Merge commit '6791b57fa45112397746888cd5d2d326d6f1af89'

* commit '6791b57fa45112397746888cd5d2d326d6f1af89':
  Update CONTRIBUTING.md
  Add CONTRIBUTING.md

CONTRIBUTING.md

@@ -0,0 +1,251 @@
+# Contributing
+
+## Getting started
+
+## How to add a new image ? (With crosstool-ng)
+
+In this part, we will see how to add a new image, we will take example with `linux-arm64` for a raspberry pi 4, with [crosstool-ng](https://github.com/crosstool-ng/crosstool-ng).
+
+### Build and config crosstool-ng
+
+To start, you need to download the source code of crosstool-ng:
+
+```bash
+git clone --recurse-submodules --remote-submodules https://github.com/crosstool-ng/crosstool-ng.git
+```
+
+Go to crosstool-ng folder:
+
+```bash
+cd crosstool-ng
+```
+
+Change git branch:
+
+```bash
+git checkout crosstool-ng-1.25.0
+```
+
+Once in the **crosstool-ng** folder, you must first run the **bootstrap** script:
+
+```bash
+./bootstrap
+```
+
+Then run the **configure** script:
+
+*Note: ***--enable-local*** Do a portable install of crosstool-ng.*:
+
+```bash
+./configure --enable-local
+```
+
+Finally, launch the building of crosstool-ng:
+
+```bash
+make -j$(nproc)
+```
+
+Once the crosstool-ng build is complete, you can run this command to test crosstool-ng:
+
+```bash
+./ct-ng --version
+```
+
+Before starting the configuration of the toolchains, i recommend you to use one of the examples from crosstool-ng and then make your changes, the command to display the examples:
+
+```bash
+./ct-ng list-samples
+```
+
+We will take the example of **aarch64-rpi4-linux-gnu**, a **.config** file will be created:
+
+```bash
+./ct-ng aarch64-rpi4-linux-gnu
+```
+
+We will configure the toolchains according to our needs:
+
+```bash
+./ct-ng menuconfig
+```
+
+Once the modifications are made, we will display the name of the toolchains, it will be useful later:
+
+```bash
+./ct-ng show-tuple
+```
+
+### Configuring docker image
+
+You must create a file with the **same** name of the docker image (**linux-arm64**).
+
+Copy the **.config** of crosstool-ng to this file (**linux-arm64**) and rename it to **crosstool-ng.config**.
+
+You need to create a file named **Toolchain.cmake** in **linux-arm64**.
+
+Copy text to **Toolchain.cmake** file:
+
+```cmake
+set(CMAKE_SYSTEM_NAME Linux)
+set(CMAKE_SYSTEM_VERSION 1)
+set(CMAKE_SYSTEM_PROCESSOR ARM64)
+
+set(cross_triple $ENV{CROSS_TRIPLE})
+set(cross_root $ENV{CROSS_ROOT})
+
+set(CMAKE_C_COMPILER $ENV{CC})
+set(CMAKE_CXX_COMPILER $ENV{CXX})
+set(CMAKE_Fortran_COMPILER $ENV{FC})
+
+set(CMAKE_CXX_FLAGS "-I ${cross_root}/include/")
+
+set(CMAKE_FIND_ROOT_PATH ${cross_root} ${cross_root}/${cross_triple})
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY BOTH)
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE BOTH)
+set(CMAKE_SYSROOT ${cross_root}/${cross_triple}/sysroot)
+
+set(CMAKE_CROSSCOMPILING_EMULATOR /usr/bin/qemu-arm64)
+```
+
+Then ou must change these lines according to the targeted architecture, here **ARM64**:
+
+```cmake
+set(CMAKE_SYSTEM_PROCESSOR ARM64)
+set(CMAKE_CROSSCOMPILING_EMULATOR /usr/bin/qemu-arm64)
+```
+
+Then you must create a file named **Dockerfile.in** in the image folder (**linux-arm64**).
+
+Copy text to **Dockerfile.in** file:
+
+```docker
+FROM dockcross/base:latest
+
+LABEL maintainer="Matt McCormick matt.mccormick@kitware.com"
+
+# This is for 64-bit ARM Linux machine
+
+# Crosstool-ng crosstool-ng-1.25.0 2022-05-13
+ENV CT_VERSION crosstool-ng-1.25.0
+
+#include "common.crosstool"
+
+# The cross-compiling emulator
+RUN apt-get update \
+&& apt-get install -y \
+  qemu-user \
+  qemu-user-static \
+&& apt-get clean --yes
+
+# The CROSS_TRIPLE is a configured alias of the "aarch64-unknown-linux-gnu" target.
+ENV CROSS_TRIPLE aarch64-unknown-linux-gnu
+
+ENV CROSS_ROOT ${XCC_PREFIX}/${CROSS_TRIPLE}
+ENV AS=${CROSS_ROOT}/bin/${CROSS_TRIPLE}-as \
+    AR=${CROSS_ROOT}/bin/${CROSS_TRIPLE}-ar \
+    CC=${CROSS_ROOT}/bin/${CROSS_TRIPLE}-gcc \
+    CPP=${CROSS_ROOT}/bin/${CROSS_TRIPLE}-cpp \
+    CXX=${CROSS_ROOT}/bin/${CROSS_TRIPLE}-g++ \
+    LD=${CROSS_ROOT}/bin/${CROSS_TRIPLE}-ld \
+    FC=${CROSS_ROOT}/bin/${CROSS_TRIPLE}-gfortran
+
+ENV QEMU_LD_PREFIX "${CROSS_ROOT}/${CROSS_TRIPLE}/sysroot"
+ENV QEMU_SET_ENV "LD_LIBRARY_PATH=${CROSS_ROOT}/lib:${QEMU_LD_PREFIX}"
+
+COPY Toolchain.cmake ${CROSS_ROOT}/
+ENV CMAKE_TOOLCHAIN_FILE ${CROSS_ROOT}/Toolchain.cmake
+
+ENV PKG_CONFIG_PATH /usr/lib/aarch64-linux-gnu/pkgconfig
+
+# Linux kernel cross compilation variables
