mgba WebAssembly support

Hey there. I'm curious if anyone has tried running mGBA under WebAssembly, since I might have a use case for such a thing (in the somewhat distant future). If so... how did it go?

If not, I'm keen for a bit of pioneering (though I'm pretty busy over the next couple of months, but should have time after that).

Is anyone able to forsee any potential issues off the bat?

Feb 07 '19 19:02 nelsonxb

This is actually on the roadmap for mGBA 0.8, but I haven't tried it yet.

Feb 07 '19 20:02 endrift

Sweet! I'll follow up if I get the time to look into it. I'm comfortable with C myself, so if I get to it first then I'm happy to submit patches if need be.

Feb 08 '19 04:02 nelsonxb

Also, would be stoked on this! 😀 Let me know if you need help on the JS side of things!

Feb 16 '19 12:02 torch2424

Just a tip if someone arrive here by google...

I'm wrapping the emulator on web app gbajs into a React component, so you'll can embed it on your project. I'm doing it because I need a GBA emulator that runs on browser, and gbajs was the unique option that I found.

I think that on the next weeks I'll launch this package, react-gbajs.

Edit: package published 🎉

www.github.com/macabeus/react-gbajs

Nov 18 '19 05:11 macabeus

I have this mostly done but I'm still missing a decent frontend.

Jan 28 '21 04:01 endrift

@endrift Is there a branch or a commit I could test out :) I don't need much of a front end. Just want to mess around. What's the performance like?

Mar 18 '21 16:03 patrickcorrigan

Branch is here: https://github.com/endrift/mgba/tree/feature/wasm but it's been a while since I toyed with it so I don't remember.

Mar 18 '21 20:03 endrift

Sweet. I just cloned it. How do I build it? I tried cmake -DCMAKE_TOOLCHAIN_FILE=../src/platform/wasm .. and got

CMake Error at src/platform/wasm/CMakeLists.txt:11 (set_target_properties):
  set_target_properties called with incorrect number of arguments.
Call Stack (most recent call first):
  CMakeFiles/3.15.2/CMakeSystem.cmake:6 (include)
  CMakeLists.txt:10 (project)


-- The C compiler identification is AppleClang 12.0.0.12000032
-- The CXX compiler identification is AppleClang 12.0.0.12000032
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain
/usr/bin/cc
CMake Error at /Users/patrickcorrigan/Documents/GitHub/mgba/src/platform/wasm/CMakeLists.txt:11 (set_target_pro
perties):
  set_target_properties called with incorrect number of arguments.
Call Stack (most recent call first):
  /Users/patrickcorrigan/Documents/GitHub/mgba/CMakeFiles/3.15.2/CMakeSystem.cmake:6 (include)
  /Users/patrickcorrigan/Documents/GitHub/mgba/CMakeFiles/CMakeTmp/CMakeLists.txt:3 (project)


CMake Error at /opt/local/share/cmake-3.15/Modules/CMakeTestCCompiler.cmake:44 (try_compile):
  Failed to configure test project build system.
Call Stack (most recent call first):
  CMakeLists.txt:10 (project)


-- Configuring incomplete, errors occurred!
See also "/Users/patrickcorrigan/Documents/GitHub/mgba/CMakeFiles/CMakeOutput.log".
See also "/Users/patrickcorrigan/Documents/GitHub/mgba/CMakeFiles/CMakeError.log".```

Mar 18 '21 22:03 patrickcorrigan

You'll need emscripten, but beyond that I don't know. I use a Docker image to build it (which is publicly available--https://hub.docker.com/r/mgba/wasm), but if you're on macOS Docker is a pain.

