[Regression] drogon::getVersion() compilation failed

[kotori2]

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Please create a new issue only if you think you have found a bug or if have a feature request/enhancement.

Describe the bug error LNK2001: unresolved external symbol class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl drogon::getVersion(void)" (?getVersion@drogon@@YA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ)

To Reproduce Steps to reproduce the behavior:

1. Install drogon 1.7.5 with vcpkg.json
2. compile the following code:

#include <drogon/drogon.h>

int main() {
    LOG_INFO << drogon::getVersion();
    return 0;
}

Expected behavior Program will compile

Desktop (please complete the following information):

• OS: Windows 11 21H2 22000.556
• Browser N/A

Additional context Compiler: MSVC 19.31.31104

[clapfootrohun]

I just started using the library and am experiencing a similar issue.

I've downloaded drogon 1.7.5 via vcpkg. I've followed the windows installation instructions. I setup a project using dragon_ctl. I'm using VS2019 with C++ 20

I'm getting a linker error when calling into certain functions like drogon::getVersion() or HttpResponse::getBody()

Error	LNK2019	unresolved external symbol "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl drogon::getVersion(void)" (?getVersion@drogon@@YA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ) referenced in function main

I've also tried using C++14 and boost and got the same linker error. I have added the following to the path environment variables: vcpkg\installed\x64-windows\bin, lib and include

OS: Windows 10 10.0.19043 Visual Studio 2019 v16.11.7 MSVC 14.29.30133

[an-tao]

the DROGON_EXPORT macro is missed with the getVersion function, I'll fix this issue by adding the macro.

[clapfootrohun]

Thank you for the prompt response and fix. Any idea about the linker error with HttpResponse::getBody()?

Error	LNK2019	unresolved external symbol "__declspec(dllimport) public: class boost::basic_string_view<char,struct std::char_traits<char> > __cdecl drogon::HttpResponse::getBody(void)const " (__imp_?getBody@HttpResponse@drogon@@QEBA?AV?$basic_string_view@DU?$char_traits@D@std@@@boost@@XZ) referenced in function main	

This seems to be a problem only when compiling with C++ 14 and boost. I don't see this error when using C++20. However my main project is stuck on C++14 for now.

[an-tao]

Thank you for the prompt response and fix. Any idea about the linker error with HttpResponse::getBody()?

Error	LNK2019	unresolved external symbol "__declspec(dllimport) public: class boost::basic_string_view<char,struct std::char_traits<char> > __cdecl drogon::HttpResponse::getBody(void)const " (__imp_?getBody@HttpResponse@drogon@@QEBA?AV?$basic_string_view@DU?$char_traits@D@std@@@boost@@XZ) referenced in function main	

This seems to be a problem only when compiling with C++ 14 and boost. I don't see this error when using C++20. However my main project is stuck on C++14 for now.

C++ 14 was checked in github CI actions. Try to clean your build folder and re-cmake, rebuild every thing.