+ENV PATH ${PATH}:${CROSS_ROOT}/bin
+ENV CROSS_COMPILE ${CROSS_TRIPLE}-
+ENV ARCH arm64
+
+#include "common.label-and-env"
+```
+
+Then ou must change these lines according to the targeted architecture.
+
+Here you have to change the value according to the name of the toolchain (./ct-ng show-tuple):
+
+```docker
+ENV CROSS_TRIPLE aarch64-unknown-linux-gnu
+```
+
+These lines also need to be changed:
+
+```docker
+LABEL maintainer="Matt McCormick matt.mccormick@kitware.com"
+ENV PKG_CONFIG_PATH /usr/lib/aarch64-linux-gnu/pkgconfig
+ENV ARCH arm64
+```
+
+Once this part is finished, there must be 3 files in the **linux-arm64** folder:
+
+- **crosstool-ng.config**, the configuration of the toolchain/crosstool-ng.
+- **Dockerfile.in**, the docker file.
+- **Toolchain.cmake**, the CMake file for the toolchains.
+
+### Makefile and CI
+
+For this last part, we will see how to add the image to the [Makefile](Makefile) and to a github action.
+
+You need to add the image/folder name (**linux-arm64**) to the **STANDARD_IMAGES** variable in the [Makefile](Makefile):
+
+```make
+# These images are built using the "build implicit rule"
+STANDARD_IMAGES = android-arm android-arm64 android-x86 android-x86_64 \
+	linux-x86 linux-x64 linux-x64-clang linux-arm64 linux-arm64-musl linux-arm64-full \
+	linux-armv5 linux-armv5-musl linux-armv5-uclibc linux-m68k-uclibc linux-s390x linux-x64-tinycc \
+	linux-armv6 linux-armv6-lts linux-armv6-musl linux-arm64-lts \
+	linux-armv7l-musl linux-armv7 linux-armv7a linux-armv7-lts linux-x86_64-full \
+	linux-mips linux-ppc64le linux-riscv64 linux-riscv32 linux-xtensa-uclibc \
+	web-wasi \
+	windows-static-x86 windows-static-x64 windows-static-x64-posix windows-armv7 \
+	windows-shared-x86 windows-shared-x64 windows-shared-x64-posix windows-arm64
+```
+
+You need to add the image/folder name (**linux-arm64**) to the **GEN_IMAGES** variable in the [Makefile](Makefile):
+
+```make
+# Generated Dockerfiles.
+GEN_IMAGES = android-arm android-arm64 \
+	linux-x86 linux-x64 linux-x64-clang linux-arm64 linux-arm64-musl linux-arm64-full \
+	manylinux2014-x64 manylinux2014-x86 \
+	manylinux2014-aarch64 linux-arm64-lts \
+	web-wasm web-wasi linux-mips windows-arm64 windows-armv7 \
+	windows-static-x86 windows-static-x64 windows-static-x64-posix \
+	windows-shared-x86 windows-shared-x64 windows-shared-x64-posix \
+	linux-armv7 linux-armv7a linux-armv7l-musl linux-armv7-lts linux-x86_64-full \
+	linux-armv6 linux-armv6-lts linux-armv6-musl \
+	linux-armv5 linux-armv5-musl linux-armv5-uclibc linux-ppc64le linux-s390x \
+	linux-riscv64 linux-riscv32 linux-m68k-uclibc linux-x64-tinycc linux-xtensa-uclibc
+```
+
+To finish, you have to add to [Github Action](.github/workflows/main.yml) the image/folder name:
+
+```yml
+          # Linux arm64/armv8 images
+          - {
+              image: "linux-arm64",
+              stockfish: "yes",
+              stockfish_arg: "ARCH=armv8",
+              ninja: "yes",
+              ninja_arg: "",
+              openssl: "yes",
+              openssl_arg: "linux-aarch64",
+              C: "yes",
+              C_arg: "",
+              C-Plus-Plus: "yes",
+              C-Plus-Plus_arg: "",
+              fmt: "yes",
+              fmt_arg: "",
+              cpython: "yes",
+              cpython_arg: "--host=aarch64-unknown-linux-gnu --target=aarch64-unknown-linux-gnu",
+            }
+```
+
+You can disable and enable the build of certain tests which can cause problems with certain CPU architectures (eg. OpenSSL with Risc-V...).

README.md

@@ -31,10 +31,15 @@ Cross compiling toolchains in Docker images.
 5. `dockcross bash`: Run an interactive shell in the build environment.
 
 Note that commands are executed verbatim. If any shell processing for environment variable expansion or redirection is required, please use
+
 ```bash
 bash -c "<command args>"
 ```
 
+## Contributing
+
+See [CONTRIBUTING.md](CONTRIBUTING.md).
+
 ## Installation
 
 This image does not need to be run manually. Instead, there is a helper script to execute build commands on source code existing on the local host filesystem. This script is bundled with the image.
@@ -546,5 +551,6 @@ The key difference is that [dockbuild](https://github.com/dockbuild/dockbuild#re
 \-\--
 
 Credits:
+
 - [sdt/docker-raspberry-pi-cross-compiler](https://github.com/sdt/docker-raspberry-pi-cross-compiler), who invented the base of the **dockcross** script.
 - [https://github.com/steeve/cross-compiler](https://github.com/steeve/cross-compiler),