### 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

A prefix will be generated that's suitable for plugging into Bitcoin's
configure. In the above example, a dir named x86_64-w64-mingw32 will be
created. To use it for Bitcoin:

    ./configure --prefix=`pwd`/depends/x86_64-w64-mingw32

Common `host-platform-triplets` for cross compilation are:

- `i686-w64-mingw32` for Win32
- `x86_64-w64-mingw32` for Win64
- `x86_64-apple-darwin14` for macOS
- `arm-linux-gnueabihf` for Linux ARM 32 bit
- `aarch64-linux-gnu` for Linux ARM 64 bit
- `riscv32-linux-gnu` for Linux RISC-V 32 bit
- `riscv64-linux-gnu` for Linux RISC-V 64 bit

No other options are needed, the paths are automatically configured.

### Install the required dependencies: Ubuntu & Debian

First, install the common dependencies:

    sudo apt-get install autoconf automake cmake bsdmainutils ca-certificates curl faketime g++ libtool pkg-config

#### For macOS cross compilation:

    sudo apt-get install librsvg2-bin libtiff-tools imagemagick libcap-dev libz-dev libbz2-dev python-setuptools

#### For Win32/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 g++-multilib binutils-gold bsdmainutils

For linux ARM cross compilation:

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

For linux AARCH64 cross compilation:

    sudo apt-get install g++-arm-linux-gnueabihf binutils-arm-linux-gnueabihf
    
For linux RISC-V 64-bit cross compilation (there are no packages for 32-bit):

    sudo apt-get install curl 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.

### 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 sdk's 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_WALLET: Don't download/build/cache libs needed to enable the wallet
    NO_UPNP: Don't download/build/cache packages needed for enabling upnp
    DEBUG: disable some optimizations and enable more runtime checking
    RAPIDCHECK: build rapidcheck (experimental)
    HOST_ID_SALT: Optional salt to use when generating host package ids
    BUILD_ID_SALT: Optional salt to use when generating build package ids

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