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README.md

42

Copyright (c) 2014-2018 The Monero Project. Copyright (c) 2018-2019 The 42 Project. Portions Copyright (c) 2012-2013 The Cryptonote developers.

Development resources

Vulnerability response

Announcements/News

Introduction

42 is a private, cryptographically secured, untraceable, decentralised digital currency that is easy to use and completely anonymous. No one, including governments, and not even Bill Murray can make transactions on your wallet. Except you of course! 42 is based off the CryptoNote protocol and it's codebase is forked from the Monero project.

Privacy: 42 uses a cryptographically sound system to allow you to send and receive funds without your transactions being easily revealed on the blockchain (the ledger of transactions that everyone has) the same way Monero does. Every transaction made on the 42 blockchain is indistinguishable from any other transactions, allowing you to have total anonymity.

Security: Using the power of a distributed peer-to-peer consensus network, every transaction on the network is cryptographically secured. Individual wallets have a 25 word mnemonic seed that is only displayed once, and can be written down to backup the wallet. Wallet files are encrypted with a passphrase to ensure they are useless if stolen.

Untraceability: By taking advantage of ring signatures, a special property of a certain type of cryptography, 42 is able to ensure that transactions are not only untraceable, but have an optional measure of ambiguity that ensures that transactions cannot easily be tied back to an individual user or computer.

About this project

This is the core implementation of 42. It is open source and completely free to use without restrictions, except for those specified in the license agreement below. There are no restrictions on anyone creating an alternative implementation of 42 that uses the protocol and network in a compatible manner. In the event that Earth is destroyed due to Galactic bureaucracy, we are not responsible for lost coins.

Anyone is welcome to contribute to 42's codebase! If you have a fix or code change, feel free to submit it as a pull request directly to the "master" branch. In cases where the change is relatively small or does not affect other parts of the codebase it may be merged in immediately by any one of the collaborators. On the other hand, if the change is particularly large or complex, it is expected that it will be discussed at length either well in advance of the pull request being submitted, or even directly on the pull request.

Supporting the project

42 is a 100% community-sponsored endeavor. If you want to help the project out, the best way would be to contribute to the codebase! Alternatively, donations can be made so we can build that restaurant I've been thinking about.

The 42 donation address is: foUrDvc6vtJYMvqpx4oydJjL445udJ83M8rAqpkF8hEcbyLCp5MhvLaLGXtVYkqVXDG8YEpGBU7F241FtWXVCFEK7EMgnjrsM8 (viewkey: 32ceccc14433c456d58ee471893f7f79db3c57f8acfd2bc607ecbe89c9606e03 )

The Monero donation address is: todo (viewkey: todo)

The Bitcoin donation address is: todo

License

See LICENSE.

Contributing

If you want to help out, see CONTRIBUTING for a set of guidelines.

Scheduled software upgrades

42 uses a fixed-schedule software upgrade (hard fork) mechanism to implement new features. This means that users of 42 (end users and service providers) should run current versions and upgrade their software on a regular schedule. As of now, we have not had any scheduled software upgrades yet. When we do, we will list dates and block heights here and various other sources.

Compiling 42 from source

Dependencies

The following table summarizes the tools and libraries required to build. A few of the libraries are also included in this repository (marked as "Vendored"). By default, the build uses the library installed on the system, and ignores the vendored sources. However, if no library is found installed on the system, then the vendored source will be built and used. The vendored sources are also used for statically-linked builds because distribution packages often include only shared library binaries (.so) but not static library archives (.a).

Dep Min. version Vendored Debian/Ubuntu pkg Arch pkg Fedora Optional Purpose
GCC 4.7.3 NO build-essential base-devel gcc NO
CMake 3.5 NO cmake cmake cmake NO
pkg-config any NO pkg-config base-devel pkgconf NO
Boost 1.58 NO libboost-all-dev boost boost-devel NO C++ libraries
OpenSSL basically any NO libssl-dev openssl openssl-devel NO sha256 sum
libzmq 3.0.0 NO libzmq3-dev zeromq cppzmq-devel NO ZeroMQ library
OpenPGM ? NO libpgm-dev libpgm openpgm-devel NO For ZeroMQ
libnorm[2] ? NO libnorm-dev ` YES For ZeroMQ
libunbound 1.4.16 YES libunbound-dev unbound unbound-devel NO DNS resolver
libsodium ? NO libsodium-dev libsodium libsodium-devel NO cryptography
libunwind any NO libunwind8-dev libunwind libunwind-devel YES Stack traces
liblzma any NO liblzma-dev xz xz-devel YES For libunwind
libreadline 6.3.0 NO libreadline6-dev readline readline-devel YES Input editing
ldns 1.6.17 NO libldns-dev ldns ldns-devel YES SSL toolkit
expat 1.1 NO libexpat1-dev expat expat-devel YES XML parsing
GTest 1.5 YES libgtest-dev[1] gtest gtest-devel YES Test suite
Doxygen any NO doxygen doxygen doxygen YES Documentation
Graphviz any NO graphviz graphviz graphviz YES Documentation

