错误 C2894：不能将模板声明为具有“C”链接

Question

我明白了

error C2894: templates cannot be declared to have 'C' linkage

当我尝试编译我的 C++ 项目时。

所有错误都指向 vc++ 文件

1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(32): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(120): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(133): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(256): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(279): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(375): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(474): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(486): error C2039: 'memcmp' : is not a member of '`global namespace''
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(486): error C3861: 'memcmp': identifier not found
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(491): error C2039: 'strlen' : is not a member of '`global namespace''
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(491): error C3861: 'strlen': identifier not found
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(511): error C2039: 'memchr' : is not a member of '`global namespace''
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(511): error C3861: 'memchr': identifier not found
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(522): error C2039: 'memset' : is not a member of '`global namespace''
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(522): error C3861: 'memset': identifier not found
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(568): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(571): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(574): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(577): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(580): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(583): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(586): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(589): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(592): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(596): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(600): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(604): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(608): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(611): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(614): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(617): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(622): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(625): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(628): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\limits(80): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\limits(133): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\limits(139): error C2894: templates cannot be declared to have 'C' linkage
1>c:\program files\microsoft visual studio 10.0\vc\include\limits(139): fatal error C1003: error count exceeds 100; stopping compilation

这些错误是什么以及如何解决它们。 这些错误在我从未看到这些错误之前突然出现。

在我正在进行的项目中，我从不使用 extern C

谢谢

Answer 1

当您在extern "C" 命令中包含头文件时会发生此错误

extern "C"
{

    #include "Header.h"
}

只需将#include "cs.h" 包含在extern c 之外即可。

#include "Header.h"
extern "C"
{

    //code

}

Answer 2

如果不显示您的来源，很难为您提供任何帮助，但 MSDN for error #2894 和 some other portals 上的信息非常简单：

// C2894.cpp
extern "C" {
   template<class T> class stack {};   // C2894 fail

   template<class T> void f(const T &aT) {}   // C2894
}

也许您的文件名为 .c 而不是 .cpp，或者切换了一些编译标志。

Answer 3

如果你写过这个……

extern "C"
{
    #include "Header.h"
}

比写成

extern "C++"
{
    #include "Header.h"
}

当您尝试在 C++ 中引用 C 函数时，它会通过错误来避免您只是将其引用到 C++，以便您可以在 .CXX 或 .Cpp 函数中引用它

Answer 4

有时原因很简单：您的项目中的某些文件名与默认设置的项目中包含的标准 C/C++ 库中的 VS 相同。 例如，string.h。这个事实将产生错误。只需重命名这些文件，您就可以成功构建您的项目。