Mar 18 '21 23:03 endrift

Awesome. I installed virtual box and have a ubuntu image running. I can get the docker container to the point where it complains about emscripten

I get this error.

shared:ERROR: '/emsdk_portable/clang/tag-e1.39.4/build_tag-e1.39.4_64/bin/clang -target asmjs-unknown-emscripten -D__EMSCRIPTEN_major__=1 -D__EMSCRIPTEN_minor__=39 -D__EMSCRIPTEN_tiny__=4 -D_LIBCPP_ABI_VERSION=2 -Werror=implicit-function-declaration -Xclang -nostdsysteminc -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/include/libcxx -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/lib/libcxxabi/include -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/include/compat -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/include -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/include/libc -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/lib/libc/musl/arch/emscripten -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/local/include -DBUILD_GL -DENABLE_SCRIPTING -DHAVE_CHMOD -DHAVE_CRC32 -DHAVE_LOCALE -DHAVE_LOCALTIME_R -DHAVE_SETLOCALE -DHAVE_STRDUP -DHAVE_STRNDUP -DHAVE_STRTOF_L -DHAVE_UMASK -DM_CORE_GB -DM_CORE_GBA -DUSE_DEBUGGERS -DUSE_GDB_STUB -DUSE_LZMA -DUSE_PNG -DUSE_PTHREADS -DUSE_SQLITE3 -DUSE_ZLIB -D_7ZIP_PPMD_SUPPPORT -I/home/mgba/src/src -I/home/mgba/src/include -I/home/mgba/src/src/third-party/zlib -I/home/mgba/src/build-wasm/zlib -I/home/mgba/src/src/third-party/libpng -I/home/mgba/src/build-wasm/libpng -I/home/mgba/src/src/third-party/sqlite3 -I/home/mgba/src/src/third-party/lzma -Wall -Wextra -Wno-missing-field-initializers -std=c99 -pthread -DNDEBUG -O2 -c -DEMSCRIPTEN -D__EMSCRIPTEN_PTHREADS__=1 -mllvm -disable-llvm-optzns /home/mgba/src/src/core/cheats.c -Xclang -disable-O0-optnone -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/include/SDL -c -o CMakeFiles/mgba.dir/src/core/cheats.c.o -emit-llvm' failed (1)
CMakeFiles/mgba.dir/build.make:88: recipe for target 'CMakeFiles/mgba.dir/src/core/cheats.c.o' failed

Can you remember how you installed emscripten? I tried installing it globally on the host ubuntu machine. Looks like I need to put it in /emsdk_portable/???

Update - Nevermind I cloned the repo but forgot to check out the correct branch :)

Mar 19 '21 15:03 patrickcorrigan

So I have the docker image running to this point now

error: invalid argument '-std=c++03' not allowed with 'C'
-- Symbol prefix:
-- Could NOT find PkgConfig (missing:  PKG_CONFIG_EXECUTABLE)
-- Checking for one of the modules 'sdl2'
-- Could NOT find SDL2 (missing:  SDL2_LIBRARIES SDL2_INCLUDE_DIRS)
-- Could NOT find SDL (missing:  SDL_LIBRARY) (found suitable version "1.3.0", minimum required is "1.2")
-- Build type: Release
-- Platforms:
--      Game Boy Advance: ON
--      Game Boy: ON
-- Features:
--      Debuggers: ON
--      Screenshot/advanced savestate support: ON
--      ZIP support: minizip (included)
--      7-Zip support: ON
--      ELF loading support: OFF
--      OpenGL support: OpenGL, OpenGL|ES 2
-- Frontends:
--      Qt:
--      SDL (2): ON
--      Profiling: OFF
--      Test harness: OFF
--      Test suite: OFF
--      Video test suite: OFF
--      Python bindings: OFF
--      Examples: OFF
-- Cores:
--      Libretro core: OFF
-- Libraries:
--      Static: ON
--      Shared: OFF
CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
OPENGLES2_LIBRARY
    linked by target "mgba" in directory /home/mgba/src
 
-- Configuring incomplete, errors occurred!
See also "/home/mgba/src/build-wasm/CMakeFiles/CMakeOutput.log".
See also "/home/mgba/src/build-wasm/CMakeFiles/CMakeError.log".