[1] On Debian/Ubuntu libgtest-dev only includes sources and headers. You must build the library binary manually. This can be done with the following command sudo apt-get install libgtest-dev && cd /usr/src/gtest && sudo cmake . && sudo make && sudo mv libg* /usr/lib/ [2] libnorm-dev is needed if your zmq library was built with libnorm, and not needed otherwise

Debian / Ubuntu one liner for all dependencies
sudo apt update && sudo apt install build-essential cmake pkg-config libboost-all-dev libssl-dev libzmq3-dev libunbound-dev libsodium-dev libunwind8-dev liblzma-dev libreadline6-dev libldns-dev libexpat1-dev doxygen graphviz libpgm-dev

Cloning the repository

Clone recursively to pull-in needed submodule(s):

$ git clone --recursive https://github.com/FourtyTwo/42

If you already have a repo cloned, initialize and update:

$ cd 42 && git submodule init && git submodule update

Build instructions

42 uses the CMake build system and a top-level Makefile that invokes cmake commands as needed.

On Linux and OS X

  • Install the dependencies

  • Change to the root of the source code directory, update submodules, and build:

      cd 42
      git submodule update --force --init external/rapidjson external/unbound external/miniupnp external/trezor-common
      make
    

    Optional: If your machine has several cores and enough memory, enable parallel build by running make -j<number of threads> instead of make. For this to be worthwhile, the machine should have one core and about 2GB of RAM available per thread.

    Note: If cmake can not find zmq.hpp file on OS X, installing zmq.hpp from https://github.com/zeromq/cppzmq to /usr/local/include should fix that error.

  • The resulting executables can be found in build/release/bin

  • Add PATH="$PATH:$HOME/42/build/release/bin" to .profile

  • Run 42 with 42d --detach

  • Optional: build and run the test suite to verify the binaries:

      make release-test
    

    NOTE: core_tests test may take a few hours to complete.

  • Optional: to build binaries suitable for debugging:

       make debug
    
  • Optional: to build statically-linked binaries:

       make release-static
    

Dependencies need to be built with -fPIC. Static libraries usually aren't, so you may have to build them yourself with -fPIC. Refer to their documentation for how to build them.

  • Optional: build documentation in doc/html (omit HAVE_DOT=YES if graphviz is not installed):

      HAVE_DOT=YES doxygen Doxyfile
    

On the Raspberry Pi

Tested on a Raspberry Pi Zero with a clean install of minimal Raspbian Stretch (2017-09-07 or later) from https://www.raspberrypi.org/downloads/raspbian/. If you are using Raspian Jessie, please see note in the following section.

  • apt-get update && apt-get upgrade to install all of the latest software

  • Install the dependencies for 42 from the 'Debian' column in the table above.

  • Increase the system swap size:

	sudo /etc/init.d/dphys-swapfile stop  
	sudo nano /etc/dphys-swapfile  
	CONF_SWAPSIZE=1024  
	sudo /etc/init.d/dphys-swapfile start  
  • If using an external hard disk without an external power supply, ensure it gets enough power to avoid hardware issues when syncing, by adding the line "max_usb_current=1" to /boot/config.txt

  • Clone 42 and checkout most recent release version:

        git clone https://github.com/FourtyTwo/42.git
	cd 42
	git submodule update --force --init external/rapidjson external/miniupnp external/unbound external/trezor-common
  • Build:
        make release
  • Wait 4-6 hours

  • The resulting executables can be found in build/release/bin

  • Add PATH="$PATH:$HOME/42/build/release/bin" to .profile

  • Run 42 with 42d --detach

  • You may wish to reduce the size of the swap file after the build has finished, and delete the boost directory from your home directory

Note for Raspbian Jessie users:

If you are using the older Raspbian Jessie image, compiling 42 is a bit more complicated. The version of Boost available in the Debian Jessie repositories is too old to use with 42, and thus you must compile a newer version yourself. The following explains the extra steps, and has been tested on a Raspberry Pi 2 with a clean install of minimal Raspbian Jessie.

