安装依赖
Node.js(0.8 or above; 0.10.17 or above to run websocket-using servers in node):
Python2.x (2.7.3 or above preferred)
Java(1.6.0_31 or later). Java is optional. It is required to use theClosure Compiler(in order to minify your code).
Gitclient. Git is required if building tools from source.
Fastcomp(Emscripten’s fork of LLVM and Clang)
参考链接地址：Manually Building Emscripten on Mac OS X
To build the Fastcomp code from source:
Create a directory to store the build. It doesn’t matter where, because Emscripten gets the information from thecompiler configuration file (~/.emscripten). We show how to update this file later in these instructions:
mkdirmyfastcompcdmyfastcomp
Clone the fastcomp LLVM repository (https://github.com/kripken/emscripten-fastcomp):
gitclonehttps://github.com/kripken/emscripten-fastcomp
Clone thekripken/emscripten-fastcomp-clangrepository intoemscripten-fastcomp/tools/clang:
cdemscripten-fastcompgitclonehttps://github.com/kripken/emscripten-fastcomp-clang tools/clang
Warning
Youmustclone it into a directory namedclangas shown, so thatClangis present intools/clang!
Create abuilddirectory (inside theemscripten-fastcompdirectory) and then navigate into it:
mkdirbuildcdbuild
Configure the build usingeithercmakeor theconfigurescript:
Usingcmake:
cmake..-DCMAKE_BUILD_TYPE=Release-DLLVM_TARGETS_TO_BUILD="X86;JSBackend"-DLLVM_INCLUDE_EXAMPLES=OFF-DLLVM_INCLUDE_TESTS=OFF-DCLANG_INCLUDE_EXAMPLES=OFF-DCLANG_INCLUDE_TESTS=OFF
Note
On Windows add the-G"VisualStudio10Win64"directive to build using Visual Studio (Visual Studio 2011 and 2012 do NOT work).
Usingconfigure(Linux/Mac only):
../configure--enable-optimized--disable-assertions--enable-targets=host,js
Determine the number of available cores on your system (Emscripten can run many operations in parallel, so using more cores may have a significant impact on compilation time):
On Mac OS X you can get the number of cores using:Apple menu | About this mac | More info | System report. TheHardware overviewon the resulting dialog includes aTotal number of coresentry.
On Linux you can find the number of cores by entering the following command on the terminal:cat/proc/cpuinfo|grep"^cpucores"|uniq.
On Windows the number of cores is listed on theTask Manager | Performance Tab. You can open theTask Managerby enteringCtrl + Shift + Escfrom the Desktop.
Callmaketo build the sources, specifying the number of available cores:
make-j4
Note
If the build completes successfully,clang,clang++, and a number of other files will be created in the release directory (/build/Release/bin).
The final step is to update the~/.emscriptenfile, specifying the location offastcompin theLLVM_ROOTvariable.
Note
If you’re building thewholeof Emscripten from source, following the platform-specific instructions inBuilding Emscripten from Source, you won’t yet have Emscripten installed. In this case, skip this step and return to those instructions.
If you already have an Emscripten environment (for example if you’re building Fastcomp using the SDK), then setLLVM_ROOTto the location of theclangbinary under thebuilddirectory. This will be something like/build/Release/binor/build/bin:
```
vim ~/.emscripten
```
修改 LLVM_ROOT到指定的文件目录
LLVM_ROOT = '/usr/local/myfastcomp/emscripten-fastcomp/build/bin' # directory
TheEmscripten code, from GitHub
clone emscripten项目到本地
```
git clone https://github.com/kripken/emscripten
cd emscripten
npm install
```
测试是否各依赖环境已经正确安装成功
在emscripten目录下运行
```
./emcc tests/hello_world.cpp
```
如果没有报错则会在同目录下找到一个新文件a.out.js
现在可以通过nodejs来运行a.out.js这个文件了
```
node a.out.js
```
会在控制台打印出
```
hello, world!
```
通过browserify编译使之能在浏览器运行
安装browserify
```
sudo npm install browserify -g
```
编译a.out.js文件
```
browserify a.out.js > test.js
```
现在可以在网页中引入test.js文件
```
<script src='test.js'></script>
```
打开控制台可以看到
```
hello world
```
可以在输出的时候直接指定声称为浏览器端运行的代码，
./emcc tests/hello_world.cpp -o test.html
在js中调用c++/c写的函数
Module.ccap("function_name", return_type, arg_type, arg)
使用emscritpen输入代码优化
./emcc tests/hello-test.cpp -o function.js
代码是通过指定优化的优化参数运行时，EMCC。级别包括：-O0（不优化），-O1，-O2，-Os，-OZ和-O3
添加setting
-s EXPORTED_FUNCTIONS="['_uncompress']" //到处函数
-s NO_FILESYSTEM=1 //0 在代码中包含文件系统代码， 1在代码中不包含文件系统代码
-s EXPORTED_RUNTIME_METHODS //到处可以在模块中使用的函数
[
'FS_createFolder',
'FS_createPath',
'FS_createDataFile',
'FS_createPreloadedFile',
'FS_createLazyFile',
'FS_createLink',
'FS_createDevice',
'FS_unlink',
'Runtime',
'ccall',
'cwrap',
'setValue',
'getValue',
'ALLOC_NORMAL',
'ALLOC_STACK',
'ALLOC_STATIC',
'ALLOC_DYNAMIC',
'ALLOC_NONE',
'allocate',
'getMemory',
'Pointer_stringify',
'AsciiToString',
'stringToAscii',
'UTF8ArrayToString',
'UTF8ToString',
'stringToUTF8Array',
'stringToUTF8',
'lengthBytesUTF8',
'stackTrace',
'addOnPreRun',
'addOnInit',
'addOnPreMain',
'addOnExit',
'addOnPostRun',
'intArrayFromString',
'intArrayToString',
'writeStringToMemory',
'writeArrayToMemory',
'writeAsciiToMemory',
'addRunDependency',
'removeRunDependency',
];
编译多个c++/c文件到一个js中
# Sub-optimal - JavaScript optimizations are omitted
./emcc -O2 a.cpp -o a.bc
./emcc -O2 b.cpp -o b.bc
./emcc a.bc b.bc -o project.js
# Sub-optimal - LLVM optimizations omitted
./emcc a.cpp -o a.bc
./emcc b.cpp -o b.bc
./emcc -O2 a.bc b.bc -o project.js
# Broken! Different JavaScript and LLVM optimisations used.
./emcc -O1 a.cpp -o a.bc
./emcc -O2 b.cpp -o b.bc
./emcc -O3 a.bc b.bc -o project.js
# Correct. The SAME LLVM and JavaScript options are provided at both levels.
./emcc -O2 a.cpp -o a.bc
./emcc -O2 b.cpp -o b.bc
./emcc -O2 a.bc b.bc -o project.js
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