c++ - 如果我们在不同的进程中使用 read_json，我们是否需要定义 BOOST_SPIRIT_THREADSAFE

Question

我们在不同的进程中使用 read_json()，我们遇到了崩溃。

    #0  0x00007f062ce0d094 in std::mem_fun1_t<int, boost::spirit::classic::impl::grammar_helper_base<boost::spirit::classic::grammar<boost::property_tree::json_parser::json_grammar<boost::property_tree::basic_ptree<std::string, std::string, std::less<std::string> > >, boost::spirit::classic::parser_context<boost::spirit::classic::nil_t> > >, boost::spirit::classic::grammar<boost::property_tree::json_parser::json_grammar<boost::property_tree::basic_ptree<std::string, std::string, std::less<std::string> > >, boost::spirit::classic::parser_context<boost::spirit::classic::nil_t> >*>::operator() (this=0x7f06120f4c90, __p=0x7f05f813faa0, __x=0x7f06120f4df0) at /usr/lib/gcc/x86_64-spcdn-linux-gnu/4.5.2/../../../../include/c++/4.5.2/bits/stl_function.h:605
    #1  0x00007f062ce0c66e in std::binder2nd<std::mem_fun1_t<int, boost::spirit::classic::impl::grammar_helper_base<boost::spirit::classic::grammar<boost::property_tree::json_parser::json_grammar<boost::property_tree::basic_ptree<std::string, std::string, std::less<std::string> > >, boost::spirit::classic::parser_context<boost::spirit::classic::nil_t> > >, boost::spirit::classic::grammar<boost::property_tree::json_parser::json_grammar<boost::property_tree::basic_ptree<std::string, std::string, std::less<std::string> > >, boost::spirit::classic::parser_context<boost::spirit::classic::nil_t> >*> >::operator() (this=0x7f06120f4c90, __x=@0x7f06001446e0) at /usr/lib/gcc/x86_64-spcdn-linux-gnu/4.5.2/../../../../include/c++/4.5.2/backward/binders.h:154
    #2  0x00007f062ce0b87e in std::for_each<std::reverse_iterator<__gnu_cxx::__normal_iterator<boost::spirit::classic::impl::grammar_helper_base<boost::spirit::classic::grammar<boost::property_tree::json_parser::json_grammar<boost::property_tree::basic_ptree<std::string, std::string, std::less<std::string> > >, boost::spirit::classic::parser_context<boost::spirit::classic::nil_t> > >**, std::vector<boost::spirit::classic::impl::grammar_helper_base<boost::spirit::classic::grammar<boost::property_tree::json_parser::json_grammar<boost::property_tree::basic_ptree<std::string, std::string, std::less<std::string> > >, boost::spirit::classic::parser_context<boost::spirit::classic::nil_t> > >*, std::allocator<boost::spirit::classic::impl::grammar_helper_base<boost::spirit::classic::grammar<boost::property_tree::json_parser::json_grammar<boost::property_tree::basic_ptree<std::string, std::string, std::less<std::string> > >, boost::spirit::classic::parser_context<boost::spirit::classic::nil_t> > >*> > > >, std::binder2nd<std::mem_fun1_t<int, boost::spirit::classic::impl::grammar_helper_base<boost::spirit::classic::grammar<boost::property_tree::json_parser::json_grammar<boost::property_tree::basic_ptree<std::string, std::string, std::less<std::string> > >, boost::spirit::classic::parser_context<boost::spirit::classic::nil_t> > >, boost::spirit::classic::grammar<boost::property_tree::json_parser::json_grammar<boost::property_tree::basic_ptree<std::string, std::string, std::less<std::string> > >, boost::spirit::classic::parser_context<boost::spirit::classic::nil_t> >*> > > (__first=..., __last=..., __f=...) at /usr/lib/gcc/x86_64-spcdn-linux-gnu/4.5.2/../../../../include/c++/4.5.2/bits/stl_algo.h:4185
    #3  0x00007f062ce0aa88 in boost::spirit::classic::impl::grammar_destruct<boost::spirit::classic::grammar<boost::property_tree::json_parser::json_grammar<boost::property_tree::basic_ptree<std::string, std::string, std::less<std::string> > >, boost::spirit::classic::parser_context<boost::spirit::classic::nil_t> > > (self=0x7f06120f4df0) at /usr/include/boost/spirit/home/classic/core/non_terminal/impl/grammar.ipp:324
    #4  0x00007f062ce09c5f in boost::spirit::classic::grammar<boost::property_tree::json_parser::json_grammar<boost::property_tree::basic_ptree<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >, boost::spirit::classic::parser_context<boost::spirit::classic::nil_t> >::~grammar (this=0x7f06120f4df0, __in_chrg=<optimized out>) at /usr/include/boost/spirit/home/classic/core/non_terminal/grammar.hpp:52
    #5  0x00007f062ce093f7 in boost::property_tree::json_parser::json_grammar<boost::property_tree::basic_ptree<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >::~json_grammar (this=0x7f06120f4df0, __in_chrg=<optimized out>) at /usr/include/boost/property_tree/detail/json_parser_read.hpp:162
    #6  0x00007f062ce0987f in boost::property_tree::json_parser::read_json_internal<boost::property_tree::basic_ptree<std::string, std::string, std::less<std::string> > > (stream=..., pt=..., filename="") at /usr/include/boost/property_tree/detail/json_parser_read.hpp:310
    #7  0x00007f062ce08eb6 in boost::property_tree::json_parser::read_json<boost::property_tree::basic_ptree<std::string, std::string, std::less<std::string> > > (stream=..., pt=...) at /usr/include/boost/property_tree/json_parser.hpp:45

但是当我在每个使用这个函数的地方定义 BOOST_SPIRIT_THREADSAFE 时，一切都工作正常。但我不明白这一点，因为每个进程都会有不同的地址空间。因此，即使是 Sprit 也烦人地在 grammar.ipp 中创建了一个静态变量，它将在 Spirit 的所有实例之间共享，它将如何在不同进程之间共享？

Answer 1

So even Sprit annoyingly makes a static variable in grammar.ipp that'll be shared amongst all instances of Spirit, how it will be shared across different processes?

事实并非如此。期间。

您的程序可能自己共享一些文件/命名内核对象，但库不会。

虽然这让我担心:

But when I define BOOST_SPIRIT_THREADSAFE at every place where I used this function

您应该全局定义它。那是在所有翻译单元中包含任何 boost header 之前。

如果不这样做至少不能保证所有全局状态都受到保护(想想语言环境字符分类和属性)并且可能很容易违反 One-Definition-Rule