apache · kou · Apr 5, 2024 · Sep 21, 2023 · Sep 21, 2023 · Sep 25, 2023
diff --git a/cpp/CMakePresets.json b/cpp/CMakePresets.json
@@ -46,6 +46,32 @@
         "CMAKE_BUILD_TYPE": "RelWithDebInfo"
       }
     },
+    {
+      "name": "emscripten-overrides",
+      "hidden": true,
+      "cacheVariables": {
+        "ARROW_BUILD_SHARED": "OFF",
+        "ARROW_BUILD_STATIC": "ON",
+        "ARROW_BUILD_TESTS": "OFF",
+        "ARROW_ENABLE_THREADING": "OFF",
+        "ARROW_CUDA": "OFF",
+        "ARROW_MIMALLOC": "OFF",
+        "ARROW_JEMALLOC": "OFF",
+        "ARROW_S3": "OFF",
+        "ARROW_DEPENDENCY_SOURCE": "BUNDLED",
+        "ZLIB_SOURCE": "SYSTEM",
+        "ARROW_IPC": "OFF",
+        "ARROW_ORC": "OFF",
+        "ARROW_SUBSTRAIT": "OFF",
+        "ARROW_DEPENDENCY_USE_SHARED": "OFF",
+        "ARROW_WITH_BROTLI": "OFF",
+        "ARROW_SIMD_LEVEL":"NONE",
+        "ARROW_RUNTIME_SIMD_LEVEL":"NONE",
+        "CMAKE_C_BYTE_ORDER":"LITTLE_ENDIAN",
+        "ARROW_WITH_OPENTELEMETRY":"OFF",
+        "CMAKE_TOOLCHAIN_FILE": { "type": "PATH", "value": "${sourceDir}/cmake_modules/Emscripten/Platform/EmscriptenOverrides.cmake" }
+      }
+    },
     {
       "name": "features-minimal",
       "hidden": true,
@@ -395,6 +421,16 @@
       "displayName": "Release build for PyArrow with everything enabled",
       "cacheVariables": {}
     },
+    {
+      "name": "ninja-release-emscripten-python",
+      "inherits": [
+        "emscripten-overrides",
+        "base-release",
+        "features-python"
+      ],
+      "displayName": "Release build which builds an emscripten library, plus PyArrow for Pyodide",
+      "cacheVariables": {}
+    },
     {
       "name": "ninja-release-maximal",
       "inherits": [