Any ideas? Sorry I'm mostly a web developer

Mar 19 '21 16:03 patrickcorrigan

So I have the docker image running to this point now
error: invalid argument '-std=c++03' not allowed with 'C'

Looks like it's trying to build mgba with a C++ standard. Try -std=c11 instead. I don't know whether that's what the code was written to conform with, but it's a start.

-- Symbol prefix: -- Could NOT find PkgConfig (missing: PKG_CONFIG_EXECUTABLE)

This should do the trick: sudo apt update && sudo apt install pkg-config

-- Checking for one of the modules 'sdl2' -- Could NOT find SDL2 (missing: SDL2_LIBRARIES SDL2_INCLUDE_DIRS) -- Could NOT find SDL (missing: SDL_LIBRARY) (found suitable version "1.3.0", minimum required is "1.2")

This should work for this one: sudo apt update && sudo apt install libsdl2 libsdl2-dev libsdl1.2-dev

-- Build type: Release -- Platforms: -- Game Boy Advance: ON -- Game Boy: ON -- Features: -- Debuggers: ON -- Screenshot/advanced savestate support: ON -- ZIP support: minizip (included) -- 7-Zip support: ON -- ELF loading support: OFF -- OpenGL support: OpenGL, OpenGL|ES 2 -- Frontends: -- Qt: -- SDL (2): ON -- Profiling: OFF -- Test harness: OFF -- Test suite: OFF -- Video test suite: OFF -- Python bindings: OFF -- Examples: OFF -- Cores: -- Libretro core: OFF -- Libraries: -- Static: ON -- Shared: OFF CMake Error: The following variables are used in this project, but they are set to NOTFOUND. Please set them or make sure they are set and tested correctly in the CMake files: OPENGLES2_LIBRARY linked by target "mgba" in directory /home/mgba/src

-- Configuring incomplete, errors occurred! See also "/home/mgba/src/build-wasm/CMakeFiles/CMakeOutput.log". See also "/home/mgba/src/build-wasm/CMakeFiles/CMakeError.log".
Any ideas? Sorry I'm mostly a web developer

Hopefully this helps

Mar 21 '21 18:03 brainard52

Looks like it's trying to build mgba with a C++ standard. Try -std=c11 instead. I don't know whether that's what the code was written to conform with, but it's a start.

Whatever is telling it to use a C++ standard isn't coming from mGBA's code, so tracking down where that's coming from would be the real issue here.

-- Symbol prefix: -- Could NOT find PkgConfig (missing: PKG_CONFIG_EXECUTABLE)

This should do the trick: sudo apt update && sudo apt install pkg-config

This isn't needed. It's not an error and none of the things found with pkg-config would be used here anyway.

-- Checking for one of the modules 'sdl2' -- Could NOT find SDL2 (missing: SDL2_LIBRARIES SDL2_INCLUDE_DIRS) -- Could NOT find SDL (missing: SDL_LIBRARY) (found suitable version "1.3.0", minimum required is "1.2")

This should work for this one: sudo apt update && sudo apt install libsdl2 libsdl2-dev libsdl1.2-dev

This is the webassembly build, a native version of SDL isn't going to help here.

Mar 21 '21 19:03 endrift

I've pushed a fix for the GLESv2 issue, it actually builds now despite the warnings.

Mar 21 '21 19:03 endrift

That's awesome! Are you building using the docker image?

Mar 21 '21 20:03 patrickcorrigan

Yup.

Mar 21 '21 20:03 endrift

Building using you latest push and the docker image I now get this.

docker run --rm -t -v $PWD:/home/mgba/src  mgba/wasm
-- Checking for one of the modules 'libedit'
CMake Warning at CMakeLists.txt:144 (message):
  Requested module libedit missing for feature USE_EDITLINE.  Feature
  disabled.
Call Stack (most recent call first):
  CMakeLists.txt:407 (find_feature)


-- Checking for one of the modules 'libavcodec'
CMake Warning at CMakeLists.txt:144 (message):
  Requested module libavcodec missing for feature USE_FFMPEG.  Feature
  disabled.
Call Stack (most recent call first):
  CMakeLists.txt:434 (find_feature)


