Visual c ++未解析的extern符号错误 [英] Visual c++ Unresolved extern symbol error

问题描述

我正在编译调用fitsio.h的源代码。来自fit库的文件，然后在fitsio.h中，另一个头文件名为longname.h，这个ffclos，ffgpxv all在longnam.h中定义。 。虽然我正在编译它的给出错误信息：


usimage.cpp

生成代码...

链接...

创建库.\Output / gci2.lib和object .\Output / gci2.exp

cam_simulator.obj：错误LNK2001：未解析的外部符号_ffclos

cam_simulator.obj：错误LNK2001：未解析的外部符号_ffgpxv

cam_simulator.obj：错误LNK2001：未解析的外部符号_ffthdu

cam_simulator.obj：错误LNK2001：未解析的外部符号_ffgisz

cam_simulator.obj：错误LNK2001：未解析的外部符号_ffgidm

cam_simulator.obj：错误LNK2001：未解析的外部符号_ffghdt

cam_simulator.obj：错误LNK2001：未解析的外部符号_ffdkopn

guide_routines.obj：错误LNK2001：未解析的外部符号" float __cdecl CalcSlope（类DoubleArray）" （？CalcSlope @@ YAMVDoubleArray @@@ Z）

。\\\ release / gci2.dll：致命错误LNK1120：8个未解析的外部

执行link.exe时出错。

PixCel.exe - 9个错误，3个警告

I am compiling my source code which is calling "fitsio.h" file from fits library , and then in fitsio.h another header file is getting called named longname.h , this ffclos , ffgpxv all are defined in "longnam.h" .While I am compiling its giving error message :

usimage.cpp
Generating Code...
Linking...
Creating library .\Output/gci2.lib and object .\Output/gci2.exp
cam_simulator.obj : error LNK2001: unresolved external symbol _ffclos
cam_simulator.obj : error LNK2001: unresolved external symbol _ffgpxv
cam_simulator.obj : error LNK2001: unresolved external symbol _ffthdu
cam_simulator.obj : error LNK2001: unresolved external symbol _ffgisz
cam_simulator.obj : error LNK2001: unresolved external symbol _ffgidm
cam_simulator.obj : error LNK2001: unresolved external symbol _ffghdt
cam_simulator.obj : error LNK2001: unresolved external symbol _ffdkopn
guide_routines.obj : error LNK2001: unresolved external symbol "float __cdecl CalcSlope(class DoubleArray)" (?CalcSlope@@YAMVDoubleArray@@@Z)
.\Release/gci2.dll : fatal error LNK1120: 8 unresolved externals
Error executing link.exe.
PixCel.exe - 9 error(s), 3 warning(s)

推荐答案

当你在编译链接时是链接器错误。


函数ffclos等没有在longnam.h中定义（至少我怀疑它们是）在longnam.h中声明它们。

编译器只需要声明，告诉它函数存在于某处，使用它们编译文件。但链接器确实需要定义才能构建使用这些函数的程序。


通常，第三方函数的定义将存在于库文件中（.lib ）虽然声明存在于标题（.h）中。


导致此错误的最可能原因是您已经失败/忘记将所需的库添加到链接中。 />

在项目属性中查找链接器选项。

Not while you are compiling, while you are linking those are linker errors.

The functions ffclos etc are not defined in longnam.h (at least I doubt they are) they are declared in longnam.h.

The compiler only needs the declarations, which tell it that the function exists somewhere, to compile a file using them. however the linker does need the definitions in order to be able to build a program that uses the functions.

Normally the definitions for a 3rd party function will exist in the library file (.lib) while the declarations exist in the header (.h).

The most likely cause for this error is that you have failed/forgotten to add the required library to the link.

Look for linker options in your project properties.

@Banfa


非常感谢你清理我的概念，这里发生了什么，它完成了检查所有文件，所以我认为它在编译期间没有找到错误。然后当它与库链接


链接...

创建库。\ Output / gci2.lib和object。\ Output / gci2.exp

cam_simulator.obj：错误LNK2001：未解析的外部符号_ffclos

cam_simulator.obj：错误LNK2001：未解析的外部符号_ffgpxv

" ;


它产生错误，我在项目链接器属性中正确链接..是否需要任何其他设置或链接？

@Banfa
thank you very much for clearing my concepts , here what happening , its completing checking all the file , so i think it doesnt find an error during compilation . Then when it is linking with library

"Linking...
Creating library .\Output/gci2.lib and object .\Output/gci2.exp
cam_simulator.obj : error LNK2001: unresolved external symbol _ffclos
cam_simulator.obj : error LNK2001: unresolved external symbol _ffgpxv
"

its generating the error , i have linked properly in my project linker property ..Is it require any other setting or linking ?

是有一些库（.lib）或源文件（.c）与longnam.h一起需要包含在项目中。

Yes there is some library (.lib) or source file (.c) that goes along with longnam.h and needs including into the project.

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