Do we use dllexport when no cpp file is involved?

Question

Hi,
I test the following two .h files.  Both of them are placed in a slave dll.  The master dll includes them and use "struct A".  They both work.  So, my question is when we should be concerned about export/import.  It seems
to me that we should export (dllexprt) an object only if there is a .cpp file involved.  If there is only .h file involved as shown in the examples below, no exporting is needed.  Is it correct?  Besides, is there any difference at all between
File1.h and File2.h?  Thanks for any input.  
// File1.h
struct A
  A() : data(-1) { }
  ~A() {}
  int data;
// File2.h
#ifdef  __Universe
#define ExportedByUniverse __declspec(dllexport)
#else
#define ExportedByUniverse __declspec(dllimport)
struct ExportedByUniverse A
  A() : data(-1) { }
  ~A() {}
  int data;
JD

Answer 1

On 2/3/2015 9:51 PM, jdyng77 wrote:
I test the following two .h files.  Both of them are placed in a slave dll.  The master dll includes them and use "struct A".  They both work.  So, my question is when we should be concerned about export/import.  It seems
to me that we should export (dllexprt) an object only if there is a .cpp file involved.  If there is only .h file involved as shown in the examples below, no exporting is needed.  Is it correct?
In a sense. The code for struct A ends up embedded into the master DLL (thanks to it being available in the headers). The slave DLL isn't being used at all, so it doesn't matter whether or not it exports anything.
Igor Tandetnik