  • As before, apt-get update && apt-get upgrade to install all of the latest software, and increase the system swap size
	sudo /etc/init.d/dphys-swapfile stop  
	sudo nano /etc/dphys-swapfile  
	CONF_SWAPSIZE=1024  
	sudo /etc/init.d/dphys-swapfile start  
  • Then, install the dependencies for 42 except libunwind and libboost-all-dev

  • Install the latest version of boost (this may first require invoking apt-get remove --purge libboost* to remove a previous version if you're not using a clean install):

	cd  
	wget https://sourceforge.net/projects/boost/files/boost/1.64.0/boost_1_64_0.tar.bz2  
	tar xvfo boost_1_64_0.tar.bz2  
	cd boost_1_64_0  
	./bootstrap.sh  
	sudo ./b2  
  • Wait ~8 hours
	sudo ./bjam cxxflags=-fPIC cflags=-fPIC -a install

On Windows:

Binaries for Windows are built on Windows using the MinGW toolchain within MSYS2 environment. The MSYS2 environment emulates a POSIX system. The toolchain runs within the environment and cross-compiles binaries that can run outside of the environment as a regular Windows application.

Preparing the build environment

  • Download and install the MSYS2 installer, either the 64-bit or the 32-bit package, depending on your system.

  • Open the MSYS shell via the MSYS2 Shell shortcut

  • Update packages using pacman:

      pacman -Syuu  
    
  • Exit the MSYS shell using Alt+F4

  • Edit the properties for the MSYS2 Shell shortcut changing "msys2_shell.bat" to "msys2_shell.cmd -mingw64" for 64-bit builds or "msys2_shell.cmd -mingw32" for 32-bit builds

  • Restart MSYS shell via modified shortcut and update packages again using pacman:

      pacman -Syuu  
    
  • Install dependencies:

    To build for 64-bit Windows:

      pacman -S mingw-w64-x86_64-toolchain make mingw-w64-x86_64-cmake mingw-w64-x86_64-boost mingw-w64-x86_64-openssl mingw-w64-x86_64-zeromq mingw-w64-x86_64-libsodium mingw-w64-x86_64-hidapi
    

    To build for 32-bit Windows:

      pacman -S mingw-w64-i686-toolchain make mingw-w64-i686-cmake mingw-w64-i686-boost mingw-w64-i686-openssl mingw-w64-i686-zeromq mingw-w64-i686-libsodium mingw-w64-i686-hidapi
    
  • Open the MingW shell via MinGW-w64-Win64 Shell shortcut on 64-bit Windows or MinGW-w64-Win64 Shell shortcut on 32-bit Windows. Note that if you are running 64-bit Windows, you will have both 64-bit and 32-bit MinGW shells.

Cloning

  • To git clone, run:

      git clone --recursive https://github.com/FourtyTwo/42.git
    

Building

  • Change to the cloned directory, run:

      cd 42
    
  • If you are on a 64-bit system, run:

      make release-static-win64
    
  • If you are on a 32-bit system, run:

      make release-static-win32
    
  • The resulting executables can be found in build/release/bin

  • Optional: to build Windows binaries suitable for debugging on a 64-bit system, run:

      make debug-static-win64
    
  • Optional: to build Windows binaries suitable for debugging on a 32-bit system, run:

      make debug-static-win32
    
  • The resulting executables can be found in build/debug/bin

On FreeBSD:

The project can be built from scratch by following instructions for Linux above. If you are running 42 in a jail you need to add the flag: allow.sysvipc=1 to your jail configuration, otherwise lmdb will throw the error message: Failed to open lmdb environment: Function not implemented.

We expect to add 42 into the ports tree in the near future, which will aid in managing installations using ports or packages.

On OpenBSD:

OpenBSD < 6.2

This has been tested on OpenBSD 5.8.

