://github.com/google/leveldb ; Maintained by Google, but
    open important PRs to Core to avoid delay.
  - **Note**: Follow the instructions in [Upgrading LevelDB](#upgrading-leveldb) when
    merging upstream changes to the leveldb subtree.
 - src/libsecp256k1
  - Upstream at https://github.com/bitcoin-core/secp256k1/ ; actively maintaned by Core contributors.
 - src/crypto/ctaes
  - Upstream at https://github.com/bitcoin-core/ctaes ; actively maintained by Core contributors.
 - src/univalue
  - Upstream at https://github.com/jgarzik/univalue ; report important PRs to Core to avoid delay.
 Upgrading LevelDB
 ---------------------
 Extra care must be taken when upgrading LevelDB. This section explains issues
 you must be aware of.
 ### File Descriptor Counts
 In most configurations we use the default LevelDB value for `max_open_files`,
 which is 1000 at the time of this writing. If LevelDB actually uses this many
 file descriptors it will cause problems with Bitcoin's `select()` loop, because
 it may cause new sockets to be created where the fd value is >= 1024. For this
 reason, on 64-bit Unix systems we rely on an internal LevelDB optimization that
 uses `mmap()` + `close()` to open table files without actually retaining
 references to the table file descriptors. If you are upgrading LevelDB, you must
 sanity check the changes to make sure that this assumption remains valid.
 In addition to reviewing the upstream changes in `env_posix.cc`, you can use `lsof` to
 check this. For example, on Linux this command will show open `.ldb` file counts:
 ```bash
 $ lsof -p $(pidof bitcoind) |\
    awk 'BEGIN { fd=0; mem=0; } /ldb$/ { if ($4 == "mem") mem++; else fd++ } END { printf "mem = %s, fd = %s\n", mem, fd}'
 mem = 119, fd = 0
 ```
 The `mem` value shows how many files are mmap'ed, and the `fd` value shows you
 many file descriptors these files are using. You should check that `fd` is a
 small number (usually 0 on 64-bit hosts).
 See the notes in the `SetMaxOpenFiles()` function in `dbwrapper.cc` for more
 details.
 ### Consensus Compatibility
 It is possible for LevelDB changes to inadvertently change consensus
 compatibility between nodes. This happened in Bitcoin 0.8 (when LevelDB was
 first introduced). When upgrading LevelDB you should review the upstream changes
 to check for issues affecting consensus compatibility.
 For example, if LevelDB had a bug that accidentally prevented a key from being
 returned in an edge case, and that bug was fixed upstream, the bug "fix" would
 be an incompatible consensus change. In this situation the correct behavior
 would be to revert the upstream fix before applying the updates to Bitcoin's
 copy of LevelDB. In general you should be wary of any upstream changes affecting
 what data is returned from LevelDB queries.
 Git and GitHub tips
 ---------------------
 - For resolving merge/rebase conflicts, it can be useful to enable diff3 style using
  `git config merge.conflictstyle diff3`. Instead of
        <<<
        yours
        ===
        theirs
        >>>
  you will see
        <<<
        yours
        |||
        original
        ===
        theirs
        >>>
  This may make it much clearer what caused the conflict. In this style, you can often just look
  at what changed between *original* and *theirs*, and mechanically apply that to *yours* (or the other way around).
 - When reviewing patches which change indentation in C++ files, use `git diff -w` and `git show -w`. This makes
  the diff algorithm ignore whitespace changes. This feature is also available on github.com, by adding `?w=1`
  at the end of any URL which shows a diff.
 - When reviewing patches that change symbol names in many places, use `git diff --word-diff`. This will instead
  of showing the patch as deleted/added *lines*, show deleted/added *words*.
 - When reviewing patches that move code around, try using
  `git diff --patience commit~:old/file.cpp commit:new/file/name.cpp`, and ignoring everything except the
  moved body of code which should show up as neither `+` or `-` lines. In case it was not a pure move, this may
  even work when combined with the `-w` or `--word-diff` options described above.
 - When looking at other's pull requests, it may make sense to add the following section to your `.git/config`
  file:
        [remote "upstream-pull"]
                fetch = +refs/pull/*:refs/remotes/upstream-pull/*
                url = git@github.com:bitcoin/bitcoin.git
  This will add an `upstream-pull` remote to your git repository, which can be fetched using `git fetch --all`
  or `git fetch upstream-pull`. Afterwards, you can use `upstream-pull/NUMBER/head` in arguments to `git show`,
  `git checkout` and anywhere a commit id would be acceptable to see the changes from pull request NUMBER.
 Scripted diffs
 --------------
 For reformatting and refactoring commits where the changes can be easily automated using a bash script, we use
 scripted-diff commits. The bash script is included in the commit message and our Travis CI job checks that
 the result of the script is identical to the commit. This aids reviewers since they can verify that the script
 does exactly what it's supposed to do. It is also helpful for rebasing (since the same script can just be re-run
 on the new master commit).
 To create a scripted-diff:
 - start the commit message with `scripted-diff:` (and then a description of the diff on the same line)
 - in the commit message include the bash script between lines containing just the following text:
    - `-BEGIN VERIFY SCRIPT-`
    - `-END VERIFY SCRIPT-`
 The scripted-diff is verified by the tool `test/lint/commit-script-check.sh`
 Commit [`bb81e173`](https://github.com/bitcoin/bitcoin/commit/bb81e173) is an example of a scripted-diff.
 RPC interface guidelines
 --------------------------
 A few guidelines for introducing and reviewing new RPC interfaces:
 - Method naming: use consecutive lower-case names such as `getrawtransaction` and `submitblock`
  - *Rationale*: Consistency with existing interface.
