Define static method in source-file with declaration in header-file in C++

I am having a little trouble working with static methods in C++

Example .h:

class IC_Utility {
public:
    IC_Utility();
    ~IC_Utility();

    std::string CP_PStringToString( const unsigned char *outString );
    void CP_StringToPString( std::string& inString, unsigned char *outString, short inMaxLength );
    static void CP_StringToPString( std::string& inString, unsigned char *outString);
    void CP_StringToPString( FxString& inString, FxUChar *outString);

};

Example .cpp:

static void IC_Utility::CP_StringToPString(std::string& inString, unsigned char *outString)
{
    short       length = inString.length();

   if( outString != NULL )
    {
        if( length >= 1 )
            CPLAT::CP_Utility::CP_CopyMemory( inString.c_str(), &outString[ 1 ], length );

            outString[ 0 ] = length;
    }
}

I wanted to make a call like:

IC_Utility::CP_StringToPString(directoryNameString, directoryName );

But I get an error:

error: cannot declare member function 'static void IC_Utility::CP_StringToPString(std::string&, unsigned char*)' to have static linkage

I dont understand why I cannot do this. Can anyone help me understand why and how to achieve what I want?

Solution 1:

Remove static keyword in method definition. Keep it just in your class definition.

static keyword placed in .cpp file means that a certain function has a static linkage, ie. it is accessible only from other functions in the same file.

Solution 2:

Keywords static and virtual should not be repeated in the definition. They should only be used in the class declaration.

Solution 3:

You don't need to have static in function definition