You will need to add a few packages to your system. pkg_add db cmake gcc gcc-libs g++ gtest.

The doxygen and graphviz packages are optional and require the xbase set.

The Boost package has a bug that will prevent librpc.a from building correctly. In order to fix this, you will have to Build boost yourself from scratch. Follow the directions here (under "Building Boost"): https://github.com/bitcoin/bitcoin/blob/master/doc/build-openbsd.md

You will have to add the serialization, date_time, and regex modules to Boost when building as they are needed by 42.

To build: env CC=egcc CXX=eg++ CPP=ecpp DEVELOPER_LOCAL_TOOLS=1 BOOST_ROOT=/path/to/the/boost/you/built make release-static-64

OpenBSD >= 6.2

You will need to add a few packages to your system. pkg_add cmake zeromq libiconv.

The doxygen and graphviz packages are optional and require the xbase set.

Build the Boost library using clang. This guide is derived from: https://github.com/bitcoin/bitcoin/blob/master/doc/build-openbsd.md

We assume you are compiling with a non-root user and you have doas enabled.

Note: do not use the boost package provided by OpenBSD, as we are installing boost to /usr/local.

# Create boost building directory
mkdir ~/boost
cd ~/boost

# Fetch boost source
ftp -o boost_1_64_0.tar.bz2 https://netcologne.dl.sourceforge.net/project/boost/boost/1.64.0/boost_1_64_0.tar.bz2 

# MUST output: (SHA256) boost_1_64_0.tar.bz2: OK
echo "7bcc5caace97baa948931d712ea5f37038dbb1c5d89b43ad4def4ed7cb683332 boost_1_64_0.tar.bz2" | sha256 -c
tar xfj boost_1_64_0.tar.bz2

# Fetch and apply boost patches, required for OpenBSD
ftp -o boost_test_impl_execution_monitor_ipp.patch https://raw.githubusercontent.com/openbsd/ports/bee9e6df517077a7269ff0dfd57995f5c6a10379/devel/boost/patches/patch-boost_test_impl_execution_monitor_ipp
ftp -o boost_config_platform_bsd_hpp.patch https://raw.githubusercontent.com/openbsd/ports/90658284fb786f5a60dd9d6e8d14500c167bdaa0/devel/boost/patches/patch-boost_config_platform_bsd_hpp

# MUST output: (SHA256) boost_config_platform_bsd_hpp.patch: OK
echo "1f5e59d1154f16ee1e0cc169395f30d5e7d22a5bd9f86358f738b0ccaea5e51d boost_config_platform_bsd_hpp.patch" | sha256 -c
# MUST output: (SHA256) boost_test_impl_execution_monitor_ipp.patch: OK
echo "30cec182a1437d40c3e0bd9a866ab5ddc1400a56185b7e671bb3782634ed0206 boost_test_impl_execution_monitor_ipp.patch" | sha256 -c

cd boost_1_64_0
patch -p0 < ../boost_test_impl_execution_monitor_ipp.patch
patch -p0 < ../boost_config_platform_bsd_hpp.patch

# Start building boost
echo 'using clang : : c++ : <cxxflags>"-fvisibility=hidden -fPIC" <linkflags>"" <archiver>"ar" <striper>"strip"  <ranlib>"ranlib" <rc>"" : ;' > user-config.jam
./bootstrap.sh --without-icu --with-libraries=chrono,filesystem,program_options,system,thread,test,date_time,regex,serialization,locale --with-toolset=clang
./b2 toolset=clang cxxflags="-stdlib=libc++" linkflags="-stdlib=libc++" -sICONV_PATH=/usr/local
doas ./b2 -d0 runtime-link=shared threadapi=pthread threading=multi link=static variant=release --layout=tagged --build-type=complete --user-config=user-config.jam -sNO_BZIP2=1 -sICONV_PATH=/usr/local --prefix=/usr/local install

Build cppzmq

Build the cppzmq bindings.

We assume you are compiling with a non-root user and you have doas enabled.

