inline function linker error

Question

I am trying to use inline member functions of a particular class. For example the function declaration and implementation without inlining is as such:

in the header file:

int GetTplLSize(); 

in the .cpp file:

int NeedleUSsim::GetTplLSize() {     return sampleDim[1]; } 

For some reason if I put the "inline" keyword in either one of the implementation and declaration, as well as in both places, I get linker errors as shown:

  Creating library C:\DOCUME~1\STANLEY\LOCALS~1\TEMP\MEX_HN~1\templib.x and object C:\DOCUME~1\STANLEY\LOCALS~1\TEMP\MEX_HN~1\templib.exp  mexfunction.obj : error LNK2019: unresolved external symbol "public: int __thiscall NeedleUSsim::GetTplLSize(void)" (?GetTplLSize@NeedleUSsim@@QAEHXZ) referenced in function _mexFunction  mexfunction.mexw32 : fatal error LNK1120: 1 unresolved externals     C:\PROGRA~1\MATLAB\R2008B\BIN\MEX.PL: Error: Link of 'mexfunction.mexw32' failed.  

What needs to be in order to get rid of this error (i.e. what am I doing wrong in terms of making these inline member functions)?

Answer 1

You need to put function definition into the header then. The simplest way to hint the compiler to inline is to include method body in the class declaration like:

 class NeedleUSsim {   // ...   int GetTplLSize() const { return sampleDim[1]; }   // ... }; 

or, if you insist on separate declaration and definition:

 class NeedleUSsim {   // ...   int GetTplLSize() const;   // ... };  inline int NeedleUSsim::GetTplLSize() const { return sampleDim[1]; } 

The definition has to be visible in each translation unit that uses that method.