diff --git a/cpp/cmake_modules/Emscripten/Platform/EmscriptenOverrides.cmake b/cpp/cmake_modules/Emscripten/Platform/EmscriptenOverrides.cmake
@@ -0,0 +1,56 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+# Force some variables for emscripten
+# to disable things that won't work there
+
+# make us be on the platforms list for cmake
+get_filename_component(PLATFORM_FOLDER_PARENT ${CMAKE_CURRENT_LIST_DIR} DIRECTORY)
+list(APPEND CMAKE_MODULE_PATH "${PLATFORM_FOLDER_PARENT}")
+
+include($ENV{EMSDK}/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake)
+
+# ensure zlib is built with -fpic
+# and force us to link to the version in emscripten ports
+if(NOT EXISTS ${EMSCRIPTEN_SYSROOT}/lib/wasm32-emscripten/pic/libz.a)
+  execute_process(COMMAND embuilder --pic --force build zlib)
+endif()
+set(ZLIB_LIBRARY ${EMSCRIPTEN_SYSROOT}/lib/wasm32-emscripten/pic/libz.a)
+
+# # override default in emscripten which is to not use shared libs
+set_property(GLOBAL PROPERTY TARGET_SUPPORTS_SHARED_LIBS TRUE)
+
+# if we leave the system name as Emscripten, then it reloads the original Emscripten.cmake every time a project() command
+# is run, which does bad things like disabling shared libraries
+set(CMAKE_SYSTEM_NAME EmscriptenOverrides)
+
+set(CMAKE_C_FLAGS "-sUSE_ZLIB=1 -sSIDE_MODULE=1 -fPIC -fexceptions")
+set(CMAKE_CXX_FLAGS "-sUSE_ZLIB=1 -sSIDE_MODULE=1 -fPIC -fexceptions")
+
+#set(PYARROW_CPP_HOME "$ENV{ARROW_HOME}/lib")
+#list(APPEND CMAKE_FIND_ROOT_PATH "${CMAKE_INSTALL_PREFIX}/cmake")
+
+set(Python3_INCLUDE_DIR $ENV{PYTHONINCLUDE})
+set(Python3_LIBRARY $ENV{CPYTHONLIB})
+set(Python3_NumPy_INCLUDE_DIR $ENV{NUMPY_LIB}/core/include)
+set(Python3_EXECUTABLE)
+set(CMAKE_SHARED_LIBRARY_CREATE_C_FLAGS "-sUSE_ZLIB=1 -sWASM_BIGINT=1 -fexceptions")
+set(CMAKE_SHARED_LIBRARY_CREATE_CXX_FLAGS "-sUSE_ZLIB=1 -sWASM_BIGINT=1 -fexceptions")
+set(CMAKE_SHARED_LINKER_FLAGS "-sUSE_ZLIB=1 -sWASM_BIGINT=1 -fexceptions")
+set(CMAKE_STRIP FALSE)
+
+set(ENV{_PYTHON_SYSCONFIGDATA_NAME} $ENV{SYSCONFIG_NAME})
diff --git a/cpp/cmake_modules/SetupCxxFlags.cmake b/cpp/cmake_modules/SetupCxxFlags.cmake
@@ -24,7 +24,9 @@ include(CheckCXXSourceCompiles)
 message(STATUS "System processor: ${CMAKE_SYSTEM_PROCESSOR}")
 
 if(NOT DEFINED ARROW_CPU_FLAG)
-  if(CMAKE_SYSTEM_PROCESSOR MATCHES "AMD64|amd64|X86|x86|i[3456]86|x64")
+  if(CMAKE_SYSTEM_NAME MATCHES "Emscripten")
+    set(ARROW_CPU_FLAG "emscripten")
+  elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "AMD64|amd64|X86|x86|i[3456]86|x64")
     set(ARROW_CPU_FLAG "x86")
   elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64|ARM64|arm64")
     set(ARROW_CPU_FLAG "aarch64")

diff --git a/cpp/cmake_modules/ThirdpartyToolchain.cmake b/cpp/cmake_modules/ThirdpartyToolchain.cmake
@@ -955,6 +955,11 @@ set(EP_COMMON_CMAKE_ARGS
     -DCMAKE_OSX_SYSROOT=${CMAKE_OSX_SYSROOT}
     -DCMAKE_VERBOSE_MAKEFILE=${CMAKE_VERBOSE_MAKEFILE})
 
+# if building with a toolchain file, pass that through
+if(CMAKE_TOOLCHAIN_FILE)
+  list(APPEND EP_COMMON_CMAKE_ARGS -DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE})
+endif()
+
 # Enable s/ccache if set by parent.
 if(CMAKE_C_COMPILER_LAUNCHER AND CMAKE_CXX_COMPILER_LAUNCHER)
   list(APPEND EP_COMMON_CMAKE_ARGS
@@ -1614,6 +1619,9 @@ macro(build_thrift)
   if(DEFINED BOOST_ROOT)
     list(APPEND THRIFT_CMAKE_ARGS "-DBOOST_ROOT=${BOOST_ROOT}")
   endif()
+  if(DEFINED Boost_INCLUDE_DIR)
+    list(APPEND THRIFT_CMAKE_ARGS "-DBoost_INCLUDE_DIR=${Boost_INCLUDE_DIR}")
+  endif()
   if(DEFINED Boost_NAMESPACE)
     list(APPEND THRIFT_CMAKE_ARGS "-DBoost_NAMESPACE=${Boost_NAMESPACE}")
   endif()

