Question

我在项目中使用此CROW项目header file

crow_all.h:9382:86: error: no matching function for call to ‘crow::Crow<>::route(const char [20])’
 #define CROW_ROUTE(app, url) app.route<crow::black_magic::get_parameter_tag(url)>(url)
                                                                                      ^
main.cpp:20:5: note: in expansion of macro ‘CROW_ROUTE’
     CROW_ROUTE(app,"/welcome/<uint64_t>")
     ^
crow_all.h:9382:86: note: candidate is:
 #define CROW_ROUTE(app, url) app.route<crow::black_magic::get_parameter_tag(url)>(url)
                                                                                      ^
main.cpp:20:5: note: in expansion of macro ‘CROW_ROUTE’
     CROW_ROUTE(app,"/welcome/<uint64_t>")
     ^
In file included from main.cpp:1:0:
crow_all.h:9423:14: note: template<long unsigned int Tag> typename std::result_of<decltype (& crow::Router:: new_rule_tagged<Tag>)(crow::Router, std::basic_string<char>&&)>::type crow::Crow<Middlewares>::route(std::string&&) [with long unsigned int Tag = Tag; Middlewares = {}]
         auto route(std::string&& rule)
              ^
crow_all.h:9423:14: note:   template argument deduction/substitution failed:
In file included from main.cpp:1:0:
main.cpp:20:5:   in constexpr expansion of ‘crow::black_magic::get_parameter_tag(crow::black_magic::const_str((*"/welcome/<uint64_t>")), 0u)’
crow_all.h:5866:41:   in constexpr expansion of ‘crow::black_magic::get_parameter_tag(s, (p + 1u))’
crow_all.h:5866:41:   in constexpr expansion of ‘crow::black_magic::get_parameter_tag(s, (p + 1u))’
crow_all.h:5866:41:   in constexpr expansion of ‘crow::black_magic::get_parameter_tag(s, (p + 1u))’
crow_all.h:5866:41:   in constexpr expansion of ‘crow::black_magic::get_parameter_tag(s, (p + 1u))’
crow_all.h:5866:41:   in constexpr expansion of ‘crow::black_magic::get_parameter_tag(s, (p + 1u))’
crow_all.h:5866:41:   in constexpr expansion of ‘crow::black_magic::get_parameter_tag(s, (p + 1u))’
crow_all.h:5866:41:   in constexpr expansion of ‘crow::black_magic::get_parameter_tag(s, (p + 1u))’
crow_all.h:5866:41:   in constexpr expansion of ‘crow::black_magic::get_parameter_tag(s, (p + 1u))’
crow_all.h:5866:41:   in constexpr expansion of ‘crow::black_magic::get_parameter_tag(s, (p + 1u))’
crow_all.h:5864:70: error: expression ‘<throw-expression>’ is not a constant-expression
                     throw std::runtime_error("invalid parameter type")
                                                                      ^
In file included from main.cpp:1:0:
crow_all.h:9382:86: note: in template argument for type ‘long unsigned int’ 
 #define CROW_ROUTE(app, url) app.route<crow::black_magic::get_parameter_tag(url)>(url)
                                                                                      ^
main.cpp:20:5: note: in expansion of macro ‘CROW_ROUTE’
     CROW_ROUTE(app,"/welcome/<uint64_t>")
)

下面的代码可以正常使用int类型，但不适用于uint64_t。我收录了#include <cstdint>和#include<cinttypes>

CROW_ROUTE(app,"/welcome/<T>")
    ([](int count) {
        if (count > 400)
            return crow::response(400);
        std::ostringstream os;
        os << count  << " Bottles of beer, Cheers...!!";
        return crow::response(os.str());
    });

// CROW_ROUTE定义如下。

#define CROW_ROUTE(app, url) app.route<crow::black_magic::get_parameter_tag(url)>(url)

模板参数扣除/替换失败：

0 个答案: