Emscripten SDL编译失败

Question

我是emscripten的新手；几天前我下载了它，只是为了尝试将游戏移植到JS。

无论如何，经过一些步骤之后，我现在遇到了这个问题(在Ubuntu 16.04 STL上)。通过遵循构建步骤here，首先，我已经使用source ./emsdk_env.sh设置了环境变量，然后我尝试在项目目录中使用emconfigure ./configure配置项目。当检查emscripten需要的工具时，我得到了这个错误：

checking for SDL... no
configure: error: Package requirements (sdl2 >= 2.0.1) were not met:

No package 'sdl2' found

Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.

Alternatively, you may set the environment variables SDL_CFLAGS
and SDL_LIBS to avoid the need to call pkg-config.
See the pkg-config man page for more details.
ERROR:root:Configure step failed with non-zero return code 1! Command line: ['./configure'] at ...

所以我试着用下面的命令来设置这个变量：export PKG_CONFIG_PATH=/usr/lib/x86_64-linux-gnu/pkgconfig/这就是我机器上sdl2.pc实际所在的位置，但是没有帮助。

因此，我设置了emconfigure所需的以下变量：

export SDL_PATH=/home/ustym/Documents/Projects/emsdk/emscripten/1.37.38/system/include/SDL/SDL.h
export SDL_LIBS=/home/ustym/Documents/Projects/emsdk/emscripten/1.37.38/system/include/SDL/SDL.h
export SDL_CFLAGS=/home/ustym/Documents/Projects/emsdk/emscripten/1.37.38/system/include/SDL/SDL.h
export SDLNET_LIBS=/home/ustym/Documents/Projects/emsdk/emscripten/1.37.38/system/include/SDL/SDL.h
export SDLNET_CFLAGS=/home/ustym/Documents/Projects/emsdk/emscripten/1.37.38/system/include/SDL/SDL.h
export SDLMIXER_LIBS=/home/ustym/Documents/Projects/emsdk/emscripten/1.37.38/system/include/SDL/SDL.h
export SDLMIXER_CFLAGS=/home/ustym/Documents/Projects/emsdk/emscripten/1.37.38/system/include/SDL/SDL.h

并重新启动了emconfigure ./configure，它已经完成得很好。因此，下一步是emmake make，它会给我以下错误：

make  all-recursive
make[1]: Entering directory '/home/ustym/Documents/Projects/chocolate-doom-3.0.0'
Making all in textscreen
make[2]: Entering directory '/home/ustym/Documents/Projects/chocolate-doom-3.0.0/textscreen'
Making all in fonts
make[3]: Entering directory '/home/ustym/Documents/Projects/chocolate-doom-3.0.0/textscreen/fonts'
make[3]: Nothing to be done for 'all'.
make[3]: Leaving directory '/home/ustym/Documents/Projects/chocolate-doom-3.0.0/textscreen/fonts'
Making all in .
make[3]: Entering directory '/home/ustym/Documents/Projects/chocolate-doom-3.0.0/textscreen'
  CC       txt_conditional.o
Traceback (most recent call last):
  File "/home/ustym/Documents/Projects/emsdk/emscripten/1.37.38/emcc", line 11, in <module>
    python_selector.run(__file__)
  File "/home/ustym/Documents/Projects/emsdk/emscripten/1.37.38/tools/python_selector.py", line 38, in run
    sys.exit(run_by_import(filename, main) if on_allowed_version() else run_by_subprocess(filename))
  File "/home/ustym/Documents/Projects/emsdk/emscripten/1.37.38/tools/python_selector.py", line 13, in run_by_import
    return getattr(importlib.import_module(os.path.basename(filename)), main)()
  File "/home/ustym/Documents/Projects/emsdk/emscripten/1.37.38/emcc.py", line 1345, in run
    assert header.endswith(HEADER_ENDINGS), 'if you have one header input, we assume you want to precompile headers, and cannot have source files or other inputs as well: ' + str(headers) + ' : ' + header
AssertionError: if you have one header input, we assume you want to precompile headers, and cannot have source files or other inputs as well: ['/home/ustym/Documents/Projects/emsdk/emscripten/1.37.38/system/include/SDL/SDL.h', 'txt_conditional.c'] : txt_conditional.c
Makefile:447: recipe for target 'txt_conditional.o' failed
make[3]: *** [txt_conditional.o] Error 1
make[3]: Leaving directory '/home/ustym/Documents/Projects/chocolate-doom-3.0.0/textscreen'
Makefile:467: recipe for target 'all-recursive' failed
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory '/home/ustym/Documents/Projects/chocolate-doom-3.0.0/textscreen'
Makefile:585: recipe for target 'all-recursive' failed
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory '/home/ustym/Documents/Projects/chocolate-doom-3.0.0'
Makefile:438: recipe for target 'all' failed
make: *** [all] Error 2

这意味着，我假设，SDL_PATH，SDL_LIBS，SDL_CFLAGS...变量设置不正确。或者我只需要在SDL目录中预编译头文件。

最后一件事:如果我跳过设置SDL变量和配置步骤，只启动emmake make，编译就会正常进行，但是emcc命令会为所有生成的.o文件提供WARNING:root: .o is not valid LLVM bitcode。这实际上是有道理的。

所以我被困在这里了。有人能告诉我如何为emscripten设置正确的PKG_CONFIG_PATH，或者我是否真的需要在SDL目录中预编译头文件？谢谢!

Answer 1

首先，设置PKG_CONFIG_PATH、include或者更糟糕的是库目录(-I和-L)来托管库的目录对我来说是个糟糕的主意: Emscripten目标文件包含LLVM位代码(而不是主机代码)，它的.so文件AFAIK也包含位代码。是位代码被转换为JS，而不是宿主机器代码。因此，您需要自己使用Emscripten来构建程序的依赖项(并且最好不要将其安装到主机系统中)。幸运的是，有一些官方的Emscripten端口(请参阅here)以了解详细信息。

SDL2有自己的seems实现(您可能尝试手动使用)，但您的程序似乎需要Emscripten。好消息:您可能只需要在configureing时将-s USE_SDL=2传递给CFLAGS和LDFLAGS (有关SDL2端口的信息，请参阅上面的链接后面的内容)。坏消息:有些东西可能没有完全移植。但在某种程度上，我成功地使用了它。

当您在主机上使用configured并使用emmake时，您可能已经将编译器路径以及由emconfigure调整的其他参数和emmake已经烘焙到由./configure生成的Makefile中，而不是由emconfigure控制，因此主机gcc/clang只生成了机器码。