-- Checking for one of the modules 'ZLIB'
CMake Warning at CMakeLists.txt:144 (message):
  Requested module ZLIB missing for feature USE_ZLIB.  Feature disabled.
Call Stack (most recent call first):
  CMakeLists.txt:435 (find_feature)


-- Checking for one of the modules 'minizip'
CMake Warning at CMakeLists.txt:144 (message):
  Requested module minizip missing for feature USE_MINIZIP.  Feature
  disabled.
Call Stack (most recent call first):
  CMakeLists.txt:436 (find_feature)


-- Checking for one of the modules 'PNG'
CMake Warning at CMakeLists.txt:144 (message):
  Requested module PNG missing for feature USE_PNG.  Feature disabled.
Call Stack (most recent call first):
  CMakeLists.txt:437 (find_feature)


-- Checking for one of the modules 'libzip'
CMake Warning at CMakeLists.txt:144 (message):
  Requested module libzip missing for feature USE_LIBZIP.  Feature disabled.
Call Stack (most recent call first):
  CMakeLists.txt:438 (find_feature)


-- Checking for one of the modules 'MagickWand'
CMake Warning at CMakeLists.txt:144 (message):
  Requested module MagickWand missing for feature USE_MAGICK.  Feature
  disabled.
Call Stack (most recent call first):
  CMakeLists.txt:439 (find_feature)


-- Checking for one of the modules 'epoxy'
CMake Warning at CMakeLists.txt:144 (message):
  Requested module epoxy missing for feature USE_EPOXY.  Feature disabled.
Call Stack (most recent call first):
  CMakeLists.txt:440 (find_feature)


-- Checking for one of the modules 'sqlite3'
CMake Warning at CMakeLists.txt:144 (message):
  Requested module sqlite3 missing for feature USE_SQLITE3.  Feature
  disabled.
Call Stack (most recent call first):
  CMakeLists.txt:442 (find_feature)


-- Checking for one of the modules 'libelf'
CMake Warning at CMakeLists.txt:144 (message):
  Requested module libelf missing for feature USE_ELF.  Feature disabled.
Call Stack (most recent call first):
  CMakeLists.txt:443 (find_feature)


CMake Warning (dev) at src/third-party/zlib/CMakeLists.txt:186 (add_library):
  ADD_LIBRARY called with SHARED option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Warning (dev) at CMakeLists.txt:799 (add_library):
  ADD_LIBRARY called with SHARED option but the target platform does not
  support dynamic linking.  Building a STATIC library instead.  This may lead
  to problems.
This warning is for project developers.  Use -Wno-dev to suppress it.

-- Checking for one of the modules 'sdl2'
-- Could NOT find SDL (missing:  SDL_LIBRARY) (found suitable version "1.3.0", minimum required is "1.2")
CMake Warning at src/platform/qt/CMakeLists.txt:25 (find_package):
  By not providing "FindQt5Multimedia.cmake" in CMAKE_MODULE_PATH this
  project has asked CMake to find a package configuration file provided by
  "Qt5Multimedia", but CMake did not find one.

  Could not find a package configuration file provided by "Qt5Multimedia"
  with any of the following names:

    Qt5MultimediaConfig.cmake
    qt5multimedia-config.cmake

  Add the installation prefix of "Qt5Multimedia" to CMAKE_PREFIX_PATH or set
  "Qt5Multimedia_DIR" to a directory containing one of the above files.  If
  "Qt5Multimedia" provides a separate development package or SDK, be sure it
  has been installed.


CMake Warning at src/platform/qt/CMakeLists.txt:26 (find_package):
  By not providing "FindQt5OpenGL.cmake" in CMAKE_MODULE_PATH this project
  has asked CMake to find a package configuration file provided by
  "Qt5OpenGL", but CMake did not find one.