# Create cppzmq building directory
mkdir ~/cppzmq
cd ~/cppzmq

# Fetch cppzmq source
ftp -o cppzmq-4.2.3.tar.gz https://github.com/zeromq/cppzmq/archive/v4.2.3.tar.gz

# MUST output: (SHA256) cppzmq-4.2.3.tar.gz: OK
echo "3e6b57bf49115f4ae893b1ff7848ead7267013087dc7be1ab27636a97144d373 cppzmq-4.2.3.tar.gz" | sha256 -c
tar xfz cppzmq-4.2.3.tar.gz

# Start building cppzmq
cd cppzmq-4.2.3
mkdir build
cd build
cmake ..
doas make install

Build 42: env DEVELOPER_LOCAL_TOOLS=1 BOOST_ROOT=/usr/local make release-static

On Solaris:

The default Solaris linker can't be used, you have to install GNU ld, then run cmake manually with the path to your copy of GNU ld:

    mkdir -p build/release
    cd build/release
    cmake -DCMAKE_LINKER=/path/to/ld -D CMAKE_BUILD_TYPE=Release ../..
    cd ../..

Then you can run make as usual.

On Linux for Android (using docker):

    # Build image (for ARM 32-bit)
    docker build -f utils/build_scripts/android32.Dockerfile -t 42-android .
    # Build image (for ARM 64-bit)
    docker build -f utils/build_scripts/android64.Dockerfile -t 42-android .
    # Create container
    docker create -it --name 42-android 42-android bash
    # Get binaries
    docker cp 42-android:/src/build/release/bin .

Building portable statically linked binaries

By default, in either dynamically or statically linked builds, binaries target the specific host processor on which the build happens and are not portable to other processors. Portable binaries can be built using the following targets:

  • make release-static-linux-x86_64 builds binaries on Linux on x86_64 portable across POSIX systems on x86_64 processors
  • make release-static-linux-i686 builds binaries on Linux on x86_64 or i686 portable across POSIX systems on i686 processors
  • make release-static-linux-armv8 builds binaries on Linux portable across POSIX systems on armv8 processors
  • make release-static-linux-armv7 builds binaries on Linux portable across POSIX systems on armv7 processors
  • make release-static-linux-armv6 builds binaries on Linux portable across POSIX systems on armv6 processors
  • make release-static-win64 builds binaries on 64-bit Windows portable across 64-bit Windows systems
  • make release-static-win32 builds binaries on 64-bit or 32-bit Windows portable across 32-bit Windows systems

Cross Compiling

You can also cross-compile static binaries on Linux for Windows and macOS with the depends system.

  • make depends target=x86_64-linux-gnu for 64-bit linux binaries.
  • make depends target=x86_64-w64-mingw32 for 64-bit windows binaries. Requires: python3 g++-mingw-w64-x86-64 wine1.6 bc
  • make depends target=x86_64-apple-darwin11 for macOS binaries. Requires: cmake imagemagick libcap-dev librsvg2-bin libz-dev libbz2-dev libtiff-tools python-dev
  • make depends target=i686-linux-gnu for 32-bit linux binaries. Requires: g++-multilib bc
  • make depends target=i686-w64-mingw32 for 32-bit windows binaries. Requires: python3 g++-mingw-w64-i686
  • make depends target=arm-linux-gnueabihf for armv7 binaries. Requires: g++-arm-linux-gnueabihf
  • make depends target=aarch64-linux-gnu for armv8 binaries. Requires: g++-aarch64-linux-gnu

The required packages are the names for each toolchain on apt. Depending on your distro, they may have different names.

Using depends might also be easier to compile 42 on Windows than using MSYS. Activate Windows Subsystem for Linux (WSL) with a distro (for example Ubuntu), install the apt build-essentials and follow the depends steps as depicted above.

Running 42d

The build places the binary in bin/ sub-directory within the build directory from which cmake was invoked (repository root by default). To run in foreground:

./bin/42d

To list all available options, run ./bin/42d --help. Options can be specified either on the command line or in a configuration file passed by the --config-file argument. To specify an option in the configuration file, add a line with the syntax argumentname=value, where argumentname is the name of the argument without the leading dashes, for example log-level=1.

To run in background:

./bin/42d --log-file 42d.log --detach

To run as a systemd service, copy 42d.service to /etc/systemd/system/ and 42d.conf to /etc/. The example service assumes that the user 42 exists and its home is the data directory specified in the example config.

If you're on Mac, you may need to add the --max-concurrency 1 option to 42-wallet-cli, and possibly 42d, if you get crashes refreshing.

Internationalization

See README.i18n.md.