diff --git a/docs/source/developers/cpp/emscripten.rst b/docs/source/developers/cpp/emscripten.rst
@@ -0,0 +1,100 @@
+.. Licensed to the Apache Software Foundation (ASF) under one
+.. or more contributor license agreements.  See the NOTICE file
+.. distributed with this work for additional information
+.. regarding copyright ownership.  The ASF licenses this file
+.. to you under the Apache License, Version 2.0 (the
+.. "License"); you may not use this file except in compliance
+.. with the License.  You may obtain a copy of the License at
+
+..   http://www.apache.org/licenses/LICENSE-2.0
+
+.. Unless required by applicable law or agreed to in writing,
+.. software distributed under the License is distributed on an
+.. "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+.. KIND, either express or implied.  See the License for the
+.. specific language governing permissions and limitations
+.. under the License.
+
+
+.. highlight:: console .. _developers-cpp-emscripten:
+
+#################################################
+ Cross compiling for Webassembly with Emscripten
+#################################################
+
+***************
+ Prerequisites
+***************
+You need cmake and compilers etc. installed as per the normal build instructions. Before building with emscripten, you also need to install emscripten and
+activate it using the commands below (see https://emscripten.org/docs/getting_started/downloads.html for details).
+
+.. code:: shell
+
+   git clone https://github.com/emscripten-core/emsdk.git
+   cd emsdk
+   # replace <version> with the desired EMSDK version.
+   # e.g. for pyodide 0.24, you need EMSDK version 3.1.45
+   ./emsdk install <version>
+   ./emsdk activate <version>
+   source ./emsdk_env.sh
+
+If you want to build pyarrow for `pyodide <https://pyodide.org>`_, you
+need ``pyodide-build`` installed via ``pip``, and to be running with the
+same version of python that pyodide is built for, along with the same
+versions of emsdk.
+
+.. code:: shell
+
+   # install pyodide build tools.
+   # e.g. for version 0.24 of pyodide:
+   pip install pyodide-build==0.24
+
+Then build with the ``ninja-release-emscripten-python`` cmake preset,
+like below:
+
+.. code:: shell
+
+   cmake --preset "ninja-release-emscripten-python"
+   ninja install
+
+This will install a built static library version of libarrow it into the
+emscripten sysroot cache, meaning you can build things that depend on it
+and they will find libarrow.
+
+e.g. if you want to build for pyodide, run the commands above, and then
+go to ``arrow/python`` and run
+
+.. code:: shell
+
+   pyodide build
+
+It should make a wheel targeting the currently enabled version of
+pyodide (i.e. the version corresponding to the currently installed
+``pyodide-build``) in the ``dist`` subdirectory.
+
+**************
+ Manual Build
+**************
+
+If you want to manually build for emscripten, take a look at the
+CMakePresets.json file in the arrow/cpp directory for a list of things
+you will need to override. In particular you will need:
+
+#. Build dependencies set to ``BUNDLED``, so it uses properly cross
+   compiled build dependencies.
+
+#. ``CMAKE_TOOLCHAIN_FILE`` set to
+   ``arrow/cpp/cmake_modules/Emscripten/Platform/EmscriptenOverrides.cmake``
+
+#. You will quite likely need to set ``ARROW_ENABLE_THREADING`` to ``OFF``
+   for builds targeting single threaded emscripten environments such as
+   pyodide.
+
+#. ``ARROW_IPC`` and anything else that uses network probably won't
+   work.
+
+#. ``ARROW_JEMALLOC`` and ``ARROW_MIMALLOC`` again probably need to be
+   ``OFF``
+
+#. ``ARROW_BUILD_STATIC`` set to ``ON`` and ``ARROW_BUILD_SHARED`` set to
+   ``OFF`` is most likely to work.
diff --git a/docs/source/developers/cpp/index.rst b/docs/source/developers/cpp/index.rst
@@ -27,5 +27,6 @@ C++ Development
    building
    development
    windows
+   emscripten
    conventions
    fuzzing