  Could not find a package configuration file provided by "Qt5OpenGL" with
  any of the following names:

    Qt5OpenGLConfig.cmake
    qt5opengl-config.cmake

  Add the installation prefix of "Qt5OpenGL" to CMAKE_PREFIX_PATH or set
  "Qt5OpenGL_DIR" to a directory containing one of the above files.  If
  "Qt5OpenGL" provides a separate development package or SDK, be sure it has
  been installed.


CMake Warning at src/platform/qt/CMakeLists.txt:27 (find_package):
  By not providing "FindQt5Widgets.cmake" in CMAKE_MODULE_PATH this project
  has asked CMake to find a package configuration file provided by
  "Qt5Widgets", but CMake did not find one.

  Could not find a package configuration file provided by "Qt5Widgets" with
  any of the following names:

    Qt5WidgetsConfig.cmake
    qt5widgets-config.cmake

  Add the installation prefix of "Qt5Widgets" to CMAKE_PREFIX_PATH or set
  "Qt5Widgets_DIR" to a directory containing one of the above files.  If
  "Qt5Widgets" provides a separate development package or SDK, be sure it has
  been installed.


CMake Warning at src/platform/qt/CMakeLists.txt:35 (message):
  Cannot find Qt modules


-- Build type: Release
-- Platforms:
-- 	Game Boy Advance: ON
-- 	Game Boy: ON
-- Features:
-- 	Debuggers: ON
-- 	CLI debugger: OFF
-- 	GDB stub: ON
-- 	Video recording: OFF
-- 	GIF recording: OFF
-- 	Screenshot/advanced savestate support: ON
-- 	ZIP support: minizip (included)
-- 	7-Zip support: ON
-- 	SQLite3 game database: ON
-- 	ELF loading support: OFF
-- 	OpenGL support: OpenGL
-- Frontends:
-- 	Qt: ON
-- 	SDL (2): ON
-- 	Profiling: OFF
-- 	Test harness: OFF
-- 	Test suite: OFF
-- 	Python bindings: OFF
-- 	Examples: OFF
-- Cores:
-- 	Libretro core: OFF
-- Libraries:
-- 	Static: OFF
-- 	Shared: ON
-- Configuring done
CMake Warning (dev) at src/third-party/libpng/CMakeLists.txt:130 (add_library):
  Policy CMP0003 should be set before this line.  Add code such as

    if(COMMAND cmake_policy)
      cmake_policy(SET CMP0003 NEW)
    endif(COMMAND cmake_policy)

  as early as possible but after the most recent call to
  cmake_minimum_required or cmake_policy(VERSION).  This warning appears
  because target "png16_static" links to some libraries for which the linker
  must search:

    m

  and other libraries with known full path:

    /home/mgba/src/build-wasm/zlib/libz.a

  CMake is adding directories in the second list to the linker search path in
  case they are needed to find libraries from the first list (for backwards
  compatibility with CMake 2.4).  Set policy CMP0003 to OLD or NEW to enable
  or disable this behavior explicitly.  Run "cmake --help-policy CMP0003" for
  more information.
This warning is for project developers.  Use -Wno-dev to suppress it.

