将 Boost 与 Emscripten 结合使用

2021-12-24 00:00:00 javascript c++ boost emscripten

我有一个 C++ 项目，我想将其转换为 Web 应用程序.为此，我想使用 Emscripten 来构建项目.

I have a c++ project I would like to convert to a web application. For this purpose, I would like to use Emscripten to build the project.

该项目使用了一些外部库.我设法编译或找到了大多数库的 JavaScript 版本，现在我坚持使用 Boost 版本.实际上我什至不知道如何开始 Boost:他们使用 boostrap 脚本来生成文件来构建库.可以将工具集传递给此脚本，但显然不支持 Emscripten.

The project uses some external libraries. I managed to compile or find the JavaScript version of most libraries and now I am stuck with the Boost ones. Actually I do not even know how to start for Boost: they use a boostrap script to generate the files to build the libraries. It is possible to pass the toolset to this script but Emscripten is obviously not supported.

我的项目使用 Boost 的以下部分:线程、正则表达式、文件系统、信号、系统.如何使用 Emscripten 编译这些库?

My project uses the following parts of Boost: Thread, Regex, FileSystem, Signals, System. How can I compile these libraries using Emscripten?

编辑

按照npclaudiu的回答，我用gcc工具包引导库，然后我编辑project-config.jam来配置编译器，替换:

Following the answer of npclaudiu, I bootstrapped the library with the gcc toolkit, then I edited project-config.jam to configure the compiler, replacing:

# Compiler configuration. This definition will be used unless
# you already have defined some toolsets in your user-config.jam
# file.
if ! gcc in [ feature.values <toolset> ]
{
    using gcc ;
}

与

# Compiler configuration. This definition will be used unless
# you already have defined some toolsets in your user-config.jam
# file.
if ! gcc in [ feature.values <toolset> ]
{
    using gcc : : "/full/path/to/em++" ;
}

现在，输入 ./b2 可以有效地构建库.Boost.Signals 和 Boost.System 编译良好.其他人有一些错误.

Now, typing ./b2 effectively builds the libraries. Boost.Signals and Boost.System compile well. The others have some errors.

Boost.Thread 抱怨:

Boost.Thread complains:

libs/thread/src/pthread/thread.cpp:503:27: error: use of undeclared identifier 'pthread_yield'
        BOOST_VERIFY(!pthread_yield());
                      ^

Boost.Regex 抱怨很多关于 CHAR_BIT 未声明的问题，但这似乎是 emscripten 中的一个问题:

Boost.Regex complains a lot about CHAR_BIT to be undeclared but it seems to be a problem in emscripten:

In file included from libs/regex/build/../src/c_regex_traits.cpp:28:
In file included from ./boost/regex/v4/c_regex_traits.hpp:26:
In file included from ./boost/regex/v4/regex_workaround.hpp:35:
/path/to/emscripten/system/include/libcxx/vector:1989:92: error: use of undeclared identifier 'CHAR_BIT'
static const unsigned __bits_per_word = static_cast<unsigned>(sizeof(__storage_type) * CHAR_BIT);
                                                                                       ^

Boost.FileSystem 似乎也因 emscripten 而失败:

Boost.FileSystem seems to fail due to emscripten too:

In file included from libs/filesystem/src/windows_file_codecvt.cpp:21:
/path/to/emscripten/system/include/libcxx/cwchar:117:9: error: no member named 'FILE' in the global namespace
using ::FILE;
      ~~^

推荐答案

我终于设法用 emscripten 编译了所需的库.这是我遵循的步骤.

I finally managed to compile the needed libraries with emscripten. Here are the steps I followed.

编辑 system/include/libcxx/climits 以添加以下定义(参见 http://github.com/kripken/emscripten/issues/531):

Edit system/include/libcxx/climits to add the following definitions (see http://github.com/kripken/emscripten/issues/531):

#ifndef CHAR_BIT
# define CHAR_BIT __CHAR_BIT__
#endif

#ifndef CHAR_MIN
# define CHAR_MIN (-128)
#endif

#ifndef CHAR_MAX
# define CHAR_MAX 127
#endif

#ifndef SCHAR_MIN
# define SCHAR_MIN (-128)
#endif

#ifndef SCHAR_MAX
# define SCHAR_MAX 127
#endif

#ifndef UCHAR_MAX

# define UCHAR_MAX 255
#endif

#ifndef SHRT_MIN
# define SHRT_MIN (-32767-1)
#endif

#ifndef SHRT_MAX
# define SHRT_MAX 32767
#endif

#ifndef USHRT_MAX
# define USHRT_MAX 65535
#endif

#ifndef INT_MAX
# define INT_MAX __INT_MAX__
#endif

#ifndef INT_MIN
# define INT_MIN (-INT_MAX-1)
# define INT_MIN (-INT_MAX-1)
#endif

#ifndef UINT_MAX
# define UINT_MAX (INT_MAX * 2U + 1)
#endif

#ifndef LONG_MAX
# define LONG_MAX __LONG_MAX__
#endif

#ifndef LONG_MIN
# define LONG_MIN (-LONG_MAX-1)
#endif

#ifndef ULONG_MAX
# define ULONG_MAX (LONG_MAX * 2UL + 1)
#endif

在system/include/libcxx/cwchar

#include <cstdio>

将 Boost 编译为共享库

按照 npclaudiu 的建议，使用 gcc 工具包引导库.然后编辑project-config.jam配置编译器并替换:

# Compiler configuration. This definition will be used unless
# you already have defined some toolsets in your user-config.jam
# file.
if ! gcc in [ feature.values <toolset> ]
{
    using gcc ;
}

与

# Compiler configuration. This definition will be used unless
# you already have defined some toolsets in your user-config.jam
# file.
if ! gcc in [ feature.values <toolset> ]
{
    using gcc : : "/full/path/to/emscripten/em++" ;
}

在 boost/config/posix_features.hpp 中强制 BOOST_HAS_SCHER_YIELD，在第 67 行附近.

Force BOOST_HAS_SCHER_YIELD in boost/config/posix_features.hpp, around the line 67.

然后编译库:./b2 thread regex filesystem signals system

执行以上所有步骤，然后编辑tools/build/v2/tools/gcc.jam并替换:

Do all the above steps, then edit tools/build/v2/tools/gcc.jam and replace:

toolset.flags gcc.archive .AR $(condition) : $(archiver[1]) ;

与

toolset.flags gcc.archive .AR $(condition) : "/full/path/to/emscripten/emar" ;

和

toolset.flags gcc.archive .RANLIB $(condition) : $(ranlib[1]) ;

与

toolset.flags gcc.archive .RANLIB $(condition) :
  "/full/path/to/emscripten/emranlib" ;

编译库:./b2 link=static variant=release threading=single runtime-link=static thread Signals system filesystem regex

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