如何解決此一個或多個多重定義符號發現錯誤？

以下專案中的錯誤是什么？

主程式

#include "template_specialization_conflict_test.hpp"

int main()
{
    std::cout << utils::my_template_function(0.555);
    std::cout<<utils::my_template_function<double>(0.555);
    return 0;
}

template_specialization_conflict_test.hpp

#ifndef UTILS__UTILS__UTILS__UTILS
#define UTILS__UTILS__UTILS__UTILS
#include <iostream>

namespace utils
{
    // A generic function
    template <class T>
    T my_template_function(T parameter)
    {
        std::cout << "function template";
        std::cout << parameter;
        return parameter;
    }

    // Template Specialization
    //      A function specialized for double data type
    template <>
    double my_template_function<double>(double parameter)
    {
        std::cout << "function specialization on double";
        std::cout << parameter;
        return parameter;
    }
}
#endif

template_specialization_conflict_test.cpp

#include "template_specialization_conflict_test.hpp"

namespace utils
{
    //empty
}

錯誤

>------ Rebuild All started: Project: template_specialization_conflict_test, Configuration: x64-Debug ------
  [1/1] Cleaning all built files...
  Cleaning... 2 files.
  [1/3] Building CXX object CMakeFiles\template_specialization_conflict_test.dir\main.cpp.obj
  [2/3] Building CXX object CMakeFiles\template_specialization_conflict_test.dir\template_specialization_conflict_test.cpp.obj
  [3/3] Linking CXX executable template_specialization_conflict_test.exe
  FAILED: template_specialization_conflict_test.exe 
  cmd.exe /C "cd . && "C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\bin\cmake.exe" -E vs_link_exe --intdir=CMakeFiles\template_specialization_conflict_test.dir --rc=C:\PROGRA~2\WI3CF2~1\10\bin\10.0.17763.0\x64\rc.exe --mt=C:\PROGRA~2\WI3CF2~1\10\bin\10.0.17763.0\x64\mt.exe --manifests  -- "C:\PROGRA~2\Microsoft Visual Studio\2019\Professional\VC\Tools\MSVC\14.29.30133\bin\Hostx64\x64\link.exe" /nologo CMakeFiles\template_specialization_conflict_test.dir\template_specialization_conflict_test.cpp.obj CMakeFiles\template_specialization_conflict_test.dir\main.cpp.obj  /out:template_specialization_conflict_test.exe /implib:template_specialization_conflict_test.lib /pdb:template_specialization_conflict_test.pdb /version:0.0 /machine:x64 /debug /INCREMENTAL /subsystem:console  kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib && cd ."
  LINK Pass 1: command "C:\PROGRA~2\Microsoft Visual Studio\2019\Professional\VC\Tools\MSVC\14.29.30133\bin\Hostx64\x64\link.exe /nologo CMakeFiles\template_specialization_conflict_test.dir\template_specialization_conflict_test.cpp.obj CMakeFiles\template_specialization_conflict_test.dir\main.cpp.obj /out:template_specialization_conflict_test.exe /implib:template_specialization_conflict_test.lib /pdb:template_specialization_conflict_test.pdb /version:0.0 /machine:x64 /debug /INCREMENTAL /subsystem:console kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib /MANIFEST /MANIFESTFILE:CMakeFiles\template_specialization_conflict_test.dir/intermediate.manifest CMakeFiles\template_specialization_conflict_test.dir/manifest.res" failed (exit code 1169) with the following output:
C:\Users\pc\source\repos\template_specialization_conflict_test\out\build\x64-Debug\main.cpp.obj : error LNK2005: "double __cdecl utils::my_template_function<double>(double)" (??$my_template_function@N@utils@@YANN@Z) already defined in template_specialization_conflict_test.cpp.obj
C:\Users\pc\source\repos\template_specialization_conflict_test\out\build\x64-Debug\template_specialization_conflict_test.exe : fatal error LNK1169: one or more multiply defined symbols found
  ninja: build stopped: subcommand failed.

Rebuild All failed.

我怎樣才能解決這個問題？

uj5u.com熱心網友回復：

我怎樣才能解決這個問題？

您可以通過inline為專業化添加/使用關鍵字來解決這個問題，因此專業化看起來像：

   //note the keyword inline in the below specialization
   template <> inline
    double my_template_function<double>(double parameter)
    {
        std::cout << "function specialization on double";
        std::cout << parameter;
        return parameter;
    }

這可以在這里看到。

解決此問題的第二種方法是將您的專業化移動到源檔案而不是標題中。所以你的template_specialization_conflict_test.cpp看起來像： template_specialization_conflict_test.cpp

#include "template_specialization_conflict_test.hpp"

namespace utils
{
    // Template Specialization
    //      A function specialized for double data type
    template <> 
    double my_template_function<double>(double parameter)
    {
        std::cout << "function specialization on double";
        std::cout << parameter;
        return parameter;
    }
}

該程式可以在這里和這里看到（使用 gcc 和 clang）。

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