 - Argument naming: use snake case `fee_delta` (and not, e.g. camel case `feeDelta`)
  - *Rationale*: Consistency with existing interface.
 - Use the JSON parser for parsing, don't manually parse integers or strings from
  arguments unless absolutely necessary.
  - *Rationale*: Introduces hand-rolled string manipulation code at both the caller and callee sites,
    which is error prone, and it is easy to get things such as escaping wrong.
    JSON already supports nested data structures, no need to re-invent the wheel.
  - *Exception*: AmountFromValue can parse amounts as string. This was introduced because many JSON
    parsers and formatters hard-code handling decimal numbers as floating point
    values, resulting in potential loss of precision. This is unacceptable for
    monetary values. **Always** use `AmountFromValue` and `ValueFromAmount` when
    inputting or outputting monetary values. The only exceptions to this are
    `prioritisetransaction` and `getblocktemplate` because their interface
    is specified as-is in BIP22.
 - Missing arguments and 'null' should be treated the same: as default values. If there is no
  default value, both cases should fail in the same way. The easiest way to follow this
  guideline is detect unspecified arguments with `params[x].isNull()` instead of
  `params.size() <= x`. The former returns true if the argument is either null or missing,
  while the latter returns true if is missing, and false if it is null.
  - *Rationale*: Avoids surprises when switching to name-based arguments. Missing name-based arguments
  are passed as 'null'.
 - Try not to overload methods on argument type. E.g. don't make `getblock(true)` and `getblock("hash")`
  do different things.
  - *Rationale*: This is impossible to use with `bitcoin-cli`, and can be surprising to users.
  - *Exception*: Some RPC calls can take both an `int` and `bool`, most notably when a bool was switched
    to a multi-value, or due to other historical reasons. **Always** have false map to 0 and
    true to 1 in this case.
 - Don't forget to fill in the argument names correctly in the RPC command table.
  - *Rationale*: If not, the call can not be used with name-based arguments.
 - Set okSafeMode in the RPC command table to a sensible value: safe mode is when the
  blockchain is regarded to be in a confused state, and the client deems it unsafe to
  do anything irreversible such as send. Anything that just queries should be permitted.
  - *Rationale*: Troubleshooting a node in safe mode is difficult if half the
    RPCs don't work.
 - Add every non-string RPC argument `(method, idx, name)` to the table `vRPCConvertParams` in `rpc/client.cpp`.
  - *Rationale*: `bitcoin-cli` and the GUI debug console use this table to determine how to
    convert a plaintext command line to JSON. If the types don't match, the method can be unusable
    from there.
 - A RPC method must either be a wallet method or a non-wallet method. Do not
  introduce new methods such as `signrawtransaction` that differ in behavior
  based on presence of a wallet.
  - *Rationale*: as well as complicating the implementation and interfering
    with the introduction of multi-wallet, wallet and non-wallet code should be
    separated to avoid introducing circular dependencies between code units.
 - Try to make the RPC response a JSON object.
  - *Rationale*: If a RPC response is not a JSON object then it is harder to avoid API breakage if
    new data in the response is needed.
 - Wallet RPCs call BlockUntilSyncedToCurrentChain to maintain consistency with
  `getblockchaininfo`'s state immediately prior to the call's execution. Wallet
  RPCs whose behavior does *not* depend on the current chainstate may omit this
  call.
  - *Rationale*: In previous versions of Bitcoin Core, the wallet was always
    in-sync with the chainstate (by virtue of them all being updated in the
    same cs_main lock). In order to maintain the behavior that wallet RPCs
    return results as of at least the highest best-known block an RPC
    client may be aware of prior to entering a wallet RPC call, we must block
    until the wallet is caught up to the chainstate as of the RPC call's entry.
    This also makes the API much easier for RPC clients to reason about.
 - Be aware of RPC method aliases and generally avoid registering the same
  callback function pointer for different RPCs.
  - *Rationale*: RPC methods registered with the same function pointer will be
    considered aliases and only the first method name will show up in the
    `help` rpc command list.
  - *Exception*: Using RPC method aliases may be appropriate in cases where a
    new RPC is replacing a deprecated RPC, to avoid both RPCs confusingly
    showing up in the command list.
--- a/src/.clang-format
+++ b/src/.clang-format
@ -6,13 +6,16 @@ AlignTrailingComments: true
 AllowAllParametersOfDeclarationOnNextLine: false
 AllowShortBlocksOnASingleLine: false
 AllowShortFunctionsOnASingleLine: All
-AllowShortIfStatementsOnASingleLine: false
+AllowShortIfStatementsOnASingleLine: true
 AllowShortLoopsOnASingleLine: false
 AlwaysBreakBeforeMultilineStrings: false
 AlwaysBreakTemplateDeclarations: true
 BinPackParameters: false
 BreakBeforeBinaryOperators: false
-BreakBeforeBraces: Linux
+BreakBeforeBraces: Custom
 BraceWrapping:
  AfterClass: true
  AfterFunction: true
 BreakBeforeTernaryOperators: false
 BreakConstructorInitializersBeforeComma: false
 ColumnLimit:     0
@ -23,7 +26,6 @@ ContinuationIndentWidth: 4
 Cpp11BracedListStyle: true
 DerivePointerAlignment: false
 DisableFormat:   false
 ForEachMacros:   [ foreach, Q_FOREACH, BOOST_FOREACH, BOOST_REVERSE_FOREACH ]
 IndentCaseLabels: false
 IndentFunctionDeclarationAfterType: false
 IndentWidth:     4