-- Generating done
-- Build files have been written to: /home/mgba/src/build-wasm
[  0%] Built target version-info
[  8%] Built target zlibstatic
[ 16%] Built target png16_static
[ 16%] Building C object CMakeFiles/mgba.dir/src/core/cheats.c.o
In file included from /home/mgba/src/src/core/cheats.c:8:
In file included from /home/mgba/src/include/mgba/core/core.h:15:
/home/mgba/src/include/mgba/core/directories.h:17:16: error: use of undeclared identifier 'PATH_MAX'
        char baseName[PATH_MAX];
                      ^
/home/mgba/src/src/core/cheats.c:77:15: error: implicit declaration of function 'strdup' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
                set->name = strdup(name);
                            ^
/home/mgba/src/src/core/cheats.c:77:13: warning: incompatible integer to pointer conversion assigning to 'char *' from 'int' [-Wint-conversion]
                set->name = strdup(name);
                          ^ ~~~~~~~~~~~~
/home/mgba/src/src/core/cheats.c:103:15: error: implicit declaration of function 'strdup' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
                set->name = strdup(name);
                            ^
/home/mgba/src/src/core/cheats.c:103:13: warning: incompatible integer to pointer conversion assigning to 'char *' from 'int' [-Wint-conversion]
                set->name = strdup(name);
                          ^ ~~~~~~~~~~~~
/home/mgba/src/src/core/cheats.c:111:35: error: implicit declaration of function 'strdup' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        *StringListAppend(&set->lines) = strdup(line);
                                         ^
/home/mgba/src/src/core/cheats.c:111:33: warning: incompatible integer to pointer conversion assigning to 'char *' from 'int' [-Wint-conversion]
        *StringListAppend(&set->lines) = strdup(line);
                                       ^ ~~~~~~~~~~~~
/home/mgba/src/src/core/cheats.c:189:37: error: implicit declaration of function 'strdup' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
                        *StringListAppend(&directives) = strdup(&cheat[i]);
                                                         ^
/home/mgba/src/src/core/cheats.c:189:35: warning: incompatible integer to pointer conversion assigning to 'char *' from 'int' [-Wint-conversion]
                        *StringListAppend(&directives) = strdup(&cheat[i]);
                                                       ^ ~~~~~~~~~~~~~~~~~
4 warnings and 5 errors generated.
shared:ERROR: '/emsdk_portable/clang/tag-e1.39.4/build_tag-e1.39.4_64/bin/clang -target asmjs-unknown-emscripten -D__EMSCRIPTEN_major__=1 -D__EMSCRIPTEN_minor__=39 -D__EMSCRIPTEN_tiny__=4 -D_LIBCPP_ABI_VERSION=2 -Werror=implicit-function-declaration -Xclang -nostdsysteminc -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/include/libcxx -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/lib/libcxxabi/include -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/include/compat -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/include -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/include/libc -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/lib/libc/musl/arch/emscripten -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/local/include -DBUILD_GL -DENABLE_SCRIPTING -DHAVE_CHMOD -DHAVE_CRC32 -DHAVE_LOCALE -DHAVE_LOCALTIME_R -DHAVE_SETLOCALE -DHAVE_STRDUP -DHAVE_STRNDUP -DHAVE_STRTOF_L -DHAVE_UMASK -DM_CORE_GB -DM_CORE_GBA -DUSE_DEBUGGERS -DUSE_GDB_STUB -DUSE_LZMA -DUSE_PNG -DUSE_PTHREADS -DUSE_SQLITE3 -DUSE_ZLIB -D_7ZIP_PPMD_SUPPPORT -I/home/mgba/src/src -I/home/mgba/src/include -I/home/mgba/src/src/third-party/zlib -I/home/mgba/src/build-wasm/zlib -I/home/mgba/src/src/third-party/libpng -I/home/mgba/src/build-wasm/libpng -I/home/mgba/src/src/third-party/sqlite3 -I/home/mgba/src/src/third-party/lzma -Wall -Wextra -Wno-missing-field-initializers -std=c99 -pthread -DNDEBUG -O2 -c -DEMSCRIPTEN -D__EMSCRIPTEN_PTHREADS__=1 -mllvm -disable-llvm-optzns /home/mgba/src/src/core/cheats.c -Xclang -disable-O0-optnone -Xclang -isystem/emsdk_portable/emscripten/tag-1.39.4/system/include/SDL -c -o CMakeFiles/mgba.dir/src/core/cheats.c.o -emit-llvm' failed (1)
CMakeFiles/mgba.dir/build.make:88: recipe for target 'CMakeFiles/mgba.dir/src/core/cheats.c.o' failed
make[2]: *** [CMakeFiles/mgba.dir/src/core/cheats.c.o] Error 1
CMakeFiles/Makefile2:106: recipe for target 'CMakeFiles/mgba.dir/all' failed
make[1]: *** [CMakeFiles/mgba.dir/all] Error 2
Makefile:138: recipe for target 'all' failed
make: *** [all] Error 2