Using Tor

While 42 isn't made to integrate with Tor, it can be used wrapped with torsocks, by setting the following configuration parameters and environment variables:

  • --p2p-bind-ip 127.0.0.1 on the command line or p2p-bind-ip=127.0.0.1 in 42d.conf to disable listening for connections on external interfaces.
  • --no-igd on the command line or no-igd=1 in 42d.conf to disable IGD (UPnP port forwarding negotiation), which is pointless with Tor.
  • DNS_PUBLIC=tcp or DNS_PUBLIC=tcp://x.x.x.x where x.x.x.x is the IP of the desired DNS server, for DNS requests to go over TCP, so that they are routed through Tor. When IP is not specified, 42d uses the default list of servers defined in src/common/dns_utils.cpp.
  • TORSOCKS_ALLOW_INBOUND=1 to tell torsocks to allow 42d to bind to interfaces to accept connections from the wallet. On some Linux systems, torsocks allows binding to localhost by default, so setting this variable is only necessary to allow binding to local LAN/VPN interfaces to allow wallets to connect from remote hosts. On other systems, it may be needed for local wallets as well.
  • Do NOT pass --detach when running through torsocks with systemd, (see utils/systemd/42od.service for details).
  • If you use the wallet with a Tor daemon via the loopback IP (eg, 127.0.0.1:9050), then use --untrusted-daemon unless it is your own hidden service.

Example command line to start 42d through Tor:

DNS_PUBLIC=tcp torsocks 42d --p2p-bind-ip 127.0.0.1 --no-igd

Using Tor on Tails

TAILS ships with a very restrictive set of firewall rules. Therefore, you need to add a rule to allow this connection too, in addition to telling torsocks to allow inbound connections. Full example:

sudo iptables -I OUTPUT 2 -p tcp -d 127.0.0.1 -m tcp --dport 18081 -j ACCEPT
DNS_PUBLIC=tcp torsocks ./42d --p2p-bind-ip 127.0.0.1 --no-igd --rpc-bind-ip 127.0.0.1 \
    --data-dir /home/amnesia/Persistent/your/directory/to/the/blockchain

Debugging

This section contains general instructions for debugging failed installs or problems encountered with 42. First ensure you are running the latest version built from the Github repo.

Obtaining stack traces and core dumps on Unix systems

We generally use the tool gdb (GNU debugger) to provide stack trace functionality, and ulimit to provide core dumps in builds which crash or segfault.

  • To use gdb in order to obtain a stack trace for a build that has stalled:

Run the build.

Once it stalls, enter the following command:

gdb /path/to/42d `pidof 42d` 

Type thread apply all bt within gdb in order to obtain the stack trace

  • If however the core dumps or segfaults:

Enter ulimit -c unlimited on the command line to enable unlimited filesizes for core dumps

Enter echo core | sudo tee /proc/sys/kernel/core_pattern to stop cores from being hijacked by other tools

Run the build.

When it terminates with an output along the lines of "Segmentation fault (core dumped)", there should be a core dump file in the same directory as 42d. It may be named just core, or core.xxxx with numbers appended.

You can now analyse this core dump with gdb as follows:

gdb /path/to/42d /path/to/dumpfile

Print the stack trace with bt

  • To run 42 within gdb:

Type gdb /path/to/42d

Pass command-line options with --args followed by the relevant arguments

Type run to run 42d

Analysing memory corruption

There are two tools available:

  • ASAN

Configure 42 with the -D SANITIZE=ON cmake flag, eg:

cd build/debug && cmake -D SANITIZE=ON -D CMAKE_BUILD_TYPE=Debug ../..

You can then run the 42 tools normally. Performance will typically halve.

  • valgrind

Install valgrind and run as valgrind /path/to/42d. It will be very slow.

LMDB

Instructions for debugging suspected blockchain corruption as per @HYC

There is an mdb_stat command in the LMDB source that can print statistics about the database but it's not routinely built. This can be built with the following command:

cd ~/42/external/db_drivers/liblmdb && make

The output of mdb_stat -ea <path to blockchain dir> will indicate inconsistencies in the blocks, block_heights and block_info table.

The output of mdb_dump -s blocks <path to blockchain dir> and mdb_dump -s block_info <path to blockchain dir> is useful for indicating whether blocks and block_info contain the same keys.

These records are dumped as hex data, where the first line is the key and the second line is the data.