### Usage

To build dependencies for the current arch+OS:

    make

To build for another arch/OS:

    make HOST=host-platform-triplet

For example:

    make HOST=x86_64-w64-mingw32 -j4

**Bitcoin Core's `configure` script by default will ignore the depends output.** In
order for it to pick up libraries, tools, and settings from the depends build,
you must set the `CONFIG_SITE` environment variable to point to a `config.site` settings file.
In the above example, a file named `depends/x86_64-w64-mingw32/share/config.site` will be
created. To use it during compilation:

    CONFIG_SITE=$PWD/depends/x86_64-w64-mingw32/share/config.site ./configure

The default install prefix when using `config.site` is `--prefix=depends/<host-platform-triplet>`,
so depends build outputs will be installed in that location.

Common `host-platform-triplet`s for cross compilation are:

- `i686-pc-linux-gnu` for Linux 32 bit
- `x86_64-pc-linux-gnu` for x86 Linux
- `x86_64-w64-mingw32` for Win64
- `x86_64-apple-darwin` for macOS
- `arm-linux-gnueabihf` for Linux ARM 32 bit
- `aarch64-linux-gnu` for Linux ARM 64 bit
- `powerpc64-linux-gnu` for Linux POWER 64-bit (big endian)
- `powerpc64le-linux-gnu` for Linux POWER 64-bit (little endian)
- `riscv32-linux-gnu` for Linux RISC-V 32 bit
- `riscv64-linux-gnu` for Linux RISC-V 64 bit
- `s390x-linux-gnu` for Linux S390X
- `armv7a-linux-android` for Android ARM 32 bit
- `aarch64-linux-android` for Android ARM 64 bit
- `i686-linux-android` for Android x86 32 bit
- `x86_64-linux-android` for Android x86 64 bit

The paths are automatically configured and no other options are needed unless targeting [Android](../doc/build-android.md).

### Install the required dependencies: Ubuntu & Debian

#### For macOS cross compilation

    sudo apt-get install curl librsvg2-bin libtiff-tools bsdmainutils cmake imagemagick libz-dev python3-setuptools libtinfo5 xorriso

Note: You must obtain the macOS SDK before proceeding with a cross-compile.
Under the depends directory, create a subdirectory named `SDKs`.
Then, place the extracted SDK under this new directory.
For more information, see [SDK Extraction](../contrib/macdeploy/README.md#sdk-extraction).

#### For Win64 cross compilation

- see [build-windows.md](../doc/build-windows.md#cross-compilation-for-ubuntu-and-windows-subsystem-for-linux)

#### For linux (including i386, ARM) cross compilation

Common linux dependencies:

    sudo apt-get install make automake cmake curl g++-multilib libtool binutils-gold bsdmainutils pkg-config python3 patch bison

For linux ARM cross compilation:

    sudo apt-get install g++-arm-linux-gnueabihf binutils-arm-linux-gnueabihf

For linux AARCH64 cross compilation:

    sudo apt-get install g++-aarch64-linux-gnu binutils-aarch64-linux-gnu

For linux POWER 64-bit cross compilation (there are no packages for 32-bit):

    sudo apt-get install g++-powerpc64-linux-gnu binutils-powerpc64-linux-gnu g++-powerpc64le-linux-gnu binutils-powerpc64le-linux-gnu

For linux RISC-V 64-bit cross compilation (there are no packages for 32-bit):

    sudo apt-get install g++-riscv64-linux-gnu binutils-riscv64-linux-gnu

RISC-V known issue: gcc-7.3.0 and gcc-7.3.1 result in a broken `test_bitcoin` executable (see https://github.com/bitcoin/bitcoin/pull/13543),
this is apparently fixed in gcc-8.1.0.

For linux S390X cross compilation:

    sudo apt-get install g++-s390x-linux-gnu binutils-s390x-linux-gnu

### Dependency Options

The following can be set when running make: `make FOO=bar`

- `SOURCES_PATH`: Downloaded sources will be placed here
- `BASE_CACHE`: Built packages will be placed here
- `SDK_PATH`: Path where SDKs can be found (used by macOS)
- `FALLBACK_DOWNLOAD_PATH`: If a source file can't be fetched, try here before giving up
- `NO_QT`: Don't download/build/cache Qt and its dependencies
- `NO_QR`: Don't download/build/cache packages needed for enabling qrencode
- `NO_ZMQ`: Don't download/build/cache packages needed for enabling ZeroMQ
- `NO_WALLET`: Don't download/build/cache libs needed to enable the wallet
- `NO_BDB`: Don't download/build/cache BerkeleyDB
- `NO_SQLITE`: Don't download/build/cache SQLite
- `NO_UPNP`: Don't download/build/cache packages needed for enabling UPnP
- `NO_NATPMP`: Don't download/build/cache packages needed for enabling NAT-PMP</dd>
- `ALLOW_HOST_PACKAGES`: Packages that are missed in dependencies (due to `NO_*` option or
  build script logic) are searched for among the host system packages using
  `pkg-config`. It allows building with packages of other (newer) versions
- `MULTIPROCESS`: Build libmultiprocess (experimental, requires CMake)
- `DEBUG`: Disable some optimizations and enable more runtime checking
- `HOST_ID_SALT`: Optional salt to use when generating host package ids
- `BUILD_ID_SALT`: Optional salt to use when generating build package ids
- `FORCE_USE_SYSTEM_CLANG`: (EXPERTS ONLY) When cross-compiling for macOS, use Clang found in the
  system's `$PATH` rather than the default prebuilt release of Clang
  from llvm.org. Clang 8 or later is required.

If some packages are not built, for example `make NO_WALLET=1`, the appropriate
options will be passed to bitcoin's configure. In this case, `--disable-wallet`.

### Additional targets

    download: run 'make download' to fetch all sources without building them
    download-osx: run 'make download-osx' to fetch all sources needed for macOS builds
    download-win: run 'make download-win' to fetch all sources needed for win builds
    download-linux: run 'make download-linux' to fetch all sources needed for linux builds


### Other documentation

- [description.md](description.md): General description of the depends system
- [packages.md](packages.md): Steps for adding packages